btrfs-progs: check: fix the return value bug of cmd_check()
[platform/upstream/btrfs-progs.git] / cmds-check.c
index 127ac97..14816bd 100644 (file)
@@ -41,6 +41,7 @@
 #include "rbtree-utils.h"
 #include "backref.h"
 #include "ulist.h"
+#include "hash.h"
 
 enum task_position {
        TASK_EXTENTS,
@@ -67,7 +68,6 @@ static u64 data_bytes_referenced = 0;
 static int found_old_backref = 0;
 static LIST_HEAD(duplicate_extents);
 static LIST_HEAD(delete_items);
-static int repair = 0;
 static int no_holes = 0;
 static int init_extent_tree = 0;
 static int check_data_csum = 0;
@@ -75,6 +75,15 @@ static struct btrfs_fs_info *global_info;
 static struct task_ctx ctx = { 0 };
 static struct cache_tree *roots_info_cache = NULL;
 
+enum btrfs_check_mode {
+       CHECK_MODE_ORIGINAL,
+       CHECK_MODE_LOWMEM,
+       CHECK_MODE_UNKNOWN,
+       CHECK_MODE_DEFAULT = CHECK_MODE_ORIGINAL
+};
+
+static enum btrfs_check_mode check_mode = CHECK_MODE_DEFAULT;
+
 struct extent_backref {
        struct list_head list;
        unsigned int is_data:1;
@@ -84,6 +93,11 @@ struct extent_backref {
        unsigned int broken:1;
 };
 
+static inline struct extent_backref* to_extent_backref(struct list_head *entry)
+{
+       return list_entry(entry, struct extent_backref, list);
+}
+
 struct data_backref {
        struct extent_backref node;
        union {
@@ -99,6 +113,11 @@ struct data_backref {
        u32 found_ref;
 };
 
+static inline struct data_backref* to_data_backref(struct extent_backref *back)
+{
+       return container_of(back, struct data_backref, node);
+}
+
 /*
  * Much like data_backref, just removed the undetermined members
  * and change it to use list_head.
@@ -122,6 +141,14 @@ struct tree_backref {
        };
 };
 
+static inline struct tree_backref* to_tree_backref(struct extent_backref *back)
+{
+       return container_of(back, struct tree_backref, node);
+}
+
+/* Explicit initialization for extent_record::flag_block_full_backref */
+enum { FLAG_UNSET = 2 };
+
 struct extent_record {
        struct list_head backrefs;
        struct list_head dups;
@@ -138,7 +165,7 @@ struct extent_record {
        u64 info_objectid;
        u32 num_duplicates;
        u8 info_level;
-       int flag_block_full_backref;
+       unsigned int flag_block_full_backref:2;
        unsigned int found_rec:1;
        unsigned int content_checked:1;
        unsigned int owner_ref_checked:1;
@@ -149,20 +176,30 @@ struct extent_record {
        unsigned int wrong_chunk_type:1;
 };
 
+static inline struct extent_record* to_extent_record(struct list_head *entry)
+{
+       return container_of(entry, struct extent_record, list);
+}
+
 struct inode_backref {
        struct list_head list;
        unsigned int found_dir_item:1;
        unsigned int found_dir_index:1;
        unsigned int found_inode_ref:1;
-       unsigned int filetype:8;
+       u8 filetype;
+       u8 ref_type;
        int errors;
-       unsigned int ref_type;
        u64 dir;
        u64 index;
        u16 namelen;
        char name[0];
 };
 
+static inline struct inode_backref* to_inode_backref(struct list_head *entry)
+{
+       return list_entry(entry, struct inode_backref, list);
+}
+
 struct root_item_record {
        struct list_head list;
        u64 objectid;
@@ -253,6 +290,11 @@ struct root_backref {
        char name[0];
 };
 
+static inline struct root_backref* to_root_backref(struct list_head *entry)
+{
+       return list_entry(entry, struct root_backref, list);
+}
+
 struct root_record {
        struct list_head backrefs;
        struct cache_extent cache;
@@ -310,6 +352,23 @@ struct root_item_info {
        struct cache_extent cache_extent;
 };
 
+/*
+ * Error bit for low memory mode check.
+ *
+ * Currently no caller cares about it yet.  Just internal use for error
+ * classification.
+ */
+#define BACKREF_MISSING                (1 << 0) /* Backref missing in extent tree */
+#define BACKREF_MISMATCH       (1 << 1) /* Backref exists but does not match */
+#define BYTES_UNALIGNED                (1 << 2) /* Some bytes are not aligned */
+#define REFERENCER_MISSING     (1 << 3) /* Referencer not found */
+#define REFERENCER_MISMATCH    (1 << 4) /* Referenceer found but does not match */
+#define CROSSING_STRIPE_BOUNDARY (1 << 4) /* For kernel scrub workaround */
+#define ITEM_SIZE_MISMATCH     (1 << 5) /* Bad item size */
+#define UNKNOWN_TYPE           (1 << 6) /* Unknown type */
+#define ACCOUNTING_MISMATCH    (1 << 7) /* Used space accounting error */
+#define CHUNK_TYPE_MISMATCH    (1 << 8)
+
 static void *print_status_check(void *p)
 {
        struct task_ctx *priv = p;
@@ -344,6 +403,18 @@ static int print_status_return(void *p)
        return 0;
 }
 
+static enum btrfs_check_mode parse_check_mode(const char *str)
+{
+       if (strcmp(str, "lowmem") == 0)
+               return CHECK_MODE_LOWMEM;
+       if (strcmp(str, "orig") == 0)
+               return CHECK_MODE_ORIGINAL;
+       if (strcmp(str, "original") == 0)
+               return CHECK_MODE_ORIGINAL;
+
+       return CHECK_MODE_UNKNOWN;
+}
+
 /* Compatible function to allow reuse of old codes */
 static u64 first_extent_gap(struct rb_root *holes)
 {
@@ -476,7 +547,7 @@ static int del_file_extent_hole(struct rb_root *holes,
                return -EEXIST;
 
        /*
-        * Now there will be no overflap, delete the hole and re-add the
+        * Now there will be no overlap, delete the hole and re-add the
         * split(s) if they exists.
         */
        if (start > hole->start) {
@@ -589,6 +660,7 @@ static struct inode_record *clone_inode_rec(struct inode_record *orig_rec)
        struct inode_backref *tmp;
        struct orphan_data_extent *src_orphan;
        struct orphan_data_extent *dst_orphan;
+       struct rb_node *rb;
        size_t size;
        int ret;
 
@@ -621,10 +693,21 @@ static struct inode_record *clone_inode_rec(struct inode_record *orig_rec)
                list_add_tail(&dst_orphan->list, &rec->orphan_extents);
        }
        ret = copy_file_extent_holes(&rec->holes, &orig_rec->holes);
-       BUG_ON(ret < 0);
+       if (ret < 0)
+               goto cleanup_rb;
 
        return rec;
 
+cleanup_rb:
+       rb = rb_first(&rec->holes);
+       while (rb) {
+               struct file_extent_hole *hole;
+
+               hole = rb_entry(rb, struct file_extent_hole, node);
+               rb = rb_next(rb);
+               free(hole);
+       }
+
 cleanup:
        if (!list_empty(&rec->backrefs))
                list_for_each_entry_safe(orig, tmp, &rec->backrefs, list) {
@@ -746,9 +829,9 @@ static void print_ref_error(int errors)
        if (errors & REF_ERR_DUP_INODE_REF)
                fprintf(stderr, ", dup inode ref");
        if (errors & REF_ERR_INDEX_UNMATCH)
-               fprintf(stderr, ", index unmatch");
+               fprintf(stderr, ", index mismatch");
        if (errors & REF_ERR_FILETYPE_UNMATCH)
-               fprintf(stderr, ", filetype unmatch");
+               fprintf(stderr, ", filetype mismatch");
        if (errors & REF_ERR_NAME_TOO_LONG)
                fprintf(stderr, ", name too long");
        if (errors & REF_ERR_NO_ROOT_REF)
@@ -831,8 +914,7 @@ static void free_inode_rec(struct inode_record *rec)
                return;
 
        while (!list_empty(&rec->backrefs)) {
-               backref = list_entry(rec->backrefs.next,
-                                    struct inode_backref, list);
+               backref = to_inode_backref(rec->backrefs.next);
                list_del(&backref->list);
                free(backref);
        }
@@ -855,7 +937,7 @@ static void maybe_free_inode_rec(struct cache_tree *inode_cache,
        struct cache_extent *cache;
        struct inode_backref *tmp, *backref;
        struct ptr_node *node;
-       unsigned char filetype;
+       u8 filetype;
 
        if (!rec->found_inode_item)
                return;
@@ -986,7 +1068,7 @@ static struct inode_backref *get_inode_backref(struct inode_record *rec,
 static int add_inode_backref(struct cache_tree *inode_cache,
                             u64 ino, u64 dir, u64 index,
                             const char *name, int namelen,
-                            int filetype, int itemtype, int errors)
+                            u8 filetype, u8 itemtype, int errors)
 {
        struct inode_record *rec;
        struct inode_backref *backref;
@@ -1389,7 +1471,7 @@ static int process_dir_item(struct btrfs_root *root,
        u32 data_len;
        int error;
        int nritems = 0;
-       int filetype;
+       u8 filetype;
        struct btrfs_dir_item *di;
        struct inode_record *rec;
        struct cache_tree *root_cache;
@@ -1830,8 +1912,14 @@ static int check_child_node(struct btrfs_root *root,
        return ret;
 }
 
+struct node_refs {
+       u64 bytenr[BTRFS_MAX_LEVEL];
+       u64 refs[BTRFS_MAX_LEVEL];
+};
+
 static int walk_down_tree(struct btrfs_root *root, struct btrfs_path *path,
-                         struct walk_control *wc, int *level)
+                         struct walk_control *wc, int *level,
+                         struct node_refs *nrefs)
 {
        enum btrfs_tree_block_status status;
        u64 bytenr;
@@ -1844,12 +1932,20 @@ static int walk_down_tree(struct btrfs_root *root, struct btrfs_path *path,
 
        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);
-       ret = btrfs_lookup_extent_info(NULL, root,
+
+       if (path->nodes[*level]->start == nrefs->bytenr[*level]) {
+               refs = nrefs->refs[*level];
+               ret = 0;
+       } else {
+               ret = btrfs_lookup_extent_info(NULL, root,
                                       path->nodes[*level]->start,
                                       *level, 1, &refs, NULL);
-       if (ret < 0) {
-               err = ret;
-               goto out;
+               if (ret < 0) {
+                       err = ret;
+                       goto out;
+               }
+               nrefs->bytenr[*level] = path->nodes[*level]->start;
+               nrefs->refs[*level] = refs;
        }
 
        if (refs > 1) {
@@ -1880,10 +1976,19 @@ static int walk_down_tree(struct btrfs_root *root, struct btrfs_path *path,
                bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
                blocksize = root->nodesize;
-               ret = btrfs_lookup_extent_info(NULL, root, bytenr, *level - 1,
-                                              1, &refs, NULL);
-               if (ret < 0)
-                       refs = 0;
+
+               if (bytenr == nrefs->bytenr[*level - 1]) {
+                       refs = nrefs->refs[*level - 1];
+               } else {
+                       ret = btrfs_lookup_extent_info(NULL, root, bytenr,
+                                       *level - 1, 1, &refs, NULL);
+                       if (ret < 0) {
+                               refs = 0;
+                       } else {
+                               nrefs->bytenr[*level - 1] = bytenr;
+                               nrefs->refs[*level - 1] = refs;
+                       }
+               }
 
                if (refs > 1) {
                        ret = enter_shared_node(root, bytenr, refs,
@@ -1976,7 +2081,7 @@ static int check_root_dir(struct inode_record *rec)
                goto out;
        if (list_empty(&rec->backrefs))
                goto out;
-       backref = list_entry(rec->backrefs.next, struct inode_backref, list);
+       backref = to_inode_backref(rec->backrefs.next);
        if (!backref->found_inode_ref)
                goto out;
        if (backref->index != 0 || backref->namelen != 2 ||
@@ -2082,7 +2187,7 @@ static int add_missing_dir_index(struct btrfs_root *root,
                                 struct inode_record *rec,
                                 struct inode_backref *backref)
 {
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_trans_handle *trans;
        struct btrfs_dir_item *dir_item;
        struct extent_buffer *leaf;
@@ -2093,27 +2198,22 @@ static int add_missing_dir_index(struct btrfs_root *root,
        u32 data_size = sizeof(*dir_item) + backref->namelen;
        int ret;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
        trans = btrfs_start_transaction(root, 1);
-       if (IS_ERR(trans)) {
-               btrfs_free_path(path);
+       if (IS_ERR(trans))
                return PTR_ERR(trans);
-       }
 
        fprintf(stderr, "repairing missing dir index item for inode %llu\n",
                (unsigned long long)rec->ino);
+
+       btrfs_init_path(&path);
        key.objectid = backref->dir;
        key.type = BTRFS_DIR_INDEX_KEY;
        key.offset = backref->index;
-
-       ret = btrfs_insert_empty_item(trans, root, path, &key, data_size);
+       ret = btrfs_insert_empty_item(trans, root, &path, &key, data_size);
        BUG_ON(ret);
 
-       leaf = path->nodes[0];
-       dir_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dir_item);
+       leaf = path.nodes[0];
+       dir_item = btrfs_item_ptr(leaf, path.slots[0], struct btrfs_dir_item);
 
        disk_key.objectid = cpu_to_le64(rec->ino);
        disk_key.type = BTRFS_INODE_ITEM_KEY;
@@ -2126,7 +2226,7 @@ static int add_missing_dir_index(struct btrfs_root *root,
        name_ptr = (unsigned long)(dir_item + 1);
        write_extent_buffer(leaf, backref->name, name_ptr, backref->namelen);
        btrfs_mark_buffer_dirty(leaf);
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        btrfs_commit_transaction(trans, root);
 
        backref->found_dir_index = 1;
@@ -2151,31 +2251,25 @@ static int delete_dir_index(struct btrfs_root *root,
 {
        struct btrfs_trans_handle *trans;
        struct btrfs_dir_item *di;
-       struct btrfs_path *path;
+       struct btrfs_path path;
        int ret = 0;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
        trans = btrfs_start_transaction(root, 1);
-       if (IS_ERR(trans)) {
-               btrfs_free_path(path);
+       if (IS_ERR(trans))
                return PTR_ERR(trans);
-       }
-
 
        fprintf(stderr, "Deleting bad dir index [%llu,%u,%llu] root %llu\n",
                (unsigned long long)backref->dir,
                BTRFS_DIR_INDEX_KEY, (unsigned long long)backref->index,
                (unsigned long long)root->objectid);
 
-       di = btrfs_lookup_dir_index(trans, root, path, backref->dir,
+       btrfs_init_path(&path);
+       di = btrfs_lookup_dir_index(trans, root, &path, backref->dir,
                                    backref->name, backref->namelen,
                                    backref->index, -1);
        if (IS_ERR(di)) {
                ret = PTR_ERR(di);
-               btrfs_free_path(path);
+               btrfs_release_path(&path);
                btrfs_commit_transaction(trans, root);
                if (ret == -ENOENT)
                        return 0;
@@ -2183,11 +2277,11 @@ static int delete_dir_index(struct btrfs_root *root,
        }
 
        if (!di)
-               ret = btrfs_del_item(trans, root, path);
+               ret = btrfs_del_item(trans, root, &path);
        else
-               ret = btrfs_delete_one_dir_name(trans, root, path, di);
+               ret = btrfs_delete_one_dir_name(trans, root, &path, di);
        BUG_ON(ret);
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        btrfs_commit_transaction(trans, root);
        return ret;
 }
@@ -2590,48 +2684,46 @@ out:
  */
 static int find_normal_file_extent(struct btrfs_root *root, u64 ino)
 {
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_file_extent_item *fi;
        u8 type;
        int ret = 0;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               goto out;
+       btrfs_init_path(&path);
        key.objectid = ino;
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = 0;
 
-       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0) {
                ret = 0;
                goto out;
        }
-       if (ret && path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-               ret = btrfs_next_leaf(root, path);
+       if (ret && path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
+               ret = btrfs_next_leaf(root, &path);
                if (ret) {
                        ret = 0;
                        goto out;
                }
        }
        while (1) {
-               btrfs_item_key_to_cpu(path->nodes[0], &found_key,
-                                     path->slots[0]);
+               btrfs_item_key_to_cpu(path.nodes[0], &found_key,
+                                     path.slots[0]);
                if (found_key.objectid != ino ||
                    found_key.type != BTRFS_EXTENT_DATA_KEY)
                        break;
-               fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
+               fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
                                    struct btrfs_file_extent_item);
-               type = btrfs_file_extent_type(path->nodes[0], fi);
+               type = btrfs_file_extent_type(path.nodes[0], fi);
                if (type != BTRFS_FILE_EXTENT_INLINE) {
                        ret = 1;
                        goto out;
                }
        }
 out:
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return ret;
 }
 
@@ -2689,7 +2781,7 @@ static int repair_inode_no_item(struct btrfs_trans_handle *trans,
                        type_recovered = 1;
                        filetype = BTRFS_FT_REG_FILE;
                } else{
-                       printf("Can't determint the filetype for inode %llu, assume it is a normal file\n",
+                       printf("Can't determine the filetype for inode %llu, assume it is a normal file\n",
                               rec->ino);
                        type_recovered = 1;
                        filetype = BTRFS_FT_REG_FILE;
@@ -2822,7 +2914,7 @@ out:
 static int try_repair_inode(struct btrfs_root *root, struct inode_record *rec)
 {
        struct btrfs_trans_handle *trans;
-       struct btrfs_path *path;
+       struct btrfs_path path;
        int ret = 0;
 
        if (!(rec->errors & (I_ERR_DIR_ISIZE_WRONG |
@@ -2834,10 +2926,6 @@ static int try_repair_inode(struct btrfs_root *root, struct inode_record *rec)
                             I_ERR_FILE_NBYTES_WRONG)))
                return rec->errors;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
        /*
         * For nlink repair, it may create a dir and add link, so
         * 2 for parent(256)'s dir_index and dir_item
@@ -2846,27 +2934,26 @@ static int try_repair_inode(struct btrfs_root *root, struct inode_record *rec)
         * 2 for lost+found dir's dir_index and dir_item for the file
         */
        trans = btrfs_start_transaction(root, 7);
-       if (IS_ERR(trans)) {
-               btrfs_free_path(path);
+       if (IS_ERR(trans))
                return PTR_ERR(trans);
-       }
 
+       btrfs_init_path(&path);
        if (rec->errors & I_ERR_NO_INODE_ITEM)
-               ret = repair_inode_no_item(trans, root, path, rec);
+               ret = repair_inode_no_item(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_FILE_EXTENT_ORPHAN)
-               ret = repair_inode_orphan_extent(trans, root, path, rec);
+               ret = repair_inode_orphan_extent(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_FILE_EXTENT_DISCOUNT)
-               ret = repair_inode_discount_extent(trans, root, path, rec);
+               ret = repair_inode_discount_extent(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_DIR_ISIZE_WRONG)
-               ret = repair_inode_isize(trans, root, path, rec);
+               ret = repair_inode_isize(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_NO_ORPHAN_ITEM)
-               ret = repair_inode_orphan_item(trans, root, path, rec);
+               ret = repair_inode_orphan_item(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_LINK_COUNT_WRONG)
-               ret = repair_inode_nlinks(trans, root, path, rec);
+               ret = repair_inode_nlinks(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_FILE_NBYTES_WRONG)
-               ret = repair_inode_nbytes(trans, root, path, rec);
+               ret = repair_inode_nbytes(trans, root, &path, rec);
        btrfs_commit_transaction(trans, root);
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return ret;
 }
 
@@ -2892,7 +2979,7 @@ static int check_inode_recs(struct btrfs_root *root,
        /*
         * We need to record the highest inode number for later 'lost+found'
         * dir creation.
-        * We must select a ino not used/refered by any existing inode, or
+        * We must select an ino not used/referred by any existing inode, or
         * 'lost+found' ino may be a missing ino in a corrupted leaf,
         * this may cause 'lost+found' dir has wrong nlinks.
         */
@@ -3113,13 +3200,12 @@ static void free_root_record(struct cache_extent *cache)
 
        rec = container_of(cache, struct root_record, cache);
        while (!list_empty(&rec->backrefs)) {
-               backref = list_entry(rec->backrefs.next,
-                                    struct root_backref, list);
+               backref = to_root_backref(rec->backrefs.next);
                list_del(&backref->list);
                free(backref);
        }
 
-       kfree(rec);
+       free(rec);
 }
 
 FREE_EXTENT_CACHE_BASED_TREE(root_recs, free_root_record);
@@ -3400,7 +3486,7 @@ static int repair_btree(struct btrfs_root *root,
                        struct cache_tree *corrupt_blocks)
 {
        struct btrfs_trans_handle *trans;
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_corrupt_block *corrupt;
        struct cache_extent *cache;
        struct btrfs_key key;
@@ -3411,23 +3497,20 @@ static int repair_btree(struct btrfs_root *root,
        if (cache_tree_empty(corrupt_blocks))
                return 0;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                fprintf(stderr, "Error starting transaction: %s\n",
                        strerror(-ret));
-               goto out_free_path;
+               return ret;
        }
+       btrfs_init_path(&path);
        cache = first_cache_extent(corrupt_blocks);
        while (cache) {
                corrupt = container_of(cache, struct btrfs_corrupt_block,
                                       cache);
                level = corrupt->level;
-               path->lowest_level = level;
+               path.lowest_level = level;
                key.objectid = corrupt->key.objectid;
                key.type = corrupt->key.type;
                key.offset = corrupt->key.offset;
@@ -3438,22 +3521,22 @@ static int repair_btree(struct btrfs_root *root,
                 * so ins_len set to 0 here.
                 * Balance will be done after all corrupt node/leaf is deleted.
                 */
-               ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+               ret = btrfs_search_slot(trans, root, &key, &path, 0, 1);
                if (ret < 0)
                        goto out;
-               offset = btrfs_node_blockptr(path->nodes[level],
-                                            path->slots[level]);
+               offset = btrfs_node_blockptr(path.nodes[level],
+                                            path.slots[level]);
 
                /* Remove the ptr */
-               ret = btrfs_del_ptr(trans, root, path, level,
-                                   path->slots[level]);
+               ret = btrfs_del_ptr(trans, root, &path, level,
+                                   path.slots[level]);
                if (ret < 0)
                        goto out;
                /*
                 * Remove the corresponding extent
                 * return value is not concerned.
                 */
-               btrfs_release_path(path);
+               btrfs_release_path(&path);
                ret = btrfs_free_extent(trans, root, offset, root->nodesize,
                                        0, root->root_key.objectid,
                                        level - 1, 0);
@@ -3466,18 +3549,17 @@ static int repair_btree(struct btrfs_root *root,
                corrupt = container_of(cache, struct btrfs_corrupt_block,
                                       cache);
                memcpy(&key, &corrupt->key, sizeof(key));
-               ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+               ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
                if (ret < 0)
                        goto out;
                /* return will always >0 since it won't find the item */
                ret = 0;
-               btrfs_release_path(path);
+               btrfs_release_path(&path);
                cache = next_cache_extent(cache);
        }
 out:
        btrfs_commit_transaction(trans, root);
-out_free_path:
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return ret;
 }
 
@@ -3497,6 +3579,7 @@ static int check_fs_root(struct btrfs_root *root,
        struct orphan_data_extent *orphan;
        struct orphan_data_extent *tmp;
        enum btrfs_tree_block_status status;
+       struct node_refs nrefs;
 
        /*
         * Reuse the corrupt_block cache tree to record corrupted tree block
@@ -3518,6 +3601,7 @@ static int check_fs_root(struct btrfs_root *root,
        memset(&root_node, 0, sizeof(root_node));
        cache_tree_init(&root_node.root_cache);
        cache_tree_init(&root_node.inode_cache);
+       memset(&nrefs, 0, sizeof(nrefs));
 
        /* Move the orphan extent record to corresponding inode_record */
        list_for_each_entry_safe(orphan, tmp,
@@ -3557,6 +3641,11 @@ static int check_fs_root(struct btrfs_root *root,
                btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
                level = root_item->drop_level;
                path.lowest_level = level;
+               if (level > btrfs_header_level(root->node) ||
+                   level >= BTRFS_MAX_LEVEL) {
+                       error("ignoring invalid drop level: %u", level);
+                       goto skip_walking;
+               }
                wret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
                if (wret < 0)
                        goto skip_walking;
@@ -3567,7 +3656,7 @@ static int check_fs_root(struct btrfs_root *root,
        }
 
        while (1) {
-               wret = walk_down_tree(root, &path, wc, &level);
+               wret = walk_down_tree(root, &path, wc, &level, &nrefs);
                if (wret < 0)
                        ret = wret;
                if (wret != 0)
        return err;
 }
 
-static int all_backpointers_checked(struct extent_record *rec, int print_errs)
+#define ROOT_DIR_ERROR         (1<<1)  /* bad ROOT_DIR */
+#define DIR_ITEM_MISSING       (1<<2)  /* DIR_ITEM not found */
+#define DIR_ITEM_MISMATCH      (1<<3)  /* DIR_ITEM found but not match */
+#define INODE_REF_MISSING      (1<<4)  /* INODE_REF/INODE_EXTREF not found */
+#define INODE_ITEM_MISSING     (1<<5)  /* INODE_ITEM not found */
+#define INODE_ITEM_MISMATCH    (1<<6)  /* INODE_ITEM found but not match */
+#define FILE_EXTENT_ERROR      (1<<7)  /* bad FILE_EXTENT */
+#define ODD_CSUM_ITEM          (1<<8)  /* CSUM_ITEM error */
+#define CSUM_ITEM_MISSING      (1<<9)  /* CSUM_ITEM not found */
+#define LINK_COUNT_ERROR       (1<<10) /* INODE_ITEM nlink count error */
+#define NBYTES_ERROR           (1<<11) /* INODE_ITEM nbytes count error */
+#define ISIZE_ERROR            (1<<12) /* INODE_ITEM size count error */
+#define ORPHAN_ITEM            (1<<13) /* INODE_ITEM no reference */
+#define NO_INODE_ITEM          (1<<14) /* no inode_item */
+#define LAST_ITEM              (1<<15) /* Complete this tree traversal */
+#define ROOT_REF_MISSING       (1<<16) /* ROOT_REF not found */
+#define ROOT_REF_MISMATCH      (1<<17) /* ROOT_REF found but not match */
+
+/*
+ * Find DIR_ITEM/DIR_INDEX for the given key and check it with the specified
+ * INODE_REF/INODE_EXTREF match.
+ *
+ * @root:      the root of the fs/file tree
+ * @ref_key:   the key of the INODE_REF/INODE_EXTREF
+ * @key:       the key of the DIR_ITEM/DIR_INDEX
+ * @index:     the index in the INODE_REF/INODE_EXTREF, be used to
+ *             distinguish root_dir between normal dir/file
+ * @name:      the name in the INODE_REF/INODE_EXTREF
+ * @namelen:   the length of name in the INODE_REF/INODE_EXTREF
+ * @mode:      the st_mode of INODE_ITEM
+ *
+ * Return 0 if no error occurred.
+ * Return ROOT_DIR_ERROR if found DIR_ITEM/DIR_INDEX for root_dir.
+ * Return DIR_ITEM_MISSING if couldn't find DIR_ITEM/DIR_INDEX for normal
+ * dir/file.
+ * Return DIR_ITEM_MISMATCH if INODE_REF/INODE_EXTREF and DIR_ITEM/DIR_INDEX
+ * not match for normal dir/file.
+ */
+static int find_dir_item(struct btrfs_root *root, struct btrfs_key *ref_key,
+                        struct btrfs_key *key, u64 index, char *name,
+                        u32 namelen, u32 mode)
 {
-       struct list_head *cur = rec->backrefs.next;
-       struct extent_backref *back;
-       struct tree_backref *tback;
-       struct data_backref *dback;
-       u64 found = 0;
-       int err = 0;
+       struct btrfs_path path;
+       struct extent_buffer *node;
+       struct btrfs_dir_item *di;
+       struct btrfs_key location;
+       char namebuf[BTRFS_NAME_LEN] = {0};
+       u32 total;
+       u32 cur = 0;
+       u32 len;
+       u32 name_len;
+       u32 data_len;
+       u8 filetype;
+       int slot;
+       int ret;
 
-       while(cur != &rec->backrefs) {
-               back = list_entry(cur, struct extent_backref, list);
-               cur = cur->next;
-               if (!back->found_extent_tree) {
-                       err = 1;
-                       if (!print_errs)
-                               goto out;
-                       if (back->is_data) {
-                               dback = (struct data_backref *)back;
-                               fprintf(stderr, "Backref %llu %s %llu"
-                                       " owner %llu offset %llu num_refs %lu"
-                                       " not found in extent tree\n",
-                                       (unsigned long long)rec->start,
-                                       back->full_backref ?
-                                       "parent" : "root",
-                                       back->full_backref ?
-                                       (unsigned long long)dback->parent:
-                                       (unsigned long long)dback->root,
-                                       (unsigned long long)dback->owner,
-                                       (unsigned long long)dback->offset,
-                                       (unsigned long)dback->num_refs);
-                       } else {
-                               tback = (struct tree_backref *)back;
-                               fprintf(stderr, "Backref %llu parent %llu"
-                                       " root %llu not found in extent tree\n",
-                                       (unsigned long long)rec->start,
-                                       (unsigned long long)tback->parent,
-                                       (unsigned long long)tback->root);
-                       }
-               }
-               if (!back->is_data && !back->found_ref) {
-                       err = 1;
-                       if (!print_errs)
-                               goto out;
-                       tback = (struct tree_backref *)back;
-                       fprintf(stderr, "Backref %llu %s %llu not referenced back %p\n",
-                               (unsigned long long)rec->start,
-                               back->full_backref ? "parent" : "root",
-                               back->full_backref ?
-                               (unsigned long long)tback->parent :
-                               (unsigned long long)tback->root, back);
-               }
-               if (back->is_data) {
-                       dback = (struct data_backref *)back;
-                       if (dback->found_ref != dback->num_refs) {
-                               err = 1;
-                               if (!print_errs)
-                                       goto out;
-                               fprintf(stderr, "Incorrect local backref count"
-                                       " on %llu %s %llu owner %llu"
-                                       " offset %llu found %u wanted %u back %p\n",
-                                       (unsigned long long)rec->start,
-                                       back->full_backref ?
-                                       "parent" : "root",
-                                       back->full_backref ?
-                                       (unsigned long long)dback->parent:
-                                       (unsigned long long)dback->root,
-                                       (unsigned long long)dback->owner,
-                                       (unsigned long long)dback->offset,
-                                       dback->found_ref, dback->num_refs, back);
-                       }
-                       if (dback->disk_bytenr != rec->start) {
-                               err = 1;
-                               if (!print_errs)
-                                       goto out;
-                               fprintf(stderr, "Backref disk bytenr does not"
-                                       " match extent record, bytenr=%llu, "
-                                       "ref bytenr=%llu\n",
-                                       (unsigned long long)rec->start,
-                                       (unsigned long long)dback->disk_bytenr);
-                       }
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, root, key, &path, 0, 0);
+       if (ret < 0) {
+               ret = DIR_ITEM_MISSING;
+               goto out;
+       }
 
-                       if (dback->bytes != rec->nr) {
-                               err = 1;
-                               if (!print_errs)
-                                       goto out;
-                               fprintf(stderr, "Backref bytes do not match "
-                                       "extent backref, bytenr=%llu, ref "
-                                       "bytes=%llu, backref bytes=%llu\n",
-                                       (unsigned long long)rec->start,
-                                       (unsigned long long)rec->nr,
-                                       (unsigned long long)dback->bytes);
-                       }
-               }
-               if (!back->is_data) {
-                       found += 1;
+       /* Process root dir and goto out*/
+       if (index == 0) {
+               if (ret == 0) {
+                       ret = ROOT_DIR_ERROR;
+                       error(
+                       "root %llu INODE %s[%llu %llu] ROOT_DIR shouldn't have %s",
+                               root->objectid,
+                               ref_key->type == BTRFS_INODE_REF_KEY ?
+                                       "REF" : "EXTREF",
+                               ref_key->objectid, ref_key->offset,
+                               key->type == BTRFS_DIR_ITEM_KEY ?
+                                       "DIR_ITEM" : "DIR_INDEX");
                } else {
-                       dback = (struct data_backref *)back;
-                       found += dback->found_ref;
+                       ret = 0;
                }
+
+               goto out;
        }
-       if (found != rec->refs) {
-               err = 1;
-               if (!print_errs)
-                       goto out;
-               fprintf(stderr, "Incorrect global backref count "
-                       "on %llu found %llu wanted %llu\n",
-                       (unsigned long long)rec->start,
-                       (unsigned long long)found,
-                       (unsigned long long)rec->refs);
+
+       /* Process normal file/dir */
+       if (ret > 0) {
+               ret = DIR_ITEM_MISSING;
+               error(
+               "root %llu INODE %s[%llu %llu] doesn't have related %s[%llu %llu] namelen %u filename %s filetype %d",
+                       root->objectid,
+                       ref_key->type == BTRFS_INODE_REF_KEY ? "REF" : "EXTREF",
+                       ref_key->objectid, ref_key->offset,
+                       key->type == BTRFS_DIR_ITEM_KEY ?
+                               "DIR_ITEM" : "DIR_INDEX",
+                       key->objectid, key->offset, namelen, name,
+                       imode_to_type(mode));
+               goto out;
        }
-out:
-       return err;
-}
 
-static int free_all_extent_backrefs(struct extent_record *rec)
-{
-       struct extent_backref *back;
-       struct list_head *cur;
-       while (!list_empty(&rec->backrefs)) {
-               cur = rec->backrefs.next;
-               back = list_entry(cur, struct extent_backref, list);
-               list_del(cur);
-               free(back);
+       /* Check whether inode_id/filetype/name match */
+       node = path.nodes[0];
+       slot = path.slots[0];
+       di = btrfs_item_ptr(node, slot, struct btrfs_dir_item);
+       total = btrfs_item_size_nr(node, slot);
+       while (cur < total) {
+               ret = DIR_ITEM_MISMATCH;
+               name_len = btrfs_dir_name_len(node, di);
+               data_len = btrfs_dir_data_len(node, di);
+
+               btrfs_dir_item_key_to_cpu(node, di, &location);
+               if (location.objectid != ref_key->objectid ||
+                   location.type !=  BTRFS_INODE_ITEM_KEY ||
+                   location.offset != 0)
+                       goto next;
+
+               filetype = btrfs_dir_type(node, di);
+               if (imode_to_type(mode) != filetype)
+                       goto next;
+
+               if (name_len <= BTRFS_NAME_LEN) {
+                       len = name_len;
+               } else {
+                       len = BTRFS_NAME_LEN;
+                       warning("root %llu %s[%llu %llu] name too long %u, trimmed",
+                       root->objectid,
+                       key->type == BTRFS_DIR_ITEM_KEY ?
+                       "DIR_ITEM" : "DIR_INDEX",
+                       key->objectid, key->offset, name_len);
+               }
+               read_extent_buffer(node, namebuf, (unsigned long)(di + 1), len);
+               if (len != namelen || strncmp(namebuf, name, len))
+                       goto next;
+
+               ret = 0;
+               goto out;
+next:
+               len = sizeof(*di) + name_len + data_len;
+               di = (struct btrfs_dir_item *)((char *)di + len);
+               cur += len;
        }
-       return 0;
+       if (ret == DIR_ITEM_MISMATCH)
+               error(
+               "root %llu INODE %s[%llu %llu] and %s[%llu %llu] mismatch namelen %u filename %s filetype %d",
+                       root->objectid,
+                       ref_key->type == BTRFS_INODE_REF_KEY ? "REF" : "EXTREF",
+                       ref_key->objectid, ref_key->offset,
+                       key->type == BTRFS_DIR_ITEM_KEY ?
+                               "DIR_ITEM" : "DIR_INDEX",
+                       key->objectid, key->offset, namelen, name,
+                       imode_to_type(mode));
+out:
+       btrfs_release_path(&path);
+       return ret;
 }
 
-static void free_extent_record_cache(struct btrfs_fs_info *fs_info,
-                                    struct cache_tree *extent_cache)
+/*
+ * Traverse the given INODE_REF and call find_dir_item() to find related
+ * DIR_ITEM/DIR_INDEX.
+ *
+ * @root:      the root of the fs/file tree
+ * @ref_key:   the key of the INODE_REF
+ * @refs:      the count of INODE_REF
+ * @mode:      the st_mode of INODE_ITEM
+ *
+ * Return 0 if no error occurred.
+ */
+static int check_inode_ref(struct btrfs_root *root, struct btrfs_key *ref_key,
+                          struct extent_buffer *node, int slot, u64 *refs,
+                          int mode)
 {
-       struct cache_extent *cache;
-       struct extent_record *rec;
+       struct btrfs_key key;
+       struct btrfs_inode_ref *ref;
+       char namebuf[BTRFS_NAME_LEN] = {0};
+       u32 total;
+       u32 cur = 0;
+       u32 len;
+       u32 name_len;
+       u64 index;
+       int ret, err = 0;
 
-       while (1) {
-               cache = first_cache_extent(extent_cache);
-               if (!cache)
-                       break;
-               rec = container_of(cache, struct extent_record, cache);
-               remove_cache_extent(extent_cache, cache);
-               free_all_extent_backrefs(rec);
-               free(rec);
+       ref = btrfs_item_ptr(node, slot, struct btrfs_inode_ref);
+       total = btrfs_item_size_nr(node, slot);
+
+next:
+       /* Update inode ref count */
+       (*refs)++;
+
+       index = btrfs_inode_ref_index(node, ref);
+       name_len = btrfs_inode_ref_name_len(node, ref);
+       if (name_len <= BTRFS_NAME_LEN) {
+               len = name_len;
+       } else {
+               len = BTRFS_NAME_LEN;
+               warning("root %llu INODE_REF[%llu %llu] name too long",
+                       root->objectid, ref_key->objectid, ref_key->offset);
        }
-}
 
-static int maybe_free_extent_rec(struct cache_tree *extent_cache,
-                                struct extent_record *rec)
-{
-       if (rec->content_checked && rec->owner_ref_checked &&
-           rec->extent_item_refs == rec->refs && rec->refs > 0 &&
-           rec->num_duplicates == 0 && !all_backpointers_checked(rec, 0) &&
-           !rec->bad_full_backref && !rec->crossing_stripes &&
-           !rec->wrong_chunk_type) {
-               remove_cache_extent(extent_cache, &rec->cache);
-               free_all_extent_backrefs(rec);
-               list_del_init(&rec->list);
-               free(rec);
+       read_extent_buffer(node, namebuf, (unsigned long)(ref + 1), len);
+
+       /* Check root dir ref name */
+       if (index == 0 && strncmp(namebuf, "..", name_len)) {
+               error("root %llu INODE_REF[%llu %llu] ROOT_DIR name shouldn't be %s",
+                     root->objectid, ref_key->objectid, ref_key->offset,
+                     namebuf);
+               err |= ROOT_DIR_ERROR;
        }
-       return 0;
+
+       /* Find related DIR_INDEX */
+       key.objectid = ref_key->offset;
+       key.type = BTRFS_DIR_INDEX_KEY;
+       key.offset = index;
+       ret = find_dir_item(root, ref_key, &key, index, namebuf, len, mode);
+       err |= ret;
+
+       /* Find related dir_item */
+       key.objectid = ref_key->offset;
+       key.type = BTRFS_DIR_ITEM_KEY;
+       key.offset = btrfs_name_hash(namebuf, len);
+       ret = find_dir_item(root, ref_key, &key, index, namebuf, len, mode);
+       err |= ret;
+
+       len = sizeof(*ref) + name_len;
+       ref = (struct btrfs_inode_ref *)((char *)ref + len);
+       cur += len;
+       if (cur < total)
+               goto next;
+
+       return err;
 }
 
-static int check_owner_ref(struct btrfs_root *root,
-                           struct extent_record *rec,
-                           struct extent_buffer *buf)
+/*
+ * Traverse the given INODE_EXTREF and call find_dir_item() to find related
+ * DIR_ITEM/DIR_INDEX.
+ *
+ * @root:      the root of the fs/file tree
+ * @ref_key:   the key of the INODE_EXTREF
+ * @refs:      the count of INODE_EXTREF
+ * @mode:      the st_mode of INODE_ITEM
+ *
+ * Return 0 if no error occurred.
+ */
+static int check_inode_extref(struct btrfs_root *root,
+                             struct btrfs_key *ref_key,
+                             struct extent_buffer *node, int slot, u64 *refs,
+                             int mode)
 {
-       struct extent_backref *node;
-       struct tree_backref *back;
-       struct btrfs_root *ref_root;
        struct btrfs_key key;
-       struct btrfs_path path;
-       struct extent_buffer *parent;
-       int level;
-       int found = 0;
+       struct btrfs_inode_extref *extref;
+       char namebuf[BTRFS_NAME_LEN] = {0};
+       u32 total;
+       u32 cur = 0;
+       u32 len;
+       u32 name_len;
+       u64 index;
+       u64 parent;
        int ret;
+       int err = 0;
 
-       list_for_each_entry(node, &rec->backrefs, list) {
-               if (node->is_data)
-                       continue;
-               if (!node->found_ref)
-                       continue;
-               if (node->full_backref)
-                       continue;
-               back = (struct tree_backref *)node;
-               if (btrfs_header_owner(buf) == back->root)
-                       return 0;
+       extref = btrfs_item_ptr(node, slot, struct btrfs_inode_extref);
+       total = btrfs_item_size_nr(node, slot);
+
+next:
+       /* update inode ref count */
+       (*refs)++;
+       name_len = btrfs_inode_extref_name_len(node, extref);
+       index = btrfs_inode_extref_index(node, extref);
+       parent = btrfs_inode_extref_parent(node, extref);
+       if (name_len <= BTRFS_NAME_LEN) {
+               len = name_len;
+       } else {
+               len = BTRFS_NAME_LEN;
+               warning("root %llu INODE_EXTREF[%llu %llu] name too long",
+                       root->objectid, ref_key->objectid, ref_key->offset);
        }
-       BUG_ON(rec->is_root);
+       read_extent_buffer(node, namebuf, (unsigned long)(extref + 1), len);
 
-       /* try to find the block by search corresponding fs tree */
-       key.objectid = btrfs_header_owner(buf);
-       key.type = BTRFS_ROOT_ITEM_KEY;
-       key.offset = (u64)-1;
+       /* Check root dir ref name */
+       if (index == 0 && strncmp(namebuf, "..", name_len)) {
+               error("root %llu INODE_EXTREF[%llu %llu] ROOT_DIR name shouldn't be %s",
+                     root->objectid, ref_key->objectid, ref_key->offset,
+                     namebuf);
+               err |= ROOT_DIR_ERROR;
+       }
 
-       ref_root = btrfs_read_fs_root(root->fs_info, &key);
-       if (IS_ERR(ref_root))
-               return 1;
+       /* find related dir_index */
+       key.objectid = parent;
+       key.type = BTRFS_DIR_INDEX_KEY;
+       key.offset = index;
+       ret = find_dir_item(root, ref_key, &key, index, namebuf, len, mode);
+       err |= ret;
 
-       level = btrfs_header_level(buf);
-       if (level == 0)
-               btrfs_item_key_to_cpu(buf, &key, 0);
-       else
-               btrfs_node_key_to_cpu(buf, &key, 0);
+       /* find related dir_item */
+       key.objectid = parent;
+       key.type = BTRFS_DIR_ITEM_KEY;
+       key.offset = btrfs_name_hash(namebuf, len);
+       ret = find_dir_item(root, ref_key, &key, index, namebuf, len, mode);
+       err |= ret;
 
-       btrfs_init_path(&path);
-       path.lowest_level = level + 1;
-       ret = btrfs_search_slot(NULL, ref_root, &key, &path, 0, 0);
-       if (ret < 0)
-               return 0;
+       len = sizeof(*extref) + name_len;
+       extref = (struct btrfs_inode_extref *)((char *)extref + len);
+       cur += len;
 
-       parent = path.nodes[level + 1];
-       if (parent && buf->start == btrfs_node_blockptr(parent,
-                                                       path.slots[level + 1]))
-               found = 1;
+       if (cur < total)
+               goto next;
 
-       btrfs_release_path(&path);
-       return found ? 0 : 1;
+       return err;
 }
 
-static int is_extent_tree_record(struct extent_record *rec)
+/*
+ * Find INODE_REF/INODE_EXTREF for the given key and check it with the specified
+ * DIR_ITEM/DIR_INDEX match.
+ *
+ * @root:      the root of the fs/file tree
+ * @key:       the key of the INODE_REF/INODE_EXTREF
+ * @name:      the name in the INODE_REF/INODE_EXTREF
+ * @namelen:   the length of name in the INODE_REF/INODE_EXTREF
+ * @index:     the index in the INODE_REF/INODE_EXTREF, for DIR_ITEM set index
+ * to (u64)-1
+ * @ext_ref:   the EXTENDED_IREF feature
+ *
+ * Return 0 if no error occurred.
+ * Return >0 for error bitmap
+ */
+static int find_inode_ref(struct btrfs_root *root, struct btrfs_key *key,
+                         char *name, int namelen, u64 index,
+                         unsigned int ext_ref)
 {
-       struct list_head *cur = rec->backrefs.next;
-       struct extent_backref *node;
-       struct tree_backref *back;
-       int is_extent = 0;
+       struct btrfs_path path;
+       struct btrfs_inode_ref *ref;
+       struct btrfs_inode_extref *extref;
+       struct extent_buffer *node;
+       char ref_namebuf[BTRFS_NAME_LEN] = {0};
+       u32 total;
+       u32 cur = 0;
+       u32 len;
+       u32 ref_namelen;
+       u64 ref_index;
+       u64 parent;
+       u64 dir_id;
+       int slot;
+       int ret;
 
-       while(cur != &rec->backrefs) {
-               node = list_entry(cur, struct extent_backref, list);
-               cur = cur->next;
-               if (node->is_data)
-                       return 0;
-               back = (struct tree_backref *)node;
-               if (node->full_backref)
-                       return 0;
-               if (back->root == BTRFS_EXTENT_TREE_OBJECTID)
-                       is_extent = 1;
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, root, key, &path, 0, 0);
+       if (ret) {
+               ret = INODE_REF_MISSING;
+               goto extref;
        }
-       return is_extent;
-}
 
+       node = path.nodes[0];
+       slot = path.slots[0];
 
-static int record_bad_block_io(struct btrfs_fs_info *info,
-                              struct cache_tree *extent_cache,
-                              u64 start, u64 len)
-{
-       struct extent_record *rec;
-       struct cache_extent *cache;
-       struct btrfs_key key;
+       ref = btrfs_item_ptr(node, slot, struct btrfs_inode_ref);
+       total = btrfs_item_size_nr(node, slot);
 
-       cache = lookup_cache_extent(extent_cache, start, len);
-       if (!cache)
-               return 0;
+       /* Iterate all entry of INODE_REF */
+       while (cur < total) {
+               ret = INODE_REF_MISSING;
 
-       rec = container_of(cache, struct extent_record, cache);
-       if (!is_extent_tree_record(rec))
-               return 0;
+               ref_namelen = btrfs_inode_ref_name_len(node, ref);
+               ref_index = btrfs_inode_ref_index(node, ref);
+               if (index != (u64)-1 && index != ref_index)
+                       goto next_ref;
 
-       btrfs_disk_key_to_cpu(&key, &rec->parent_key);
-       return btrfs_add_corrupt_extent_record(info, &key, start, len, 0);
-}
+               if (ref_namelen <= BTRFS_NAME_LEN) {
+                       len = ref_namelen;
+               } else {
+                       len = BTRFS_NAME_LEN;
+                       warning("root %llu INODE %s[%llu %llu] name too long",
+                               root->objectid,
+                               key->type == BTRFS_INODE_REF_KEY ?
+                                       "REF" : "EXTREF",
+                               key->objectid, key->offset);
+               }
+               read_extent_buffer(node, ref_namebuf, (unsigned long)(ref + 1),
+                                  len);
 
-static int swap_values(struct btrfs_root *root, struct btrfs_path *path,
-                      struct extent_buffer *buf, int slot)
-{
-       if (btrfs_header_level(buf)) {
-               struct btrfs_key_ptr ptr1, ptr2;
+               if (len != namelen || strncmp(ref_namebuf, name, len))
+                       goto next_ref;
 
-               read_extent_buffer(buf, &ptr1, btrfs_node_key_ptr_offset(slot),
-                                  sizeof(struct btrfs_key_ptr));
-               read_extent_buffer(buf, &ptr2,
-                                  btrfs_node_key_ptr_offset(slot + 1),
-                                  sizeof(struct btrfs_key_ptr));
-               write_extent_buffer(buf, &ptr1,
-                                   btrfs_node_key_ptr_offset(slot + 1),
-                                   sizeof(struct btrfs_key_ptr));
-               write_extent_buffer(buf, &ptr2,
-                                   btrfs_node_key_ptr_offset(slot),
-                                   sizeof(struct btrfs_key_ptr));
-               if (slot == 0) {
-                       struct btrfs_disk_key key;
-                       btrfs_node_key(buf, &key, 0);
-                       btrfs_fixup_low_keys(root, path, &key,
-                                            btrfs_header_level(buf) + 1);
-               }
-       } else {
-               struct btrfs_item *item1, *item2;
-               struct btrfs_key k1, k2;
-               char *item1_data, *item2_data;
-               u32 item1_offset, item2_offset, item1_size, item2_size;
+               ret = 0;
+               goto out;
+next_ref:
+               len = sizeof(*ref) + ref_namelen;
+               ref = (struct btrfs_inode_ref *)((char *)ref + len);
+               cur += len;
+       }
 
-               item1 = btrfs_item_nr(slot);
-               item2 = btrfs_item_nr(slot + 1);
-               btrfs_item_key_to_cpu(buf, &k1, slot);
-               btrfs_item_key_to_cpu(buf, &k2, slot + 1);
-               item1_offset = btrfs_item_offset(buf, item1);
-               item2_offset = btrfs_item_offset(buf, item2);
-               item1_size = btrfs_item_size(buf, item1);
-               item2_size = btrfs_item_size(buf, item2);
+extref:
+       /* Skip if not support EXTENDED_IREF feature */
+       if (!ext_ref)
+               goto out;
 
-               item1_data = malloc(item1_size);
-               if (!item1_data)
-                       return -ENOMEM;
-               item2_data = malloc(item2_size);
-               if (!item2_data) {
-                       free(item1_data);
-                       return -ENOMEM;
-               }
+       btrfs_release_path(&path);
+       btrfs_init_path(&path);
 
-               read_extent_buffer(buf, item1_data, item1_offset, item1_size);
-               read_extent_buffer(buf, item2_data, item2_offset, item2_size);
+       dir_id = key->offset;
+       key->type = BTRFS_INODE_EXTREF_KEY;
+       key->offset = btrfs_extref_hash(dir_id, name, namelen);
 
-               write_extent_buffer(buf, item1_data, item2_offset, item2_size);
-               write_extent_buffer(buf, item2_data, item1_offset, item1_size);
-               free(item1_data);
-               free(item2_data);
+       ret = btrfs_search_slot(NULL, root, key, &path, 0, 0);
+       if (ret) {
+               ret = INODE_REF_MISSING;
+               goto out;
+       }
 
-               btrfs_set_item_offset(buf, item1, item2_offset);
-               btrfs_set_item_offset(buf, item2, item1_offset);
-               btrfs_set_item_size(buf, item1, item2_size);
-               btrfs_set_item_size(buf, item2, item1_size);
+       node = path.nodes[0];
+       slot = path.slots[0];
 
-               path->slots[0] = slot;
-               btrfs_set_item_key_unsafe(root, path, &k2);
-               path->slots[0] = slot + 1;
-               btrfs_set_item_key_unsafe(root, path, &k1);
-       }
-       return 0;
-}
+       extref = btrfs_item_ptr(node, slot, struct btrfs_inode_extref);
+       cur = 0;
+       total = btrfs_item_size_nr(node, slot);
 
-static int fix_key_order(struct btrfs_trans_handle *trans,
-                        struct btrfs_root *root,
-                        struct btrfs_path *path)
-{
-       struct extent_buffer *buf;
-       struct btrfs_key k1, k2;
-       int i;
-       int level = path->lowest_level;
-       int ret = -EIO;
+       /* Iterate all entry of INODE_EXTREF */
+       while (cur < total) {
+               ret = INODE_REF_MISSING;
 
-       buf = path->nodes[level];
-       for (i = 0; i < btrfs_header_nritems(buf) - 1; i++) {
-               if (level) {
-                       btrfs_node_key_to_cpu(buf, &k1, i);
-                       btrfs_node_key_to_cpu(buf, &k2, i + 1);
+               ref_namelen = btrfs_inode_extref_name_len(node, extref);
+               ref_index = btrfs_inode_extref_index(node, extref);
+               parent = btrfs_inode_extref_parent(node, extref);
+               if (index != (u64)-1 && index != ref_index)
+                       goto next_extref;
+
+               if (parent != dir_id)
+                       goto next_extref;
+
+               if (ref_namelen <= BTRFS_NAME_LEN) {
+                       len = ref_namelen;
                } else {
-                       btrfs_item_key_to_cpu(buf, &k1, i);
-                       btrfs_item_key_to_cpu(buf, &k2, i + 1);
+                       len = BTRFS_NAME_LEN;
+                       warning("Warning: root %llu INODE %s[%llu %llu] name too long\n",
+                               root->objectid,
+                               key->type == BTRFS_INODE_REF_KEY ?
+                                       "REF" : "EXTREF",
+                               key->objectid, key->offset);
                }
-               if (btrfs_comp_cpu_keys(&k1, &k2) < 0)
-                       continue;
-               ret = swap_values(root, path, buf, i);
-               if (ret)
-                       break;
-               btrfs_mark_buffer_dirty(buf);
-               i = 0;
+               read_extent_buffer(node, ref_namebuf,
+                                  (unsigned long)(extref + 1), len);
+
+               if (len != namelen || strncmp(ref_namebuf, name, len))
+                       goto next_extref;
+
+               ret = 0;
+               goto out;
+
+next_extref:
+               len = sizeof(*extref) + ref_namelen;
+               extref = (struct btrfs_inode_extref *)((char *)extref + len);
+               cur += len;
+
        }
+out:
+       btrfs_release_path(&path);
        return ret;
 }
 
-static int delete_bogus_item(struct btrfs_trans_handle *trans,
-                            struct btrfs_root *root,
-                            struct btrfs_path *path,
-                            struct extent_buffer *buf, int slot)
+/*
+ * Traverse the given DIR_ITEM/DIR_INDEX and check related INODE_ITEM and
+ * call find_inode_ref() to check related INODE_REF/INODE_EXTREF.
+ *
+ * @root:      the root of the fs/file tree
+ * @key:       the key of the INODE_REF/INODE_EXTREF
+ * @size:      the st_size of the INODE_ITEM
+ * @ext_ref:   the EXTENDED_IREF feature
+ *
+ * Return 0 if no error occurred.
+ */
+static int check_dir_item(struct btrfs_root *root, struct btrfs_key *key,
+                         struct extent_buffer *node, int slot, u64 *size,
+                         unsigned int ext_ref)
 {
-       struct btrfs_key key;
-       int nritems = btrfs_header_nritems(buf);
+       struct btrfs_dir_item *di;
+       struct btrfs_inode_item *ii;
+       struct btrfs_path path;
+       struct btrfs_key location;
+       char namebuf[BTRFS_NAME_LEN] = {0};
+       u32 total;
+       u32 cur = 0;
+       u32 len;
+       u32 name_len;
+       u32 data_len;
+       u8 filetype;
+       u32 mode;
+       u64 index;
+       int ret;
+       int err = 0;
 
-       btrfs_item_key_to_cpu(buf, &key, slot);
+       /*
+        * For DIR_ITEM set index to (u64)-1, so that find_inode_ref
+        * ignore index check.
+        */
+       index = (key->type == BTRFS_DIR_INDEX_KEY) ? key->offset : (u64)-1;
 
-       /* These are all the keys we can deal with missing. */
-       if (key.type != BTRFS_DIR_INDEX_KEY &&
-           key.type != BTRFS_EXTENT_ITEM_KEY &&
-           key.type != BTRFS_METADATA_ITEM_KEY &&
-           key.type != BTRFS_TREE_BLOCK_REF_KEY &&
-           key.type != BTRFS_EXTENT_DATA_REF_KEY)
-               return -1;
+       di = btrfs_item_ptr(node, slot, struct btrfs_dir_item);
+       total = btrfs_item_size_nr(node, slot);
 
-       printf("Deleting bogus item [%llu,%u,%llu] at slot %d on block %llu\n",
-              (unsigned long long)key.objectid, key.type,
-              (unsigned long long)key.offset, slot, buf->start);
-       memmove_extent_buffer(buf, btrfs_item_nr_offset(slot),
-                             btrfs_item_nr_offset(slot + 1),
-                             sizeof(struct btrfs_item) *
-                             (nritems - slot - 1));
-       btrfs_set_header_nritems(buf, nritems - 1);
-       if (slot == 0) {
-               struct btrfs_disk_key disk_key;
+       while (cur < total) {
+               data_len = btrfs_dir_data_len(node, di);
+               if (data_len)
+                       error("root %llu %s[%llu %llu] data_len shouldn't be %u",
+                             root->objectid, key->type == BTRFS_DIR_ITEM_KEY ?
+                             "DIR_ITEM" : "DIR_INDEX",
+                             key->objectid, key->offset, data_len);
+
+               name_len = btrfs_dir_name_len(node, di);
+               if (name_len <= BTRFS_NAME_LEN) {
+                       len = name_len;
+               } else {
+                       len = BTRFS_NAME_LEN;
+                       warning("root %llu %s[%llu %llu] name too long",
+                               root->objectid,
+                               key->type == BTRFS_DIR_ITEM_KEY ?
+                               "DIR_ITEM" : "DIR_INDEX",
+                               key->objectid, key->offset);
+               }
+               (*size) += name_len;
 
-               btrfs_item_key(buf, &disk_key, 0);
-               btrfs_fixup_low_keys(root, path, &disk_key, 1);
+               read_extent_buffer(node, namebuf, (unsigned long)(di + 1), len);
+               filetype = btrfs_dir_type(node, di);
+
+               btrfs_init_path(&path);
+               btrfs_dir_item_key_to_cpu(node, di, &location);
+
+               /* Ignore related ROOT_ITEM check */
+               if (location.type == BTRFS_ROOT_ITEM_KEY)
+                       goto next;
+
+               /* Check relative INODE_ITEM(existence/filetype) */
+               ret = btrfs_search_slot(NULL, root, &location, &path, 0, 0);
+               if (ret) {
+                       err |= INODE_ITEM_MISSING;
+                       error("root %llu %s[%llu %llu] couldn't find relative INODE_ITEM[%llu] namelen %u filename %s filetype %x",
+                             root->objectid, key->type == BTRFS_DIR_ITEM_KEY ?
+                             "DIR_ITEM" : "DIR_INDEX", key->objectid,
+                             key->offset, location.objectid, name_len,
+                             namebuf, filetype);
+                       goto next;
+               }
+
+               ii = btrfs_item_ptr(path.nodes[0], path.slots[0],
+                                   struct btrfs_inode_item);
+               mode = btrfs_inode_mode(path.nodes[0], ii);
+
+               if (imode_to_type(mode) != filetype) {
+                       err |= INODE_ITEM_MISMATCH;
+                       error("root %llu %s[%llu %llu] relative INODE_ITEM filetype mismatch namelen %u filename %s filetype %d",
+                             root->objectid, key->type == BTRFS_DIR_ITEM_KEY ?
+                             "DIR_ITEM" : "DIR_INDEX", key->objectid,
+                             key->offset, name_len, namebuf, filetype);
+               }
+
+               /* Check relative INODE_REF/INODE_EXTREF */
+               location.type = BTRFS_INODE_REF_KEY;
+               location.offset = key->objectid;
+               ret = find_inode_ref(root, &location, namebuf, len,
+                                      index, ext_ref);
+               err |= ret;
+               if (ret & INODE_REF_MISSING)
+                       error("root %llu %s[%llu %llu] relative INODE_REF missing namelen %u filename %s filetype %d",
+                             root->objectid, key->type == BTRFS_DIR_ITEM_KEY ?
+                             "DIR_ITEM" : "DIR_INDEX", key->objectid,
+                             key->offset, name_len, namebuf, filetype);
+
+next:
+               btrfs_release_path(&path);
+               len = sizeof(*di) + name_len + data_len;
+               di = (struct btrfs_dir_item *)((char *)di + len);
+               cur += len;
+
+               if (key->type == BTRFS_DIR_INDEX_KEY && cur < total) {
+                       error("root %llu DIR_INDEX[%llu %llu] should contain only one entry",
+                             root->objectid, key->objectid, key->offset);
+                       break;
+               }
        }
-       btrfs_mark_buffer_dirty(buf);
-       return 0;
+
+       return err;
 }
 
-static int fix_item_offset(struct btrfs_trans_handle *trans,
-                          struct btrfs_root *root,
-                          struct btrfs_path *path)
+/*
+ * Check file extent datasum/hole, update the size of the file extents,
+ * check and update the last offset of the file extent.
+ *
+ * @root:      the root of fs/file tree.
+ * @fkey:      the key of the file extent.
+ * @nodatasum: INODE_NODATASUM feature.
+ * @size:      the sum of all EXTENT_DATA items size for this inode.
+ * @end:       the offset of the last extent.
+ *
+ * Return 0 if no error occurred.
+ */
+static int check_file_extent(struct btrfs_root *root, struct btrfs_key *fkey,
+                            struct extent_buffer *node, int slot,
+                            unsigned int nodatasum, u64 *size, u64 *end)
 {
-       struct extent_buffer *buf;
-       int i;
-       int ret = 0;
+       struct btrfs_file_extent_item *fi;
+       u64 disk_bytenr;
+       u64 disk_num_bytes;
+       u64 extent_num_bytes;
+       u64 found;
+       unsigned int extent_type;
+       unsigned int is_hole;
+       int ret;
+       int err = 0;
 
-       /* We should only get this for leaves */
-       BUG_ON(path->lowest_level);
-       buf = path->nodes[0];
-again:
-       for (i = 0; i < btrfs_header_nritems(buf); i++) {
-               unsigned int shift = 0, offset;
+       fi = btrfs_item_ptr(node, slot, struct btrfs_file_extent_item);
 
-               if (i == 0 && btrfs_item_end_nr(buf, i) !=
-                   BTRFS_LEAF_DATA_SIZE(root)) {
-                       if (btrfs_item_end_nr(buf, i) >
-                           BTRFS_LEAF_DATA_SIZE(root)) {
-                               ret = delete_bogus_item(trans, root, path,
-                                                       buf, i);
-                               if (!ret)
-                                       goto again;
-                               fprintf(stderr, "item is off the end of the "
-                                       "leaf, can't fix\n");
-                               ret = -EIO;
-                               break;
-                       }
-                       shift = BTRFS_LEAF_DATA_SIZE(root) -
-                               btrfs_item_end_nr(buf, i);
-               } else if (i > 0 && btrfs_item_end_nr(buf, i) !=
-                          btrfs_item_offset_nr(buf, i - 1)) {
-                       if (btrfs_item_end_nr(buf, i) >
-                           btrfs_item_offset_nr(buf, i - 1)) {
-                               ret = delete_bogus_item(trans, root, path,
-                                                       buf, i);
-                               if (!ret)
-                                       goto again;
-                               fprintf(stderr, "items overlap, can't fix\n");
-                               ret = -EIO;
-                               break;
-                       }
-                       shift = btrfs_item_offset_nr(buf, i - 1) -
-                               btrfs_item_end_nr(buf, i);
-               }
-               if (!shift)
-                       continue;
+       extent_type = btrfs_file_extent_type(node, fi);
+       /* Skip if file extent is inline */
+       if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+               struct btrfs_item *e = btrfs_item_nr(slot);
+               u32 item_inline_len;
+
+               item_inline_len = btrfs_file_extent_inline_item_len(node, e);
+               extent_num_bytes = btrfs_file_extent_inline_len(node, slot, fi);
+               if (extent_num_bytes == 0 ||
+                   extent_num_bytes != item_inline_len)
+                       err |= FILE_EXTENT_ERROR;
+               *size += extent_num_bytes;
+               return err;
+       }
 
-               printf("Shifting item nr %d by %u bytes in block %llu\n",
-                      i, shift, (unsigned long long)buf->start);
-               offset = btrfs_item_offset_nr(buf, i);
-               memmove_extent_buffer(buf,
-                                     btrfs_leaf_data(buf) + offset + shift,
-                                     btrfs_leaf_data(buf) + offset,
-                                     btrfs_item_size_nr(buf, i));
-               btrfs_set_item_offset(buf, btrfs_item_nr(i),
-                                     offset + shift);
-               btrfs_mark_buffer_dirty(buf);
+       /* Check extent type */
+       if (extent_type != BTRFS_FILE_EXTENT_REG &&
+                       extent_type != BTRFS_FILE_EXTENT_PREALLOC) {
+               err |= FILE_EXTENT_ERROR;
+               error("root %llu EXTENT_DATA[%llu %llu] type bad",
+                     root->objectid, fkey->objectid, fkey->offset);
+               return err;
        }
 
-       /*
-        * We may have moved things, in which case we want to exit so we don't
-        * write those changes out.  Once we have proper abort functionality in
-        * progs this can be changed to something nicer.
-        */
-       BUG_ON(ret);
-       return ret;
+       /* Check REG_EXTENT/PREALLOC_EXTENT */
+       disk_bytenr = btrfs_file_extent_disk_bytenr(node, fi);
+       disk_num_bytes = btrfs_file_extent_disk_num_bytes(node, fi);
+       extent_num_bytes = btrfs_file_extent_num_bytes(node, fi);
+       is_hole = (disk_bytenr == 0) && (disk_num_bytes == 0);
+
+       /* Check EXTENT_DATA datasum */
+       ret = count_csum_range(root, disk_bytenr, disk_num_bytes, &found);
+       if (found > 0 && nodatasum) {
+               err |= ODD_CSUM_ITEM;
+               error("root %llu EXTENT_DATA[%llu %llu] nodatasum shouldn't have datasum",
+                     root->objectid, fkey->objectid, fkey->offset);
+       } else if (extent_type == BTRFS_FILE_EXTENT_REG && !nodatasum &&
+                  !is_hole &&
+                  (ret < 0 || found == 0 || found < disk_num_bytes)) {
+               err |= CSUM_ITEM_MISSING;
+               error("root %llu EXTENT_DATA[%llu %llu] datasum missing",
+                     root->objectid, fkey->objectid, fkey->offset);
+       } else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC && found > 0) {
+               err |= ODD_CSUM_ITEM;
+               error("root %llu EXTENT_DATA[%llu %llu] prealloc shouldn't have datasum",
+                     root->objectid, fkey->objectid, fkey->offset);
+       }
+
+       /* Check EXTENT_DATA hole */
+       if (no_holes && is_hole) {
+               err |= FILE_EXTENT_ERROR;
+               error("root %llu EXTENT_DATA[%llu %llu] shouldn't be hole",
+                     root->objectid, fkey->objectid, fkey->offset);
+       } else if (!no_holes && *end != fkey->offset) {
+               err |= FILE_EXTENT_ERROR;
+               error("root %llu EXTENT_DATA[%llu %llu] interrupt",
+                     root->objectid, fkey->objectid, fkey->offset);
+       }
+
+       *end += extent_num_bytes;
+       if (!is_hole)
+               *size += extent_num_bytes;
+
+       return err;
 }
 
 /*
- * Attempt to fix basic block failures.  If we can't fix it for whatever reason
- * then just return -EIO.
+ * Check INODE_ITEM and related ITEMs (the same inode number)
+ * 1. check link count
+ * 2. check inode ref/extref
+ * 3. check dir item/index
+ *
+ * @ext_ref:   the EXTENDED_IREF feature
+ *
+ * Return 0 if no error occurred.
+ * Return >0 for error or hit the traversal is done(by error bitmap)
  */
-static int try_to_fix_bad_block(struct btrfs_root *root,
-                               struct extent_buffer *buf,
-                               enum btrfs_tree_block_status status)
+static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path,
+                           unsigned int ext_ref)
 {
-       struct btrfs_trans_handle *trans;
-       struct ulist *roots;
-       struct ulist_node *node;
-       struct btrfs_root *search_root;
-       struct btrfs_path *path;
-       struct ulist_iterator iter;
-       struct btrfs_key root_key, key;
+       struct extent_buffer *node;
+       struct btrfs_inode_item *ii;
+       struct btrfs_key key;
+       u64 inode_id;
+       u32 mode;
+       u64 nlink;
+       u64 nbytes;
+       u64 isize;
+       u64 size = 0;
+       u64 refs = 0;
+       u64 extent_end = 0;
+       u64 extent_size = 0;
+       unsigned int dir;
+       unsigned int nodatasum;
+       int slot;
        int ret;
+       int err = 0;
 
-       if (status != BTRFS_TREE_BLOCK_BAD_KEY_ORDER &&
-           status != BTRFS_TREE_BLOCK_INVALID_OFFSETS)
-               return -EIO;
+       node = path->nodes[0];
+       slot = path->slots[0];
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -EIO;
+       btrfs_item_key_to_cpu(node, &key, slot);
+       inode_id = key.objectid;
 
-       ret = btrfs_find_all_roots(NULL, root->fs_info, buf->start,
-                                  0, &roots);
-       if (ret) {
-               btrfs_free_path(path);
-               return -EIO;
+       if (inode_id == BTRFS_ORPHAN_OBJECTID) {
+               ret = btrfs_next_item(root, path);
+               if (ret > 0)
+                       err |= LAST_ITEM;
+               return err;
        }
 
-       ULIST_ITER_INIT(&iter);
-       while ((node = ulist_next(roots, &iter))) {
-               root_key.objectid = node->val;
-               root_key.type = BTRFS_ROOT_ITEM_KEY;
-               root_key.offset = (u64)-1;
+       ii = btrfs_item_ptr(node, slot, struct btrfs_inode_item);
+       isize = btrfs_inode_size(node, ii);
+       nbytes = btrfs_inode_nbytes(node, ii);
+       mode = btrfs_inode_mode(node, ii);
+       dir = imode_to_type(mode) == BTRFS_FT_DIR;
+       nlink = btrfs_inode_nlink(node, ii);
+       nodatasum = btrfs_inode_flags(node, ii) & BTRFS_INODE_NODATASUM;
 
-               search_root = btrfs_read_fs_root(root->fs_info, &root_key);
-               if (IS_ERR(root)) {
-                       ret = -EIO;
-                       break;
+       while (1) {
+               ret = btrfs_next_item(root, path);
+               if (ret < 0) {
+                       /* out will fill 'err' rusing current statistics */
+                       goto out;
+               } else if (ret > 0) {
+                       err |= LAST_ITEM;
+                       goto out;
                }
 
+               node = path->nodes[0];
+               slot = path->slots[0];
+               btrfs_item_key_to_cpu(node, &key, slot);
+               if (key.objectid != inode_id)
+                       goto out;
 
-               trans = btrfs_start_transaction(search_root, 0);
-               if (IS_ERR(trans)) {
-                       ret = PTR_ERR(trans);
+               switch (key.type) {
+               case BTRFS_INODE_REF_KEY:
+                       ret = check_inode_ref(root, &key, node, slot, &refs,
+                                             mode);
+                       err |= ret;
                        break;
-               }
-
-               path->lowest_level = btrfs_header_level(buf);
-               path->skip_check_block = 1;
-               if (path->lowest_level)
-                       btrfs_node_key_to_cpu(buf, &key, 0);
-               else
-                       btrfs_item_key_to_cpu(buf, &key, 0);
-               ret = btrfs_search_slot(trans, search_root, &key, path, 0, 1);
-               if (ret) {
-                       ret = -EIO;
-                       btrfs_commit_transaction(trans, search_root);
+               case BTRFS_INODE_EXTREF_KEY:
+                       if (key.type == BTRFS_INODE_EXTREF_KEY && !ext_ref)
+                               warning("root %llu EXTREF[%llu %llu] isn't supported",
+                                       root->objectid, key.objectid,
+                                       key.offset);
+                       ret = check_inode_extref(root, &key, node, slot, &refs,
+                                                mode);
+                       err |= ret;
                        break;
-               }
-               if (status == BTRFS_TREE_BLOCK_BAD_KEY_ORDER)
-                       ret = fix_key_order(trans, search_root, path);
-               else if (status == BTRFS_TREE_BLOCK_INVALID_OFFSETS)
-                       ret = fix_item_offset(trans, search_root, path);
-               if (ret) {
-                       btrfs_commit_transaction(trans, search_root);
+               case BTRFS_DIR_ITEM_KEY:
+               case BTRFS_DIR_INDEX_KEY:
+                       if (!dir) {
+                               warning("root %llu INODE[%llu] mode %u shouldn't have DIR_INDEX[%llu %llu]",
+                                       root->objectid, inode_id,
+                                       imode_to_type(mode), key.objectid,
+                                       key.offset);
+                       }
+                       ret = check_dir_item(root, &key, node, slot, &size,
+                                            ext_ref);
+                       err |= ret;
+                       break;
+               case BTRFS_EXTENT_DATA_KEY:
+                       if (dir) {
+                               warning("root %llu DIR INODE[%llu] shouldn't EXTENT_DATA[%llu %llu]",
+                                       root->objectid, inode_id, key.objectid,
+                                       key.offset);
+                       }
+                       ret = check_file_extent(root, &key, node, slot,
+                                               nodatasum, &extent_size,
+                                               &extent_end);
+                       err |= ret;
+                       break;
+               case BTRFS_XATTR_ITEM_KEY:
                        break;
+               default:
+                       error("ITEM[%llu %u %llu] UNKNOWN TYPE",
+                             key.objectid, key.type, key.offset);
                }
-               btrfs_release_path(path);
-               btrfs_commit_transaction(trans, search_root);
        }
-       ulist_free(roots);
-       btrfs_free_path(path);
-       return ret;
-}
-
-static int check_block(struct btrfs_root *root,
-                      struct cache_tree *extent_cache,
-                      struct extent_buffer *buf, u64 flags)
-{
-       struct extent_record *rec;
-       struct cache_extent *cache;
-       struct btrfs_key key;
-       enum btrfs_tree_block_status status;
-       int ret = 0;
-       int level;
-
-       cache = lookup_cache_extent(extent_cache, buf->start, buf->len);
-       if (!cache)
-               return 1;
-       rec = container_of(cache, struct extent_record, cache);
-       rec->generation = btrfs_header_generation(buf);
-
-       level = btrfs_header_level(buf);
-       if (btrfs_header_nritems(buf) > 0) {
-
-               if (level == 0)
-                       btrfs_item_key_to_cpu(buf, &key, 0);
-               else
-                       btrfs_node_key_to_cpu(buf, &key, 0);
 
-               rec->info_objectid = key.objectid;
-       }
-       rec->info_level = level;
+out:
+       /* verify INODE_ITEM nlink/isize/nbytes */
+       if (dir) {
+               if (nlink != 1) {
+                       err |= LINK_COUNT_ERROR;
+                       error("root %llu DIR INODE[%llu] shouldn't have more than one link(%llu)",
+                             root->objectid, inode_id, nlink);
+               }
 
-       if (btrfs_is_leaf(buf))
-               status = btrfs_check_leaf(root, &rec->parent_key, buf);
-       else
-               status = btrfs_check_node(root, &rec->parent_key, buf);
+               /*
+                * Just a warning, as dir inode nbytes is just an
+                * instructive value.
+                */
+               if (!IS_ALIGNED(nbytes, root->nodesize)) {
+                       warning("root %llu DIR INODE[%llu] nbytes should be aligned to %u",
+                               root->objectid, inode_id, root->nodesize);
+               }
 
-       if (status != BTRFS_TREE_BLOCK_CLEAN) {
-               if (repair)
-                       status = try_to_fix_bad_block(root, buf, status);
-               if (status != BTRFS_TREE_BLOCK_CLEAN) {
-                       ret = -EIO;
-                       fprintf(stderr, "bad block %llu\n",
-                               (unsigned long long)buf->start);
-               } else {
-                       /*
-                        * Signal to callers we need to start the scan over
-                        * again since we'll have cow'ed blocks.
-                        */
-                       ret = -EAGAIN;
+               if (isize != size) {
+                       err |= ISIZE_ERROR;
+                       error("root %llu DIR INODE [%llu] size(%llu) not equal to %llu",
+                             root->objectid, inode_id, isize, size);
                }
        } else {
-               rec->content_checked = 1;
-               if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
-                       rec->owner_ref_checked = 1;
-               else {
-                       ret = check_owner_ref(root, rec, buf);
-                       if (!ret)
-                               rec->owner_ref_checked = 1;
+               if (nlink != refs) {
+                       err |= LINK_COUNT_ERROR;
+                       error("root %llu INODE[%llu] nlink(%llu) not equal to inode_refs(%llu)",
+                             root->objectid, inode_id, nlink, refs);
+               } else if (!nlink) {
+                       err |= ORPHAN_ITEM;
                }
-       }
-       if (!ret)
-               maybe_free_extent_rec(extent_cache, rec);
-       return ret;
-}
 
-static struct tree_backref *find_tree_backref(struct extent_record *rec,
-                                               u64 parent, u64 root)
-{
-       struct list_head *cur = rec->backrefs.next;
-       struct extent_backref *node;
-       struct tree_backref *back;
+               if (!nbytes && !no_holes && extent_end < isize) {
+                       err |= NBYTES_ERROR;
+                       error("root %llu INODE[%llu] size (%llu) should have a file extent hole",
+                             root->objectid, inode_id, isize);
+               }
 
-       while(cur != &rec->backrefs) {
-               node = list_entry(cur, struct extent_backref, list);
-               cur = cur->next;
-               if (node->is_data)
-                       continue;
-               back = (struct tree_backref *)node;
-               if (parent > 0) {
-                       if (!node->full_backref)
-                               continue;
-                       if (parent == back->parent)
-                               return back;
-               } else {
-                       if (node->full_backref)
-                               continue;
-                       if (back->root == root)
-                               return back;
+               if (nbytes != extent_size) {
+                       err |= NBYTES_ERROR;
+                       error("root %llu INODE[%llu] nbytes(%llu) not equal to extent_size(%llu)",
+                             root->objectid, inode_id, nbytes, extent_size);
                }
        }
-       return NULL;
+
+       return err;
 }
 
-static struct tree_backref *alloc_tree_backref(struct extent_record *rec,
-                                               u64 parent, u64 root)
+/*
+ * Iterate all item on the tree and call check_inode_item() to check.
+ *
+ * @root:      the root of the tree to be checked.
+ * @ext_ref:   the EXTENDED_IREF feature
+ *
+ * Return 0 if no error found.
+ * Return <0 for error.
+ * All internal error bitmap will be converted to -EIO, to avoid
+ * mixing negative and postive return value.
+ */
+static int check_fs_root_v2(struct btrfs_root *root, unsigned int ext_ref)
 {
-       struct tree_backref *ref = malloc(sizeof(*ref));
+       struct btrfs_path *path;
+       struct btrfs_key key;
+       u64 inode_id;
+       int ret, err = 0;
 
-       if (!ref)
-               return NULL;
-       memset(&ref->node, 0, sizeof(ref->node));
-       if (parent > 0) {
-               ref->parent = parent;
-               ref->node.full_backref = 1;
-       } else {
-               ref->root = root;
-               ref->node.full_backref = 0;
-       }
-       list_add_tail(&ref->node.list, &rec->backrefs);
+       path = btrfs_alloc_path();
+       if (!path)
+               return -ENOMEM;
 
-       return ref;
-}
+       key.objectid = 0;
+       key.type = 0;
+       key.offset = 0;
 
-static struct data_backref *find_data_backref(struct extent_record *rec,
-                                               u64 parent, u64 root,
-                                               u64 owner, u64 offset,
-                                               int found_ref,
-                                               u64 disk_bytenr, u64 bytes)
-{
-       struct list_head *cur = rec->backrefs.next;
-       struct extent_backref *node;
-       struct data_backref *back;
+       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       if (ret < 0)
+               goto out;
 
-       while(cur != &rec->backrefs) {
-               node = list_entry(cur, struct extent_backref, list);
-               cur = cur->next;
-               if (!node->is_data)
+       while (1) {
+               btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+
+               /*
+                * All check must start with inode item, skip if not
+                */
+               if (key.type == BTRFS_INODE_ITEM_KEY) {
+                       ret = check_inode_item(root, path, ext_ref);
+                       err |= ret;
+                       if (err & LAST_ITEM)
+                               goto out;
                        continue;
-               back = (struct data_backref *)node;
-               if (parent > 0) {
-                       if (!node->full_backref)
-                               continue;
-                       if (parent == back->parent)
-                               return back;
-               } else {
-                       if (node->full_backref)
-                               continue;
-                       if (back->root == root && back->owner == owner &&
-                           back->offset == offset) {
-                               if (found_ref && node->found_ref &&
-                                   (back->bytes != bytes ||
-                                   back->disk_bytenr != disk_bytenr))
-                                       continue;
-                               return back;
-                       }
                }
+               error("root %llu ITEM[%llu %u %llu] isn't INODE_ITEM, skip to next inode",
+                     root->objectid, key.objectid, key.type,
+                     key.offset);
+
+               err |= NO_INODE_ITEM;
+               inode_id = key.objectid;
+
+               /*
+                * skip to next inode
+                * TODO: Maybe search_slot() will be faster?
+                */
+               do {
+                       ret = btrfs_next_item(root, path);
+                       if (ret > 0) {
+                               goto out;
+                       } else if (ret < 0) {
+                               err = ret;
+                               goto out;
+                       }
+                       btrfs_item_key_to_cpu(path->nodes[0], &key,
+                                             path->slots[0]);
+               } while (inode_id == key.objectid);
        }
-       return NULL;
+
+out:
+       err &= ~LAST_ITEM;
+       if (err && !ret)
+               ret = -EIO;
+       btrfs_free_path(path);
+       return ret;
 }
 
-static struct data_backref *alloc_data_backref(struct extent_record *rec,
-                                               u64 parent, u64 root,
-                                               u64 owner, u64 offset,
-                                               u64 max_size)
+/*
+ * Find the relative ref for root_ref and root_backref.
+ *
+ * @root:      the root of the root tree.
+ * @ref_key:   the key of the root ref.
+ *
+ * Return 0 if no error occurred.
+ */
+static int check_root_ref(struct btrfs_root *root, struct btrfs_key *ref_key,
+                         struct extent_buffer *node, int slot)
 {
-       struct data_backref *ref = malloc(sizeof(*ref));
+       struct btrfs_path *path;
+       struct btrfs_key key;
+       struct btrfs_root_ref *ref;
+       struct btrfs_root_ref *backref;
+       char ref_name[BTRFS_NAME_LEN] = {0};
+       char backref_name[BTRFS_NAME_LEN] = {0};
+       u64 ref_dirid;
+       u64 ref_seq;
+       u32 ref_namelen;
+       u64 backref_dirid;
+       u64 backref_seq;
+       u32 backref_namelen;
+       u32 len;
+       int ret;
+       int err = 0;
 
-       if (!ref)
-               return NULL;
-       memset(&ref->node, 0, sizeof(ref->node));
-       ref->node.is_data = 1;
+       ref = btrfs_item_ptr(node, slot, struct btrfs_root_ref);
+       ref_dirid = btrfs_root_ref_dirid(node, ref);
+       ref_seq = btrfs_root_ref_sequence(node, ref);
+       ref_namelen = btrfs_root_ref_name_len(node, ref);
 
-       if (parent > 0) {
-               ref->parent = parent;
-               ref->owner = 0;
-               ref->offset = 0;
-               ref->node.full_backref = 1;
+       if (ref_namelen <= BTRFS_NAME_LEN) {
+               len = ref_namelen;
        } else {
-               ref->root = root;
-               ref->owner = owner;
-               ref->offset = offset;
-               ref->node.full_backref = 0;
+               len = BTRFS_NAME_LEN;
+               warning("%s[%llu %llu] ref_name too long",
+                       ref_key->type == BTRFS_ROOT_REF_KEY ?
+                       "ROOT_REF" : "ROOT_BACKREF", ref_key->objectid,
+                       ref_key->offset);
        }
-       ref->bytes = max_size;
-       ref->found_ref = 0;
-       ref->num_refs = 0;
-       list_add_tail(&ref->node.list, &rec->backrefs);
-       if (max_size > rec->max_size)
-               rec->max_size = max_size;
-       return ref;
-}
-
-/* Check if the type of extent matches with its chunk */
-static void check_extent_type(struct extent_record *rec)
-{
-       struct btrfs_block_group_cache *bg_cache;
+       read_extent_buffer(node, ref_name, (unsigned long)(ref + 1), len);
 
-       bg_cache = btrfs_lookup_first_block_group(global_info, rec->start);
-       if (!bg_cache)
-               return;
+       /* Find relative root_ref */
+       key.objectid = ref_key->offset;
+       key.type = BTRFS_ROOT_BACKREF_KEY + BTRFS_ROOT_REF_KEY - ref_key->type;
+       key.offset = ref_key->objectid;
 
-       /* data extent, check chunk directly*/
-       if (!rec->metadata) {
-               if (!(bg_cache->flags & BTRFS_BLOCK_GROUP_DATA))
-                       rec->wrong_chunk_type = 1;
-               return;
+       path = btrfs_alloc_path();
+       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       if (ret) {
+               err |= ROOT_REF_MISSING;
+               error("%s[%llu %llu] couldn't find relative ref",
+                     ref_key->type == BTRFS_ROOT_REF_KEY ?
+                     "ROOT_REF" : "ROOT_BACKREF",
+                     ref_key->objectid, ref_key->offset);
+               goto out;
        }
 
-       /* metadata extent, check the obvious case first */
-       if (!(bg_cache->flags & (BTRFS_BLOCK_GROUP_SYSTEM |
-                                BTRFS_BLOCK_GROUP_METADATA))) {
-               rec->wrong_chunk_type = 1;
-               return;
+       backref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                struct btrfs_root_ref);
+       backref_dirid = btrfs_root_ref_dirid(path->nodes[0], backref);
+       backref_seq = btrfs_root_ref_sequence(path->nodes[0], backref);
+       backref_namelen = btrfs_root_ref_name_len(path->nodes[0], backref);
+
+       if (backref_namelen <= BTRFS_NAME_LEN) {
+               len = backref_namelen;
+       } else {
+               len = BTRFS_NAME_LEN;
+               warning("%s[%llu %llu] ref_name too long",
+                       key.type == BTRFS_ROOT_REF_KEY ?
+                       "ROOT_REF" : "ROOT_BACKREF",
+                       key.objectid, key.offset);
+       }
+       read_extent_buffer(path->nodes[0], backref_name,
+                          (unsigned long)(backref + 1), len);
+
+       if (ref_dirid != backref_dirid || ref_seq != backref_seq ||
+           ref_namelen != backref_namelen ||
+           strncmp(ref_name, backref_name, len)) {
+               err |= ROOT_REF_MISMATCH;
+               error("%s[%llu %llu] mismatch relative ref",
+                     ref_key->type == BTRFS_ROOT_REF_KEY ?
+                     "ROOT_REF" : "ROOT_BACKREF",
+                     ref_key->objectid, ref_key->offset);
        }
+out:
+       btrfs_free_path(path);
+       return err;
+}
 
-       /*
-        * Check SYSTEM extent, as it's also marked as metadata, we can only
-        * make sure it's a SYSTEM extent by its backref
-        */
-       if (!list_empty(&rec->backrefs)) {
-               struct extent_backref *node;
-               struct tree_backref *tback;
-               u64 bg_type;
-
-               node = list_entry(rec->backrefs.next, struct extent_backref,
-                                 list);
-               if (node->is_data) {
-                       /* tree block shouldn't have data backref */
-                       rec->wrong_chunk_type = 1;
-                       return;
-               }
-               tback = container_of(node, struct tree_backref, node);
-
-               if (tback->root == BTRFS_CHUNK_TREE_OBJECTID)
-                       bg_type = BTRFS_BLOCK_GROUP_SYSTEM;
-               else
-                       bg_type = BTRFS_BLOCK_GROUP_METADATA;
-               if (!(bg_cache->flags & bg_type))
-                       rec->wrong_chunk_type = 1;
-       }
-}
-
-static int add_extent_rec_nolookup(struct cache_tree *extent_cache,
-                         struct btrfs_key *parent_key, u64 parent_gen,
-                         u64 start, u64 nr, u64 extent_item_refs,
-                         int is_root, int inc_ref, int set_checked,
-                         int metadata, int extent_rec, u64 max_size)
+/*
+ * Check all fs/file tree in low_memory mode.
+ *
+ * 1. for fs tree root item, call check_fs_root_v2()
+ * 2. for fs tree root ref/backref, call check_root_ref()
+ *
+ * Return 0 if no error occurred.
+ */
+static int check_fs_roots_v2(struct btrfs_fs_info *fs_info)
 {
-       struct extent_record *rec;
-       int ret = 0;
+       struct btrfs_root *tree_root = fs_info->tree_root;
+       struct btrfs_root *cur_root = NULL;
+       struct btrfs_path *path;
+       struct btrfs_key key;
+       struct extent_buffer *node;
+       unsigned int ext_ref;
+       int slot;
+       int ret;
+       int err = 0;
 
-       rec = malloc(sizeof(*rec));
-       if (!rec)
+       ext_ref = btrfs_fs_incompat(fs_info,
+                                   BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF);
+
+       path = btrfs_alloc_path();
+       if (!path)
                return -ENOMEM;
-       rec->start = start;
-       rec->max_size = max_size;
-       rec->nr = max(nr, max_size);
-       rec->found_rec = !!extent_rec;
-       rec->content_checked = 0;
-       rec->owner_ref_checked = 0;
-       rec->num_duplicates = 0;
-       rec->metadata = metadata;
-       rec->flag_block_full_backref = -1;
-       rec->bad_full_backref = 0;
-       rec->crossing_stripes = 0;
-       rec->wrong_chunk_type = 0;
-       INIT_LIST_HEAD(&rec->backrefs);
-       INIT_LIST_HEAD(&rec->dups);
-       INIT_LIST_HEAD(&rec->list);
 
-       if (is_root)
-               rec->is_root = 1;
-       else
-               rec->is_root = 0;
+       key.objectid = BTRFS_FS_TREE_OBJECTID;
+       key.offset = 0;
+       key.type = BTRFS_ROOT_ITEM_KEY;
 
-       if (inc_ref)
-               rec->refs = 1;
-       else
-               rec->refs = 0;
+       ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
+       if (ret < 0) {
+               err = ret;
+               goto out;
+       } else if (ret > 0) {
+               err = -ENOENT;
+               goto out;
+       }
 
-       if (extent_item_refs)
-               rec->extent_item_refs = extent_item_refs;
-       else
-               rec->extent_item_refs = 0;
+       while (1) {
+               node = path->nodes[0];
+               slot = path->slots[0];
+               btrfs_item_key_to_cpu(node, &key, slot);
+               if (key.objectid > BTRFS_LAST_FREE_OBJECTID)
+                       goto out;
+               if (key.type == BTRFS_ROOT_ITEM_KEY &&
+                   fs_root_objectid(key.objectid)) {
+                       if (key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
+                               cur_root = btrfs_read_fs_root_no_cache(fs_info,
+                                                                      &key);
+                       } else {
+                               key.offset = (u64)-1;
+                               cur_root = btrfs_read_fs_root(fs_info, &key);
+                       }
 
-       if (parent_key)
-               btrfs_cpu_key_to_disk(&rec->parent_key, parent_key);
-       else
-               memset(&rec->parent_key, 0, sizeof(*parent_key));
+                       if (IS_ERR(cur_root)) {
+                               error("Fail to read fs/subvol tree: %lld",
+                                     key.objectid);
+                               err = -EIO;
+                               goto next;
+                       }
 
-       if (parent_gen)
-               rec->parent_generation = parent_gen;
-       else
-               rec->parent_generation = 0;
+                       ret = check_fs_root_v2(cur_root, ext_ref);
+                       err |= ret;
 
-       rec->cache.start = start;
-       rec->cache.size = nr;
-       ret = insert_cache_extent(extent_cache, &rec->cache);
-       BUG_ON(ret);
-       bytes_used += nr;
-       if (set_checked) {
-               rec->content_checked = 1;
-               rec->owner_ref_checked = 1;
+                       if (key.objectid == BTRFS_TREE_RELOC_OBJECTID)
+                               btrfs_free_fs_root(cur_root);
+               } else if (key.type == BTRFS_ROOT_REF_KEY ||
+                               key.type == BTRFS_ROOT_BACKREF_KEY) {
+                       ret = check_root_ref(tree_root, &key, node, slot);
+                       err |= ret;
+               }
+next:
+               ret = btrfs_next_item(tree_root, path);
+               if (ret > 0)
+                       goto out;
+               if (ret < 0) {
+                       err = ret;
+                       goto out;
+               }
        }
 
-       if (metadata)
-               rec->crossing_stripes = check_crossing_stripes(rec->start,
-                               rec->max_size);
-       check_extent_type(rec);
-       return ret;
+out:
+       btrfs_free_path(path);
+       return err;
 }
 
-static int add_extent_rec(struct cache_tree *extent_cache,
-                         struct btrfs_key *parent_key, u64 parent_gen,
-                         u64 start, u64 nr, u64 extent_item_refs,
-                         int is_root, int inc_ref, int set_checked,
-                         int metadata, int extent_rec, u64 max_size)
+static int all_backpointers_checked(struct extent_record *rec, int print_errs)
 {
-       struct extent_record *rec;
-       struct cache_extent *cache;
-       int ret = 0;
-       int dup = 0;
-
-       cache = lookup_cache_extent(extent_cache, start, nr);
-       if (cache) {
-               rec = container_of(cache, struct extent_record, cache);
-               if (inc_ref)
-                       rec->refs++;
-               if (rec->nr == 1)
-                       rec->nr = max(nr, max_size);
-
-               /*
-                * We need to make sure to reset nr to whatever the extent
-                * record says was the real size, this way we can compare it to
-                * the backrefs.
-                */
-               if (extent_rec) {
-                       if (start != rec->start || rec->found_rec) {
-                               struct extent_record *tmp;
-
-                               dup = 1;
-                               if (list_empty(&rec->list))
-                                       list_add_tail(&rec->list,
-                                                     &duplicate_extents);
+       struct list_head *cur = rec->backrefs.next;
+       struct extent_backref *back;
+       struct tree_backref *tback;
+       struct data_backref *dback;
+       u64 found = 0;
+       int err = 0;
 
-                               /*
-                                * We have to do this song and dance in case we
-                                * find an extent record that falls inside of
-                                * our current extent record but does not have
-                                * the same objectid.
-                                */
-                               tmp = malloc(sizeof(*tmp));
-                               if (!tmp)
-                                       return -ENOMEM;
-                               tmp->start = start;
-                               tmp->max_size = max_size;
-                               tmp->nr = nr;
-                               tmp->found_rec = 1;
-                               tmp->metadata = metadata;
-                               tmp->extent_item_refs = extent_item_refs;
-                               INIT_LIST_HEAD(&tmp->list);
-                               list_add_tail(&tmp->list, &rec->dups);
-                               rec->num_duplicates++;
+       while(cur != &rec->backrefs) {
+               back = to_extent_backref(cur);
+               cur = cur->next;
+               if (!back->found_extent_tree) {
+                       err = 1;
+                       if (!print_errs)
+                               goto out;
+                       if (back->is_data) {
+                               dback = to_data_backref(back);
+                               fprintf(stderr, "Backref %llu %s %llu"
+                                       " owner %llu offset %llu num_refs %lu"
+                                       " not found in extent tree\n",
+                                       (unsigned long long)rec->start,
+                                       back->full_backref ?
+                                       "parent" : "root",
+                                       back->full_backref ?
+                                       (unsigned long long)dback->parent:
+                                       (unsigned long long)dback->root,
+                                       (unsigned long long)dback->owner,
+                                       (unsigned long long)dback->offset,
+                                       (unsigned long)dback->num_refs);
                        } else {
-                               rec->nr = nr;
-                               rec->found_rec = 1;
+                               tback = to_tree_backref(back);
+                               fprintf(stderr, "Backref %llu parent %llu"
+                                       " root %llu not found in extent tree\n",
+                                       (unsigned long long)rec->start,
+                                       (unsigned long long)tback->parent,
+                                       (unsigned long long)tback->root);
                        }
                }
+               if (!back->is_data && !back->found_ref) {
+                       err = 1;
+                       if (!print_errs)
+                               goto out;
+                       tback = to_tree_backref(back);
+                       fprintf(stderr, "Backref %llu %s %llu not referenced back %p\n",
+                               (unsigned long long)rec->start,
+                               back->full_backref ? "parent" : "root",
+                               back->full_backref ?
+                               (unsigned long long)tback->parent :
+                               (unsigned long long)tback->root, back);
+               }
+               if (back->is_data) {
+                       dback = to_data_backref(back);
+                       if (dback->found_ref != dback->num_refs) {
+                               err = 1;
+                               if (!print_errs)
+                                       goto out;
+                               fprintf(stderr, "Incorrect local backref count"
+                                       " on %llu %s %llu owner %llu"
+                                       " offset %llu found %u wanted %u back %p\n",
+                                       (unsigned long long)rec->start,
+                                       back->full_backref ?
+                                       "parent" : "root",
+                                       back->full_backref ?
+                                       (unsigned long long)dback->parent:
+                                       (unsigned long long)dback->root,
+                                       (unsigned long long)dback->owner,
+                                       (unsigned long long)dback->offset,
+                                       dback->found_ref, dback->num_refs, back);
+                       }
+                       if (dback->disk_bytenr != rec->start) {
+                               err = 1;
+                               if (!print_errs)
+                                       goto out;
+                               fprintf(stderr, "Backref disk bytenr does not"
+                                       " match extent record, bytenr=%llu, "
+                                       "ref bytenr=%llu\n",
+                                       (unsigned long long)rec->start,
+                                       (unsigned long long)dback->disk_bytenr);
+                       }
 
-               if (extent_item_refs && !dup) {
-                       if (rec->extent_item_refs) {
-                               fprintf(stderr, "block %llu rec "
-                                       "extent_item_refs %llu, passed %llu\n",
-                                       (unsigned long long)start,
-                                       (unsigned long long)
-                                                       rec->extent_item_refs,
-                                       (unsigned long long)extent_item_refs);
+                       if (dback->bytes != rec->nr) {
+                               err = 1;
+                               if (!print_errs)
+                                       goto out;
+                               fprintf(stderr, "Backref bytes do not match "
+                                       "extent backref, bytenr=%llu, ref "
+                                       "bytes=%llu, backref bytes=%llu\n",
+                                       (unsigned long long)rec->start,
+                                       (unsigned long long)rec->nr,
+                                       (unsigned long long)dback->bytes);
                        }
-                       rec->extent_item_refs = extent_item_refs;
                }
-               if (is_root)
-                       rec->is_root = 1;
-               if (set_checked) {
-                       rec->content_checked = 1;
-                       rec->owner_ref_checked = 1;
+               if (!back->is_data) {
+                       found += 1;
+               } else {
+                       dback = to_data_backref(back);
+                       found += dback->found_ref;
                }
-
-               if (parent_key)
-                       btrfs_cpu_key_to_disk(&rec->parent_key, parent_key);
-               if (parent_gen)
-                       rec->parent_generation = parent_gen;
-
-               if (rec->max_size < max_size)
-                       rec->max_size = max_size;
-
-               /*
-                * A metadata extent can't cross stripe_len boundary, otherwise
-                * kernel scrub won't be able to handle it.
-                * As now stripe_len is fixed to BTRFS_STRIPE_LEN, just check
-                * it.
-                */
-               if (metadata)
-                       rec->crossing_stripes = check_crossing_stripes(
-                                       rec->start, rec->max_size);
-               check_extent_type(rec);
-               maybe_free_extent_rec(extent_cache, rec);
-               return ret;
        }
+       if (found != rec->refs) {
+               err = 1;
+               if (!print_errs)
+                       goto out;
+               fprintf(stderr, "Incorrect global backref count "
+                       "on %llu found %llu wanted %llu\n",
+                       (unsigned long long)rec->start,
+                       (unsigned long long)found,
+                       (unsigned long long)rec->refs);
+       }
+out:
+       return err;
+}
 
-       ret = add_extent_rec_nolookup(extent_cache, parent_key, parent_gen,
-                       start, nr, extent_item_refs, is_root, inc_ref,
-                       set_checked, metadata, extent_rec, max_size);
-
-       return ret;
-}
-
-static int add_tree_backref(struct cache_tree *extent_cache, u64 bytenr,
-                           u64 parent, u64 root, int found_ref)
+static int free_all_extent_backrefs(struct extent_record *rec)
 {
-       struct extent_record *rec;
-       struct tree_backref *back;
-       struct cache_extent *cache;
-
-       cache = lookup_cache_extent(extent_cache, bytenr, 1);
-       if (!cache) {
-               add_extent_rec_nolookup(extent_cache, NULL, 0, bytenr,
-                              1, 0, 0, 0, 0, 1, 0, 0);
-               cache = lookup_cache_extent(extent_cache, bytenr, 1);
-               if (!cache)
-                       abort();
-       }
-
-       rec = container_of(cache, struct extent_record, cache);
-       if (rec->start != bytenr) {
-               abort();
-       }
-
-       back = find_tree_backref(rec, parent, root);
-       if (!back) {
-               back = alloc_tree_backref(rec, parent, root);
-               BUG_ON(!back);
-       }
-
-       if (found_ref) {
-               if (back->node.found_ref) {
-                       fprintf(stderr, "Extent back ref already exists "
-                               "for %llu parent %llu root %llu \n",
-                               (unsigned long long)bytenr,
-                               (unsigned long long)parent,
-                               (unsigned long long)root);
-               }
-               back->node.found_ref = 1;
-       } else {
-               if (back->node.found_extent_tree) {
-                       fprintf(stderr, "Extent back ref already exists "
-                               "for %llu parent %llu root %llu \n",
-                               (unsigned long long)bytenr,
-                               (unsigned long long)parent,
-                               (unsigned long long)root);
-               }
-               back->node.found_extent_tree = 1;
+       struct extent_backref *back;
+       struct list_head *cur;
+       while (!list_empty(&rec->backrefs)) {
+               cur = rec->backrefs.next;
+               back = to_extent_backref(cur);
+               list_del(cur);
+               free(back);
        }
-       check_extent_type(rec);
-       maybe_free_extent_rec(extent_cache, rec);
        return 0;
 }
 
-static int add_data_backref(struct cache_tree *extent_cache, u64 bytenr,
-                           u64 parent, u64 root, u64 owner, u64 offset,
-                           u32 num_refs, int found_ref, u64 max_size)
+static void free_extent_record_cache(struct btrfs_fs_info *fs_info,
+                                    struct cache_tree *extent_cache)
 {
-       struct extent_record *rec;
-       struct data_backref *back;
        struct cache_extent *cache;
+       struct extent_record *rec;
 
-       cache = lookup_cache_extent(extent_cache, bytenr, 1);
-       if (!cache) {
-               add_extent_rec_nolookup(extent_cache, NULL, 0, bytenr, 1, 0, 0,
-                               0, 0, 0, 0, max_size);
-               cache = lookup_cache_extent(extent_cache, bytenr, 1);
+       while (1) {
+               cache = first_cache_extent(extent_cache);
                if (!cache)
-                       abort();
-       }
-
-       rec = container_of(cache, struct extent_record, cache);
-       if (rec->max_size < max_size)
-               rec->max_size = max_size;
-
-       /*
-        * If found_ref is set then max_size is the real size and must match the
-        * existing refs.  So if we have already found a ref then we need to
-        * make sure that this ref matches the existing one, otherwise we need
-        * to add a new backref so we can notice that the backrefs don't match
-        * and we need to figure out who is telling the truth.  This is to
-        * account for that awful fsync bug I introduced where we'd end up with
-        * a btrfs_file_extent_item that would have its length include multiple
-        * prealloc extents or point inside of a prealloc extent.
-        */
-       back = find_data_backref(rec, parent, root, owner, offset, found_ref,
-                                bytenr, max_size);
-       if (!back) {
-               back = alloc_data_backref(rec, parent, root, owner, offset,
-                                         max_size);
-               BUG_ON(!back);
-       }
-
-       if (found_ref) {
-               BUG_ON(num_refs != 1);
-               if (back->node.found_ref)
-                       BUG_ON(back->bytes != max_size);
-               back->node.found_ref = 1;
-               back->found_ref += 1;
-               back->bytes = max_size;
-               back->disk_bytenr = bytenr;
-               rec->refs += 1;
-               rec->content_checked = 1;
-               rec->owner_ref_checked = 1;
-       } else {
-               if (back->node.found_extent_tree) {
-                       fprintf(stderr, "Extent back ref already exists "
-                               "for %llu parent %llu root %llu "
-                               "owner %llu offset %llu num_refs %lu\n",
-                               (unsigned long long)bytenr,
-                               (unsigned long long)parent,
-                               (unsigned long long)root,
-                               (unsigned long long)owner,
-                               (unsigned long long)offset,
-                               (unsigned long)num_refs);
-               }
-               back->num_refs = num_refs;
-               back->node.found_extent_tree = 1;
+                       break;
+               rec = container_of(cache, struct extent_record, cache);
+               remove_cache_extent(extent_cache, cache);
+               free_all_extent_backrefs(rec);
+               free(rec);
        }
-       maybe_free_extent_rec(extent_cache, rec);
-       return 0;
 }
 
-static int add_pending(struct cache_tree *pending,
-                      struct cache_tree *seen, u64 bytenr, u32 size)
+static int maybe_free_extent_rec(struct cache_tree *extent_cache,
+                                struct extent_record *rec)
 {
-       int ret;
-       ret = add_cache_extent(seen, bytenr, size);
-       if (ret)
-               return ret;
-       add_cache_extent(pending, bytenr, size);
+       if (rec->content_checked && rec->owner_ref_checked &&
+           rec->extent_item_refs == rec->refs && rec->refs > 0 &&
+           rec->num_duplicates == 0 && !all_backpointers_checked(rec, 0) &&
+           !rec->bad_full_backref && !rec->crossing_stripes &&
+           !rec->wrong_chunk_type) {
+               remove_cache_extent(extent_cache, &rec->cache);
+               free_all_extent_backrefs(rec);
+               list_del_init(&rec->list);
+               free(rec);
+       }
        return 0;
 }
 
-static int pick_next_pending(struct cache_tree *pending,
-                       struct cache_tree *reada,
-                       struct cache_tree *nodes,
-                       u64 last, struct block_info *bits, int bits_nr,
-                       int *reada_bits)
+static int check_owner_ref(struct btrfs_root *root,
+                           struct extent_record *rec,
+                           struct extent_buffer *buf)
 {
-       unsigned long node_start = last;
-       struct cache_extent *cache;
+       struct extent_backref *node;
+       struct tree_backref *back;
+       struct btrfs_root *ref_root;
+       struct btrfs_key key;
+       struct btrfs_path path;
+       struct extent_buffer *parent;
+       int level;
+       int found = 0;
        int ret;
 
-       cache = search_cache_extent(reada, 0);
-       if (cache) {
-               bits[0].start = cache->start;
-               bits[0].size = cache->size;
-               *reada_bits = 1;
-               return 1;
+       list_for_each_entry(node, &rec->backrefs, list) {
+               if (node->is_data)
+                       continue;
+               if (!node->found_ref)
+                       continue;
+               if (node->full_backref)
+                       continue;
+               back = to_tree_backref(node);
+               if (btrfs_header_owner(buf) == back->root)
+                       return 0;
        }
-       *reada_bits = 0;
-       if (node_start > 32768)
-               node_start -= 32768;
+       BUG_ON(rec->is_root);
 
-       cache = search_cache_extent(nodes, node_start);
-       if (!cache)
-               cache = search_cache_extent(nodes, 0);
+       /* try to find the block by search corresponding fs tree */
+       key.objectid = btrfs_header_owner(buf);
+       key.type = BTRFS_ROOT_ITEM_KEY;
+       key.offset = (u64)-1;
 
-       if (!cache) {
-                cache = search_cache_extent(pending, 0);
-                if (!cache)
-                        return 0;
-                ret = 0;
-                do {
-                        bits[ret].start = cache->start;
-                        bits[ret].size = cache->size;
-                        cache = next_cache_extent(cache);
-                        ret++;
-                } while (cache && ret < bits_nr);
-                return ret;
-       }
+       ref_root = btrfs_read_fs_root(root->fs_info, &key);
+       if (IS_ERR(ref_root))
+               return 1;
 
-       ret = 0;
-       do {
-               bits[ret].start = cache->start;
-               bits[ret].size = cache->size;
-               cache = next_cache_extent(cache);
-               ret++;
-       } while (cache && ret < bits_nr);
+       level = btrfs_header_level(buf);
+       if (level == 0)
+               btrfs_item_key_to_cpu(buf, &key, 0);
+       else
+               btrfs_node_key_to_cpu(buf, &key, 0);
 
-       if (bits_nr - ret > 8) {
-               u64 lookup = bits[0].start + bits[0].size;
-               struct cache_extent *next;
-               next = search_cache_extent(pending, lookup);
-               while(next) {
-                       if (next->start - lookup > 32768)
-                               break;
-                       bits[ret].start = next->start;
-                       bits[ret].size = next->size;
-                       lookup = next->start + next->size;
-                       ret++;
-                       if (ret == bits_nr)
-                               break;
-                       next = next_cache_extent(next);
-                       if (!next)
-                               break;
-               }
-       }
-       return ret;
-}
+       btrfs_init_path(&path);
+       path.lowest_level = level + 1;
+       ret = btrfs_search_slot(NULL, ref_root, &key, &path, 0, 0);
+       if (ret < 0)
+               return 0;
 
-static void free_chunk_record(struct cache_extent *cache)
-{
-       struct chunk_record *rec;
+       parent = path.nodes[level + 1];
+       if (parent && buf->start == btrfs_node_blockptr(parent,
+                                                       path.slots[level + 1]))
+               found = 1;
 
-       rec = container_of(cache, struct chunk_record, cache);
-       list_del_init(&rec->list);
-       list_del_init(&rec->dextents);
-       free(rec);
+       btrfs_release_path(&path);
+       return found ? 0 : 1;
 }
 
-void free_chunk_cache_tree(struct cache_tree *chunk_cache)
+static int is_extent_tree_record(struct extent_record *rec)
 {
-       cache_tree_free_extents(chunk_cache, free_chunk_record);
-}
-
-static void free_device_record(struct rb_node *node)
-{
-       struct device_record *rec;
+       struct list_head *cur = rec->backrefs.next;
+       struct extent_backref *node;
+       struct tree_backref *back;
+       int is_extent = 0;
 
-       rec = container_of(node, struct device_record, node);
-       free(rec);
+       while(cur != &rec->backrefs) {
+               node = to_extent_backref(cur);
+               cur = cur->next;
+               if (node->is_data)
+                       return 0;
+               back = to_tree_backref(node);
+               if (node->full_backref)
+                       return 0;
+               if (back->root == BTRFS_EXTENT_TREE_OBJECTID)
+                       is_extent = 1;
+       }
+       return is_extent;
 }
 
-FREE_RB_BASED_TREE(device_cache, free_device_record);
 
-int insert_block_group_record(struct block_group_tree *tree,
-                             struct block_group_record *bg_rec)
+static int record_bad_block_io(struct btrfs_fs_info *info,
+                              struct cache_tree *extent_cache,
+                              u64 start, u64 len)
 {
-       int ret;
-
-       ret = insert_cache_extent(&tree->tree, &bg_rec->cache);
-       if (ret)
-               return ret;
-
-       list_add_tail(&bg_rec->list, &tree->block_groups);
-       return 0;
-}
+       struct extent_record *rec;
+       struct cache_extent *cache;
+       struct btrfs_key key;
 
-static void free_block_group_record(struct cache_extent *cache)
-{
-       struct block_group_record *rec;
+       cache = lookup_cache_extent(extent_cache, start, len);
+       if (!cache)
+               return 0;
 
-       rec = container_of(cache, struct block_group_record, cache);
-       list_del_init(&rec->list);
-       free(rec);
-}
+       rec = container_of(cache, struct extent_record, cache);
+       if (!is_extent_tree_record(rec))
+               return 0;
 
-void free_block_group_tree(struct block_group_tree *tree)
-{
-       cache_tree_free_extents(&tree->tree, free_block_group_record);
+       btrfs_disk_key_to_cpu(&key, &rec->parent_key);
+       return btrfs_add_corrupt_extent_record(info, &key, start, len, 0);
 }
 
-int insert_device_extent_record(struct device_extent_tree *tree,
-                               struct device_extent_record *de_rec)
+static int swap_values(struct btrfs_root *root, struct btrfs_path *path,
+                      struct extent_buffer *buf, int slot)
 {
-       int ret;
+       if (btrfs_header_level(buf)) {
+               struct btrfs_key_ptr ptr1, ptr2;
 
-       /*
-        * Device extent is a bit different from the other extents, because
-        * the extents which belong to the different devices may have the
-        * same start and size, so we need use the special extent cache
-        * search/insert functions.
-        */
-       ret = insert_cache_extent2(&tree->tree, &de_rec->cache);
-       if (ret)
-               return ret;
+               read_extent_buffer(buf, &ptr1, btrfs_node_key_ptr_offset(slot),
+                                  sizeof(struct btrfs_key_ptr));
+               read_extent_buffer(buf, &ptr2,
+                                  btrfs_node_key_ptr_offset(slot + 1),
+                                  sizeof(struct btrfs_key_ptr));
+               write_extent_buffer(buf, &ptr1,
+                                   btrfs_node_key_ptr_offset(slot + 1),
+                                   sizeof(struct btrfs_key_ptr));
+               write_extent_buffer(buf, &ptr2,
+                                   btrfs_node_key_ptr_offset(slot),
+                                   sizeof(struct btrfs_key_ptr));
+               if (slot == 0) {
+                       struct btrfs_disk_key key;
+                       btrfs_node_key(buf, &key, 0);
+                       btrfs_fixup_low_keys(root, path, &key,
+                                            btrfs_header_level(buf) + 1);
+               }
+       } else {
+               struct btrfs_item *item1, *item2;
+               struct btrfs_key k1, k2;
+               char *item1_data, *item2_data;
+               u32 item1_offset, item2_offset, item1_size, item2_size;
 
-       list_add_tail(&de_rec->chunk_list, &tree->no_chunk_orphans);
-       list_add_tail(&de_rec->device_list, &tree->no_device_orphans);
-       return 0;
-}
+               item1 = btrfs_item_nr(slot);
+               item2 = btrfs_item_nr(slot + 1);
+               btrfs_item_key_to_cpu(buf, &k1, slot);
+               btrfs_item_key_to_cpu(buf, &k2, slot + 1);
+               item1_offset = btrfs_item_offset(buf, item1);
+               item2_offset = btrfs_item_offset(buf, item2);
+               item1_size = btrfs_item_size(buf, item1);
+               item2_size = btrfs_item_size(buf, item2);
 
-static void free_device_extent_record(struct cache_extent *cache)
-{
-       struct device_extent_record *rec;
+               item1_data = malloc(item1_size);
+               if (!item1_data)
+                       return -ENOMEM;
+               item2_data = malloc(item2_size);
+               if (!item2_data) {
+                       free(item1_data);
+                       return -ENOMEM;
+               }
 
-       rec = container_of(cache, struct device_extent_record, cache);
-       if (!list_empty(&rec->chunk_list))
-               list_del_init(&rec->chunk_list);
-       if (!list_empty(&rec->device_list))
-               list_del_init(&rec->device_list);
-       free(rec);
-}
+               read_extent_buffer(buf, item1_data, item1_offset, item1_size);
+               read_extent_buffer(buf, item2_data, item2_offset, item2_size);
 
-void free_device_extent_tree(struct device_extent_tree *tree)
-{
-       cache_tree_free_extents(&tree->tree, free_device_extent_record);
-}
+               write_extent_buffer(buf, item1_data, item2_offset, item2_size);
+               write_extent_buffer(buf, item2_data, item1_offset, item1_size);
+               free(item1_data);
+               free(item2_data);
 
-#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
-static int process_extent_ref_v0(struct cache_tree *extent_cache,
-                                struct extent_buffer *leaf, int slot)
-{
-       struct btrfs_extent_ref_v0 *ref0;
-       struct btrfs_key key;
+               btrfs_set_item_offset(buf, item1, item2_offset);
+               btrfs_set_item_offset(buf, item2, item1_offset);
+               btrfs_set_item_size(buf, item1, item2_size);
+               btrfs_set_item_size(buf, item2, item1_size);
 
-       btrfs_item_key_to_cpu(leaf, &key, slot);
-       ref0 = btrfs_item_ptr(leaf, slot, struct btrfs_extent_ref_v0);
-       if (btrfs_ref_objectid_v0(leaf, ref0) < BTRFS_FIRST_FREE_OBJECTID) {
-               add_tree_backref(extent_cache, key.objectid, key.offset, 0, 0);
-       } else {
-               add_data_backref(extent_cache, key.objectid, key.offset, 0,
-                                0, 0, btrfs_ref_count_v0(leaf, ref0), 0, 0);
+               path->slots[0] = slot;
+               btrfs_set_item_key_unsafe(root, path, &k2);
+               path->slots[0] = slot + 1;
+               btrfs_set_item_key_unsafe(root, path, &k1);
        }
        return 0;
 }
-#endif
 
-struct chunk_record *btrfs_new_chunk_record(struct extent_buffer *leaf,
-                                           struct btrfs_key *key,
-                                           int slot)
+static int fix_key_order(struct btrfs_trans_handle *trans,
+                        struct btrfs_root *root,
+                        struct btrfs_path *path)
 {
-       struct btrfs_chunk *ptr;
-       struct chunk_record *rec;
-       int num_stripes, i;
-
-       ptr = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
-       num_stripes = btrfs_chunk_num_stripes(leaf, ptr);
+       struct extent_buffer *buf;
+       struct btrfs_key k1, k2;
+       int i;
+       int level = path->lowest_level;
+       int ret = -EIO;
 
-       rec = calloc(1, btrfs_chunk_record_size(num_stripes));
-       if (!rec) {
-               fprintf(stderr, "memory allocation failed\n");
-               exit(-1);
+       buf = path->nodes[level];
+       for (i = 0; i < btrfs_header_nritems(buf) - 1; i++) {
+               if (level) {
+                       btrfs_node_key_to_cpu(buf, &k1, i);
+                       btrfs_node_key_to_cpu(buf, &k2, i + 1);
+               } else {
+                       btrfs_item_key_to_cpu(buf, &k1, i);
+                       btrfs_item_key_to_cpu(buf, &k2, i + 1);
+               }
+               if (btrfs_comp_cpu_keys(&k1, &k2) < 0)
+                       continue;
+               ret = swap_values(root, path, buf, i);
+               if (ret)
+                       break;
+               btrfs_mark_buffer_dirty(buf);
+               i = 0;
        }
+       return ret;
+}
 
-       INIT_LIST_HEAD(&rec->list);
-       INIT_LIST_HEAD(&rec->dextents);
-       rec->bg_rec = NULL;
-
-       rec->cache.start = key->offset;
-       rec->cache.size = btrfs_chunk_length(leaf, ptr);
+static int delete_bogus_item(struct btrfs_trans_handle *trans,
+                            struct btrfs_root *root,
+                            struct btrfs_path *path,
+                            struct extent_buffer *buf, int slot)
+{
+       struct btrfs_key key;
+       int nritems = btrfs_header_nritems(buf);
 
-       rec->generation = btrfs_header_generation(leaf);
+       btrfs_item_key_to_cpu(buf, &key, slot);
 
-       rec->objectid = key->objectid;
-       rec->type = key->type;
-       rec->offset = key->offset;
+       /* These are all the keys we can deal with missing. */
+       if (key.type != BTRFS_DIR_INDEX_KEY &&
+           key.type != BTRFS_EXTENT_ITEM_KEY &&
+           key.type != BTRFS_METADATA_ITEM_KEY &&
+           key.type != BTRFS_TREE_BLOCK_REF_KEY &&
+           key.type != BTRFS_EXTENT_DATA_REF_KEY)
+               return -1;
 
-       rec->length = rec->cache.size;
-       rec->owner = btrfs_chunk_owner(leaf, ptr);
-       rec->stripe_len = btrfs_chunk_stripe_len(leaf, ptr);
-       rec->type_flags = btrfs_chunk_type(leaf, ptr);
-       rec->io_width = btrfs_chunk_io_width(leaf, ptr);
-       rec->io_align = btrfs_chunk_io_align(leaf, ptr);
-       rec->sector_size = btrfs_chunk_sector_size(leaf, ptr);
-       rec->num_stripes = num_stripes;
-       rec->sub_stripes = btrfs_chunk_sub_stripes(leaf, ptr);
+       printf("Deleting bogus item [%llu,%u,%llu] at slot %d on block %llu\n",
+              (unsigned long long)key.objectid, key.type,
+              (unsigned long long)key.offset, slot, buf->start);
+       memmove_extent_buffer(buf, btrfs_item_nr_offset(slot),
+                             btrfs_item_nr_offset(slot + 1),
+                             sizeof(struct btrfs_item) *
+                             (nritems - slot - 1));
+       btrfs_set_header_nritems(buf, nritems - 1);
+       if (slot == 0) {
+               struct btrfs_disk_key disk_key;
 
-       for (i = 0; i < rec->num_stripes; ++i) {
-               rec->stripes[i].devid =
-                       btrfs_stripe_devid_nr(leaf, ptr, i);
-               rec->stripes[i].offset =
-                       btrfs_stripe_offset_nr(leaf, ptr, i);
-               read_extent_buffer(leaf, rec->stripes[i].dev_uuid,
-                               (unsigned long)btrfs_stripe_dev_uuid_nr(ptr, i),
-                               BTRFS_UUID_SIZE);
+               btrfs_item_key(buf, &disk_key, 0);
+               btrfs_fixup_low_keys(root, path, &disk_key, 1);
        }
-
-       return rec;
+       btrfs_mark_buffer_dirty(buf);
+       return 0;
 }
 
-static int process_chunk_item(struct cache_tree *chunk_cache,
-                             struct btrfs_key *key, struct extent_buffer *eb,
-                             int slot)
-{
-       struct chunk_record *rec;
+static int fix_item_offset(struct btrfs_trans_handle *trans,
+                          struct btrfs_root *root,
+                          struct btrfs_path *path)
+{
+       struct extent_buffer *buf;
+       int i;
        int ret = 0;
 
-       rec = btrfs_new_chunk_record(eb, key, slot);
-       ret = insert_cache_extent(chunk_cache, &rec->cache);
-       if (ret) {
-               fprintf(stderr, "Chunk[%llu, %llu] existed.\n",
-                       rec->offset, rec->length);
-               free(rec);
+       /* We should only get this for leaves */
+       BUG_ON(path->lowest_level);
+       buf = path->nodes[0];
+again:
+       for (i = 0; i < btrfs_header_nritems(buf); i++) {
+               unsigned int shift = 0, offset;
+
+               if (i == 0 && btrfs_item_end_nr(buf, i) !=
+                   BTRFS_LEAF_DATA_SIZE(root)) {
+                       if (btrfs_item_end_nr(buf, i) >
+                           BTRFS_LEAF_DATA_SIZE(root)) {
+                               ret = delete_bogus_item(trans, root, path,
+                                                       buf, i);
+                               if (!ret)
+                                       goto again;
+                               fprintf(stderr, "item is off the end of the "
+                                       "leaf, can't fix\n");
+                               ret = -EIO;
+                               break;
+                       }
+                       shift = BTRFS_LEAF_DATA_SIZE(root) -
+                               btrfs_item_end_nr(buf, i);
+               } else if (i > 0 && btrfs_item_end_nr(buf, i) !=
+                          btrfs_item_offset_nr(buf, i - 1)) {
+                       if (btrfs_item_end_nr(buf, i) >
+                           btrfs_item_offset_nr(buf, i - 1)) {
+                               ret = delete_bogus_item(trans, root, path,
+                                                       buf, i);
+                               if (!ret)
+                                       goto again;
+                               fprintf(stderr, "items overlap, can't fix\n");
+                               ret = -EIO;
+                               break;
+                       }
+                       shift = btrfs_item_offset_nr(buf, i - 1) -
+                               btrfs_item_end_nr(buf, i);
+               }
+               if (!shift)
+                       continue;
+
+               printf("Shifting item nr %d by %u bytes in block %llu\n",
+                      i, shift, (unsigned long long)buf->start);
+               offset = btrfs_item_offset_nr(buf, i);
+               memmove_extent_buffer(buf,
+                                     btrfs_leaf_data(buf) + offset + shift,
+                                     btrfs_leaf_data(buf) + offset,
+                                     btrfs_item_size_nr(buf, i));
+               btrfs_set_item_offset(buf, btrfs_item_nr(i),
+                                     offset + shift);
+               btrfs_mark_buffer_dirty(buf);
        }
 
+       /*
+        * We may have moved things, in which case we want to exit so we don't
+        * write those changes out.  Once we have proper abort functionality in
+        * progs this can be changed to something nicer.
+        */
+       BUG_ON(ret);
        return ret;
 }
 
-static int process_device_item(struct rb_root *dev_cache,
-               struct btrfs_key *key, struct extent_buffer *eb, int slot)
+/*
+ * Attempt to fix basic block failures.  If we can't fix it for whatever reason
+ * then just return -EIO.
+ */
+static int try_to_fix_bad_block(struct btrfs_root *root,
+                               struct extent_buffer *buf,
+                               enum btrfs_tree_block_status status)
 {
-       struct btrfs_dev_item *ptr;
-       struct device_record *rec;
-       int ret = 0;
+       struct btrfs_trans_handle *trans;
+       struct ulist *roots;
+       struct ulist_node *node;
+       struct btrfs_root *search_root;
+       struct btrfs_path path;
+       struct ulist_iterator iter;
+       struct btrfs_key root_key, key;
+       int ret;
 
-       ptr = btrfs_item_ptr(eb,
-               slot, struct btrfs_dev_item);
+       if (status != BTRFS_TREE_BLOCK_BAD_KEY_ORDER &&
+           status != BTRFS_TREE_BLOCK_INVALID_OFFSETS)
+               return -EIO;
 
-       rec = malloc(sizeof(*rec));
-       if (!rec) {
-               fprintf(stderr, "memory allocation failed\n");
-               return -ENOMEM;
-       }
+       ret = btrfs_find_all_roots(NULL, root->fs_info, buf->start, 0, &roots);
+       if (ret)
+               return -EIO;
 
-       rec->devid = key->offset;
-       rec->generation = btrfs_header_generation(eb);
+       btrfs_init_path(&path);
+       ULIST_ITER_INIT(&iter);
+       while ((node = ulist_next(roots, &iter))) {
+               root_key.objectid = node->val;
+               root_key.type = BTRFS_ROOT_ITEM_KEY;
+               root_key.offset = (u64)-1;
 
-       rec->objectid = key->objectid;
-       rec->type = key->type;
-       rec->offset = key->offset;
+               search_root = btrfs_read_fs_root(root->fs_info, &root_key);
+               if (IS_ERR(root)) {
+                       ret = -EIO;
+                       break;
+               }
 
-       rec->devid = btrfs_device_id(eb, ptr);
-       rec->total_byte = btrfs_device_total_bytes(eb, ptr);
-       rec->byte_used = btrfs_device_bytes_used(eb, ptr);
 
-       ret = rb_insert(dev_cache, &rec->node, device_record_compare);
-       if (ret) {
-               fprintf(stderr, "Device[%llu] existed.\n", rec->devid);
-               free(rec);
-       }
+               trans = btrfs_start_transaction(search_root, 0);
+               if (IS_ERR(trans)) {
+                       ret = PTR_ERR(trans);
+                       break;
+               }
 
+               path.lowest_level = btrfs_header_level(buf);
+               path.skip_check_block = 1;
+               if (path.lowest_level)
+                       btrfs_node_key_to_cpu(buf, &key, 0);
+               else
+                       btrfs_item_key_to_cpu(buf, &key, 0);
+               ret = btrfs_search_slot(trans, search_root, &key, &path, 0, 1);
+               if (ret) {
+                       ret = -EIO;
+                       btrfs_commit_transaction(trans, search_root);
+                       break;
+               }
+               if (status == BTRFS_TREE_BLOCK_BAD_KEY_ORDER)
+                       ret = fix_key_order(trans, search_root, &path);
+               else if (status == BTRFS_TREE_BLOCK_INVALID_OFFSETS)
+                       ret = fix_item_offset(trans, search_root, &path);
+               if (ret) {
+                       btrfs_commit_transaction(trans, search_root);
+                       break;
+               }
+               btrfs_release_path(&path);
+               btrfs_commit_transaction(trans, search_root);
+       }
+       ulist_free(roots);
+       btrfs_release_path(&path);
        return ret;
 }
 
-struct block_group_record *
-btrfs_new_block_group_record(struct extent_buffer *leaf, struct btrfs_key *key,
-                            int slot)
+static int check_block(struct btrfs_root *root,
+                      struct cache_tree *extent_cache,
+                      struct extent_buffer *buf, u64 flags)
 {
-       struct btrfs_block_group_item *ptr;
-       struct block_group_record *rec;
-
-       rec = calloc(1, sizeof(*rec));
-       if (!rec) {
-               fprintf(stderr, "memory allocation failed\n");
-               exit(-1);
-       }
+       struct extent_record *rec;
+       struct cache_extent *cache;
+       struct btrfs_key key;
+       enum btrfs_tree_block_status status;
+       int ret = 0;
+       int level;
 
-       rec->cache.start = key->objectid;
-       rec->cache.size = key->offset;
+       cache = lookup_cache_extent(extent_cache, buf->start, buf->len);
+       if (!cache)
+               return 1;
+       rec = container_of(cache, struct extent_record, cache);
+       rec->generation = btrfs_header_generation(buf);
 
-       rec->generation = btrfs_header_generation(leaf);
+       level = btrfs_header_level(buf);
+       if (btrfs_header_nritems(buf) > 0) {
 
-       rec->objectid = key->objectid;
-       rec->type = key->type;
-       rec->offset = key->offset;
+               if (level == 0)
+                       btrfs_item_key_to_cpu(buf, &key, 0);
+               else
+                       btrfs_node_key_to_cpu(buf, &key, 0);
 
-       ptr = btrfs_item_ptr(leaf, slot, struct btrfs_block_group_item);
-       rec->flags = btrfs_disk_block_group_flags(leaf, ptr);
+               rec->info_objectid = key.objectid;
+       }
+       rec->info_level = level;
 
-       INIT_LIST_HEAD(&rec->list);
+       if (btrfs_is_leaf(buf))
+               status = btrfs_check_leaf(root, &rec->parent_key, buf);
+       else
+               status = btrfs_check_node(root, &rec->parent_key, buf);
 
-       return rec;
+       if (status != BTRFS_TREE_BLOCK_CLEAN) {
+               if (repair)
+                       status = try_to_fix_bad_block(root, buf, status);
+               if (status != BTRFS_TREE_BLOCK_CLEAN) {
+                       ret = -EIO;
+                       fprintf(stderr, "bad block %llu\n",
+                               (unsigned long long)buf->start);
+               } else {
+                       /*
+                        * Signal to callers we need to start the scan over
+                        * again since we'll have cowed blocks.
+                        */
+                       ret = -EAGAIN;
+               }
+       } else {
+               rec->content_checked = 1;
+               if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
+                       rec->owner_ref_checked = 1;
+               else {
+                       ret = check_owner_ref(root, rec, buf);
+                       if (!ret)
+                               rec->owner_ref_checked = 1;
+               }
+       }
+       if (!ret)
+               maybe_free_extent_rec(extent_cache, rec);
+       return ret;
 }
 
-static int process_block_group_item(struct block_group_tree *block_group_cache,
-                                   struct btrfs_key *key,
-                                   struct extent_buffer *eb, int slot)
+static struct tree_backref *find_tree_backref(struct extent_record *rec,
+                                               u64 parent, u64 root)
 {
-       struct block_group_record *rec;
-       int ret = 0;
+       struct list_head *cur = rec->backrefs.next;
+       struct extent_backref *node;
+       struct tree_backref *back;
 
-       rec = btrfs_new_block_group_record(eb, key, slot);
-       ret = insert_block_group_record(block_group_cache, rec);
-       if (ret) {
-               fprintf(stderr, "Block Group[%llu, %llu] existed.\n",
-                       rec->objectid, rec->offset);
-               free(rec);
+       while(cur != &rec->backrefs) {
+               node = to_extent_backref(cur);
+               cur = cur->next;
+               if (node->is_data)
+                       continue;
+               back = to_tree_backref(node);
+               if (parent > 0) {
+                       if (!node->full_backref)
+                               continue;
+                       if (parent == back->parent)
+                               return back;
+               } else {
+                       if (node->full_backref)
+                               continue;
+                       if (back->root == root)
+                               return back;
+               }
        }
-
-       return ret;
+       return NULL;
 }
 
-struct device_extent_record *
-btrfs_new_device_extent_record(struct extent_buffer *leaf,
-                              struct btrfs_key *key, int slot)
+static struct tree_backref *alloc_tree_backref(struct extent_record *rec,
+                                               u64 parent, u64 root)
 {
-       struct device_extent_record *rec;
-       struct btrfs_dev_extent *ptr;
+       struct tree_backref *ref = malloc(sizeof(*ref));
 
-       rec = calloc(1, sizeof(*rec));
-       if (!rec) {
-               fprintf(stderr, "memory allocation failed\n");
-               exit(-1);
+       if (!ref)
+               return NULL;
+       memset(&ref->node, 0, sizeof(ref->node));
+       if (parent > 0) {
+               ref->parent = parent;
+               ref->node.full_backref = 1;
+       } else {
+               ref->root = root;
+               ref->node.full_backref = 0;
        }
+       list_add_tail(&ref->node.list, &rec->backrefs);
 
-       rec->cache.objectid = key->objectid;
-       rec->cache.start = key->offset;
-
-       rec->generation = btrfs_header_generation(leaf);
-
-       rec->objectid = key->objectid;
-       rec->type = key->type;
-       rec->offset = key->offset;
-
-       ptr = btrfs_item_ptr(leaf, slot, struct btrfs_dev_extent);
-       rec->chunk_objecteid =
-               btrfs_dev_extent_chunk_objectid(leaf, ptr);
-       rec->chunk_offset =
-               btrfs_dev_extent_chunk_offset(leaf, ptr);
-       rec->length = btrfs_dev_extent_length(leaf, ptr);
-       rec->cache.size = rec->length;
-
-       INIT_LIST_HEAD(&rec->chunk_list);
-       INIT_LIST_HEAD(&rec->device_list);
-
-       return rec;
+       return ref;
 }
 
-static int
-process_device_extent_item(struct device_extent_tree *dev_extent_cache,
-                          struct btrfs_key *key, struct extent_buffer *eb,
-                          int slot)
+static struct data_backref *find_data_backref(struct extent_record *rec,
+                                               u64 parent, u64 root,
+                                               u64 owner, u64 offset,
+                                               int found_ref,
+                                               u64 disk_bytenr, u64 bytes)
 {
-       struct device_extent_record *rec;
-       int ret;
+       struct list_head *cur = rec->backrefs.next;
+       struct extent_backref *node;
+       struct data_backref *back;
 
-       rec = btrfs_new_device_extent_record(eb, key, slot);
-       ret = insert_device_extent_record(dev_extent_cache, rec);
-       if (ret) {
-               fprintf(stderr,
-                       "Device extent[%llu, %llu, %llu] existed.\n",
-                       rec->objectid, rec->offset, rec->length);
-               free(rec);
+       while(cur != &rec->backrefs) {
+               node = to_extent_backref(cur);
+               cur = cur->next;
+               if (!node->is_data)
+                       continue;
+               back = to_data_backref(node);
+               if (parent > 0) {
+                       if (!node->full_backref)
+                               continue;
+                       if (parent == back->parent)
+                               return back;
+               } else {
+                       if (node->full_backref)
+                               continue;
+                       if (back->root == root && back->owner == owner &&
+                           back->offset == offset) {
+                               if (found_ref && node->found_ref &&
+                                   (back->bytes != bytes ||
+                                   back->disk_bytenr != disk_bytenr))
+                                       continue;
+                               return back;
+                       }
+               }
        }
-
-       return ret;
+       return NULL;
 }
 
-static int process_extent_item(struct btrfs_root *root,
-                              struct cache_tree *extent_cache,
-                              struct extent_buffer *eb, int slot)
+static struct data_backref *alloc_data_backref(struct extent_record *rec,
+                                               u64 parent, u64 root,
+                                               u64 owner, u64 offset,
+                                               u64 max_size)
 {
-       struct btrfs_extent_item *ei;
-       struct btrfs_extent_inline_ref *iref;
-       struct btrfs_extent_data_ref *dref;
-       struct btrfs_shared_data_ref *sref;
-       struct btrfs_key key;
-       unsigned long end;
-       unsigned long ptr;
-       int type;
-       u32 item_size = btrfs_item_size_nr(eb, slot);
-       u64 refs = 0;
-       u64 offset;
-       u64 num_bytes;
-       int metadata = 0;
+       struct data_backref *ref = malloc(sizeof(*ref));
 
-       btrfs_item_key_to_cpu(eb, &key, slot);
+       if (!ref)
+               return NULL;
+       memset(&ref->node, 0, sizeof(ref->node));
+       ref->node.is_data = 1;
 
-       if (key.type == BTRFS_METADATA_ITEM_KEY) {
-               metadata = 1;
-               num_bytes = root->nodesize;
+       if (parent > 0) {
+               ref->parent = parent;
+               ref->owner = 0;
+               ref->offset = 0;
+               ref->node.full_backref = 1;
        } else {
-               num_bytes = key.offset;
+               ref->root = root;
+               ref->owner = owner;
+               ref->offset = offset;
+               ref->node.full_backref = 0;
        }
+       ref->bytes = max_size;
+       ref->found_ref = 0;
+       ref->num_refs = 0;
+       list_add_tail(&ref->node.list, &rec->backrefs);
+       if (max_size > rec->max_size)
+               rec->max_size = max_size;
+       return ref;
+}
 
-       if (item_size < sizeof(*ei)) {
-#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
-               struct btrfs_extent_item_v0 *ei0;
-               BUG_ON(item_size != sizeof(*ei0));
-               ei0 = btrfs_item_ptr(eb, slot, struct btrfs_extent_item_v0);
-               refs = btrfs_extent_refs_v0(eb, ei0);
-#else
-               BUG();
-#endif
-               return add_extent_rec(extent_cache, NULL, 0, key.objectid,
-                                     num_bytes, refs, 0, 0, 0, metadata, 1,
-                                     num_bytes);
-       }
+/* Check if the type of extent matches with its chunk */
+static void check_extent_type(struct extent_record *rec)
+{
+       struct btrfs_block_group_cache *bg_cache;
 
-       ei = btrfs_item_ptr(eb, slot, struct btrfs_extent_item);
-       refs = btrfs_extent_refs(eb, ei);
-       if (btrfs_extent_flags(eb, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK)
-               metadata = 1;
-       else
-               metadata = 0;
+       bg_cache = btrfs_lookup_first_block_group(global_info, rec->start);
+       if (!bg_cache)
+               return;
 
-       add_extent_rec(extent_cache, NULL, 0, key.objectid, num_bytes,
-                      refs, 0, 0, 0, metadata, 1, num_bytes);
+       /* data extent, check chunk directly*/
+       if (!rec->metadata) {
+               if (!(bg_cache->flags & BTRFS_BLOCK_GROUP_DATA))
+                       rec->wrong_chunk_type = 1;
+               return;
+       }
 
-       ptr = (unsigned long)(ei + 1);
-       if (btrfs_extent_flags(eb, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK &&
-           key.type == BTRFS_EXTENT_ITEM_KEY)
-               ptr += sizeof(struct btrfs_tree_block_info);
+       /* metadata extent, check the obvious case first */
+       if (!(bg_cache->flags & (BTRFS_BLOCK_GROUP_SYSTEM |
+                                BTRFS_BLOCK_GROUP_METADATA))) {
+               rec->wrong_chunk_type = 1;
+               return;
+       }
 
-       end = (unsigned long)ei + item_size;
-       while (ptr < end) {
-               iref = (struct btrfs_extent_inline_ref *)ptr;
-               type = btrfs_extent_inline_ref_type(eb, iref);
-               offset = btrfs_extent_inline_ref_offset(eb, iref);
-               switch (type) {
-               case BTRFS_TREE_BLOCK_REF_KEY:
-                       add_tree_backref(extent_cache, key.objectid,
-                                        0, offset, 0);
-                       break;
-               case BTRFS_SHARED_BLOCK_REF_KEY:
-                       add_tree_backref(extent_cache, key.objectid,
-                                        offset, 0, 0);
-                       break;
-               case BTRFS_EXTENT_DATA_REF_KEY:
-                       dref = (struct btrfs_extent_data_ref *)(&iref->offset);
-                       add_data_backref(extent_cache, key.objectid, 0,
-                                       btrfs_extent_data_ref_root(eb, dref),
-                                       btrfs_extent_data_ref_objectid(eb,
-                                                                      dref),
-                                       btrfs_extent_data_ref_offset(eb, dref),
-                                       btrfs_extent_data_ref_count(eb, dref),
-                                       0, num_bytes);
-                       break;
-               case BTRFS_SHARED_DATA_REF_KEY:
-                       sref = (struct btrfs_shared_data_ref *)(iref + 1);
-                       add_data_backref(extent_cache, key.objectid, offset,
-                                       0, 0, 0,
-                                       btrfs_shared_data_ref_count(eb, sref),
-                                       0, num_bytes);
-                       break;
-               default:
-                       fprintf(stderr, "corrupt extent record: key %Lu %u %Lu\n",
-                               key.objectid, key.type, num_bytes);
-                       goto out;
+       /*
+        * Check SYSTEM extent, as it's also marked as metadata, we can only
+        * make sure it's a SYSTEM extent by its backref
+        */
+       if (!list_empty(&rec->backrefs)) {
+               struct extent_backref *node;
+               struct tree_backref *tback;
+               u64 bg_type;
+
+               node = to_extent_backref(rec->backrefs.next);
+               if (node->is_data) {
+                       /* tree block shouldn't have data backref */
+                       rec->wrong_chunk_type = 1;
+                       return;
                }
-               ptr += btrfs_extent_inline_ref_size(type);
+               tback = container_of(node, struct tree_backref, node);
+
+               if (tback->root == BTRFS_CHUNK_TREE_OBJECTID)
+                       bg_type = BTRFS_BLOCK_GROUP_SYSTEM;
+               else
+                       bg_type = BTRFS_BLOCK_GROUP_METADATA;
+               if (!(bg_cache->flags & bg_type))
+                       rec->wrong_chunk_type = 1;
        }
-       WARN_ON(ptr > end);
-out:
-       return 0;
 }
 
-static int check_cache_range(struct btrfs_root *root,
-                            struct btrfs_block_group_cache *cache,
-                            u64 offset, u64 bytes)
+/*
+ * Allocate a new extent record, fill default values from @tmpl and insert int
+ * @extent_cache. Caller is supposed to make sure the [start,nr) is not in
+ * the cache, otherwise it fails.
+ */
+static int add_extent_rec_nolookup(struct cache_tree *extent_cache,
+               struct extent_record *tmpl)
 {
-       struct btrfs_free_space *entry;
-       u64 *logical;
-       u64 bytenr;
-       int stripe_len;
-       int i, nr, ret;
-
-       for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
-               bytenr = btrfs_sb_offset(i);
-               ret = btrfs_rmap_block(&root->fs_info->mapping_tree,
-                                      cache->key.objectid, bytenr, 0,
-                                      &logical, &nr, &stripe_len);
-               if (ret)
-                       return ret;
+       struct extent_record *rec;
+       int ret = 0;
 
-               while (nr--) {
-                       if (logical[nr] + stripe_len <= offset)
-                               continue;
-                       if (offset + bytes <= logical[nr])
-                               continue;
-                       if (logical[nr] == offset) {
-                               if (stripe_len >= bytes) {
-                                       kfree(logical);
-                                       return 0;
-                               }
-                               bytes -= stripe_len;
-                               offset += stripe_len;
-                       } else if (logical[nr] < offset) {
-                               if (logical[nr] + stripe_len >=
-                                   offset + bytes) {
-                                       kfree(logical);
-                                       return 0;
-                               }
-                               bytes = (offset + bytes) -
-                                       (logical[nr] + stripe_len);
-                               offset = logical[nr] + stripe_len;
-                       } else {
-                               /*
-                                * Could be tricky, the super may land in the
-                                * middle of the area we're checking.  First
-                                * check the easiest case, it's at the end.
-                                */
-                               if (logical[nr] + stripe_len >=
-                                   bytes + offset) {
-                                       bytes = logical[nr] - offset;
-                                       continue;
-                               }
-
-                               /* Check the left side */
-                               ret = check_cache_range(root, cache,
-                                                       offset,
-                                                       logical[nr] - offset);
-                               if (ret) {
-                                       kfree(logical);
-                                       return ret;
-                               }
-
-                               /* Now we continue with the right side */
-                               bytes = (offset + bytes) -
-                                       (logical[nr] + stripe_len);
-                               offset = logical[nr] + stripe_len;
-                       }
-               }
-
-               kfree(logical);
-       }
-
-       entry = btrfs_find_free_space(cache->free_space_ctl, offset, bytes);
-       if (!entry) {
-               fprintf(stderr, "There is no free space entry for %Lu-%Lu\n",
-                       offset, offset+bytes);
-               return -EINVAL;
-       }
-
-       if (entry->offset != offset) {
-               fprintf(stderr, "Wanted offset %Lu, found %Lu\n", offset,
-                       entry->offset);
-               return -EINVAL;
-       }
-
-       if (entry->bytes != bytes) {
-               fprintf(stderr, "Wanted bytes %Lu, found %Lu for off %Lu\n",
-                       bytes, entry->bytes, offset);
-               return -EINVAL;
+       rec = malloc(sizeof(*rec));
+       if (!rec)
+               return -ENOMEM;
+       rec->start = tmpl->start;
+       rec->max_size = tmpl->max_size;
+       rec->nr = max(tmpl->nr, tmpl->max_size);
+       rec->found_rec = tmpl->found_rec;
+       rec->content_checked = tmpl->content_checked;
+       rec->owner_ref_checked = tmpl->owner_ref_checked;
+       rec->num_duplicates = 0;
+       rec->metadata = tmpl->metadata;
+       rec->flag_block_full_backref = FLAG_UNSET;
+       rec->bad_full_backref = 0;
+       rec->crossing_stripes = 0;
+       rec->wrong_chunk_type = 0;
+       rec->is_root = tmpl->is_root;
+       rec->refs = tmpl->refs;
+       rec->extent_item_refs = tmpl->extent_item_refs;
+       rec->parent_generation = tmpl->parent_generation;
+       INIT_LIST_HEAD(&rec->backrefs);
+       INIT_LIST_HEAD(&rec->dups);
+       INIT_LIST_HEAD(&rec->list);
+       memcpy(&rec->parent_key, &tmpl->parent_key, sizeof(tmpl->parent_key));
+       rec->cache.start = tmpl->start;
+       rec->cache.size = tmpl->nr;
+       ret = insert_cache_extent(extent_cache, &rec->cache);
+       if (ret) {
+               free(rec);
+               return ret;
        }
+       bytes_used += rec->nr;
 
-       unlink_free_space(cache->free_space_ctl, entry);
-       free(entry);
-       return 0;
+       if (tmpl->metadata)
+               rec->crossing_stripes = check_crossing_stripes(global_info,
+                               rec->start, global_info->tree_root->nodesize);
+       check_extent_type(rec);
+       return ret;
 }
 
-static int verify_space_cache(struct btrfs_root *root,
-                             struct btrfs_block_group_cache *cache)
+/*
+ * Lookup and modify an extent, some values of @tmpl are interpreted verbatim,
+ * some are hints:
+ * - refs              - if found, increase refs
+ * - is_root           - if found, set
+ * - content_checked   - if found, set
+ * - owner_ref_checked - if found, set
+ *
+ * If not found, create a new one, initialize and insert.
+ */
+static int add_extent_rec(struct cache_tree *extent_cache,
+               struct extent_record *tmpl)
 {
-       struct btrfs_path *path;
-       struct extent_buffer *leaf;
-       struct btrfs_key key;
-       u64 last;
+       struct extent_record *rec;
+       struct cache_extent *cache;
        int ret = 0;
+       int dup = 0;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
-       root = root->fs_info->extent_root;
+       cache = lookup_cache_extent(extent_cache, tmpl->start, tmpl->nr);
+       if (cache) {
+               rec = container_of(cache, struct extent_record, cache);
+               if (tmpl->refs)
+                       rec->refs++;
+               if (rec->nr == 1)
+                       rec->nr = max(tmpl->nr, tmpl->max_size);
 
-       last = max_t(u64, cache->key.objectid, BTRFS_SUPER_INFO_OFFSET);
+               /*
+                * We need to make sure to reset nr to whatever the extent
+                * record says was the real size, this way we can compare it to
+                * the backrefs.
+                */
+               if (tmpl->found_rec) {
+                       if (tmpl->start != rec->start || rec->found_rec) {
+                               struct extent_record *tmp;
 
-       key.objectid = last;
-       key.offset = 0;
-       key.type = BTRFS_EXTENT_ITEM_KEY;
+                               dup = 1;
+                               if (list_empty(&rec->list))
+                                       list_add_tail(&rec->list,
+                                                     &duplicate_extents);
 
-       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-       if (ret < 0)
-               goto out;
-       ret = 0;
-       while (1) {
-               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-                       ret = btrfs_next_leaf(root, path);
-                       if (ret < 0)
-                               goto out;
-                       if (ret > 0) {
-                               ret = 0;
-                               break;
+                               /*
+                                * We have to do this song and dance in case we
+                                * find an extent record that falls inside of
+                                * our current extent record but does not have
+                                * the same objectid.
+                                */
+                               tmp = malloc(sizeof(*tmp));
+                               if (!tmp)
+                                       return -ENOMEM;
+                               tmp->start = tmpl->start;
+                               tmp->max_size = tmpl->max_size;
+                               tmp->nr = tmpl->nr;
+                               tmp->found_rec = 1;
+                               tmp->metadata = tmpl->metadata;
+                               tmp->extent_item_refs = tmpl->extent_item_refs;
+                               INIT_LIST_HEAD(&tmp->list);
+                               list_add_tail(&tmp->list, &rec->dups);
+                               rec->num_duplicates++;
+                       } else {
+                               rec->nr = tmpl->nr;
+                               rec->found_rec = 1;
                        }
                }
-               leaf = path->nodes[0];
-               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
-               if (key.objectid >= cache->key.offset + cache->key.objectid)
-                       break;
-               if (key.type != BTRFS_EXTENT_ITEM_KEY &&
-                   key.type != BTRFS_METADATA_ITEM_KEY) {
-                       path->slots[0]++;
-                       continue;
-               }
 
-               if (last == key.objectid) {
-                       if (key.type == BTRFS_EXTENT_ITEM_KEY)
-                               last = key.objectid + key.offset;
-                       else
-                               last = key.objectid + root->nodesize;
-                       path->slots[0]++;
-                       continue;
+               if (tmpl->extent_item_refs && !dup) {
+                       if (rec->extent_item_refs) {
+                               fprintf(stderr, "block %llu rec "
+                                       "extent_item_refs %llu, passed %llu\n",
+                                       (unsigned long long)tmpl->start,
+                                       (unsigned long long)
+                                                       rec->extent_item_refs,
+                                       (unsigned long long)tmpl->extent_item_refs);
+                       }
+                       rec->extent_item_refs = tmpl->extent_item_refs;
                }
+               if (tmpl->is_root)
+                       rec->is_root = 1;
+               if (tmpl->content_checked)
+                       rec->content_checked = 1;
+               if (tmpl->owner_ref_checked)
+                       rec->owner_ref_checked = 1;
+               memcpy(&rec->parent_key, &tmpl->parent_key,
+                               sizeof(tmpl->parent_key));
+               if (tmpl->parent_generation)
+                       rec->parent_generation = tmpl->parent_generation;
+               if (rec->max_size < tmpl->max_size)
+                       rec->max_size = tmpl->max_size;
 
-               ret = check_cache_range(root, cache, last,
-                                       key.objectid - last);
-               if (ret)
-                       break;
-               if (key.type == BTRFS_EXTENT_ITEM_KEY)
-                       last = key.objectid + key.offset;
-               else
-                       last = key.objectid + root->nodesize;
-               path->slots[0]++;
+               /*
+                * A metadata extent can't cross stripe_len boundary, otherwise
+                * kernel scrub won't be able to handle it.
+                * As now stripe_len is fixed to BTRFS_STRIPE_LEN, just check
+                * it.
+                */
+               if (tmpl->metadata)
+                       rec->crossing_stripes = check_crossing_stripes(
+                                       global_info, rec->start,
+                                       global_info->tree_root->nodesize);
+               check_extent_type(rec);
+               maybe_free_extent_rec(extent_cache, rec);
+               return ret;
        }
 
-       if (last < cache->key.objectid + cache->key.offset)
-               ret = check_cache_range(root, cache, last,
-                                       cache->key.objectid +
-                                       cache->key.offset - last);
-
-out:
-       btrfs_free_path(path);
-
-       if (!ret &&
-           !RB_EMPTY_ROOT(&cache->free_space_ctl->free_space_offset)) {
-               fprintf(stderr, "There are still entries left in the space "
-                       "cache\n");
-               ret = -EINVAL;
-       }
+       ret = add_extent_rec_nolookup(extent_cache, tmpl);
 
        return ret;
 }
 
-static int check_space_cache(struct btrfs_root *root)
+static int add_tree_backref(struct cache_tree *extent_cache, u64 bytenr,
+                           u64 parent, u64 root, int found_ref)
 {
-       struct btrfs_block_group_cache *cache;
-       u64 start = BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE;
+       struct extent_record *rec;
+       struct tree_backref *back;
+       struct cache_extent *cache;
        int ret;
-       int error = 0;
 
-       if (btrfs_super_cache_generation(root->fs_info->super_copy) != -1ULL &&
-           btrfs_super_generation(root->fs_info->super_copy) !=
-           btrfs_super_cache_generation(root->fs_info->super_copy)) {
-               printf("cache and super generation don't match, space cache "
-                      "will be invalidated\n");
-               return 0;
-       }
+       cache = lookup_cache_extent(extent_cache, bytenr, 1);
+       if (!cache) {
+               struct extent_record tmpl;
 
-       if (ctx.progress_enabled) {
-               ctx.tp = TASK_FREE_SPACE;
-               task_start(ctx.info);
-       }
+               memset(&tmpl, 0, sizeof(tmpl));
+               tmpl.start = bytenr;
+               tmpl.nr = 1;
+               tmpl.metadata = 1;
 
-       while (1) {
-               cache = btrfs_lookup_first_block_group(root->fs_info, start);
+               ret = add_extent_rec_nolookup(extent_cache, &tmpl);
+               if (ret)
+                       return ret;
+
+               /* really a bug in cache_extent implement now */
+               cache = lookup_cache_extent(extent_cache, bytenr, 1);
                if (!cache)
-                       break;
+                       return -ENOENT;
+       }
 
-               start = cache->key.objectid + cache->key.offset;
-               if (!cache->free_space_ctl) {
-                       if (btrfs_init_free_space_ctl(cache,
-                                                     root->sectorsize)) {
-                               ret = -ENOMEM;
-                               break;
-                       }
-               } else {
-                       btrfs_remove_free_space_cache(cache);
-               }
+       rec = container_of(cache, struct extent_record, cache);
+       if (rec->start != bytenr) {
+               /*
+                * Several cause, from unaligned bytenr to over lapping extents
+                */
+               return -EEXIST;
+       }
 
-               if (btrfs_fs_compat_ro(root->fs_info,
-                                      BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE)) {
-                       ret = exclude_super_stripes(root, cache);
-                       if (ret) {
-                               fprintf(stderr, "could not exclude super stripes: %s\n",
-                                       strerror(-ret));
-                               error++;
-                               continue;
-                       }
-                       ret = load_free_space_tree(root->fs_info, cache);
-                       free_excluded_extents(root, cache);
-                       if (ret < 0) {
-                               fprintf(stderr, "could not load free space tree: %s\n",
-                                       strerror(-ret));
-                               error++;
-                               continue;
-                       }
-                       error += ret;
-               } else {
-                       ret = load_free_space_cache(root->fs_info, cache);
-                       if (!ret)
-                               continue;
-               }
+       back = find_tree_backref(rec, parent, root);
+       if (!back) {
+               back = alloc_tree_backref(rec, parent, root);
+               if (!back)
+                       return -ENOMEM;
+       }
 
-               ret = verify_space_cache(root, cache);
-               if (ret) {
-                       fprintf(stderr, "cache appears valid but isnt %Lu\n",
-                               cache->key.objectid);
-                       error++;
+       if (found_ref) {
+               if (back->node.found_ref) {
+                       fprintf(stderr, "Extent back ref already exists "
+                               "for %llu parent %llu root %llu \n",
+                               (unsigned long long)bytenr,
+                               (unsigned long long)parent,
+                               (unsigned long long)root);
+               }
+               back->node.found_ref = 1;
+       } else {
+               if (back->node.found_extent_tree) {
+                       fprintf(stderr, "Extent back ref already exists "
+                               "for %llu parent %llu root %llu \n",
+                               (unsigned long long)bytenr,
+                               (unsigned long long)parent,
+                               (unsigned long long)root);
                }
+               back->node.found_extent_tree = 1;
        }
-
-       task_stop(ctx.info);
-
-       return error ? -EINVAL : 0;
+       check_extent_type(rec);
+       maybe_free_extent_rec(extent_cache, rec);
+       return 0;
 }
 
-static int check_extent_csums(struct btrfs_root *root, u64 bytenr,
-                       u64 num_bytes, unsigned long leaf_offset,
-                       struct extent_buffer *eb) {
-
-       u64 offset = 0;
-       u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
-       char *data;
-       unsigned long csum_offset;
-       u32 csum;
-       u32 csum_expected;
-       u64 read_len;
-       u64 data_checked = 0;
-       u64 tmp;
-       int ret = 0;
-       int mirror;
-       int num_copies;
+static int add_data_backref(struct cache_tree *extent_cache, u64 bytenr,
+                           u64 parent, u64 root, u64 owner, u64 offset,
+                           u32 num_refs, int found_ref, u64 max_size)
+{
+       struct extent_record *rec;
+       struct data_backref *back;
+       struct cache_extent *cache;
+       int ret;
 
-       if (num_bytes % root->sectorsize)
-               return -EINVAL;
+       cache = lookup_cache_extent(extent_cache, bytenr, 1);
+       if (!cache) {
+               struct extent_record tmpl;
 
-       data = malloc(num_bytes);
-       if (!data)
-               return -ENOMEM;
+               memset(&tmpl, 0, sizeof(tmpl));
+               tmpl.start = bytenr;
+               tmpl.nr = 1;
+               tmpl.max_size = max_size;
 
-       while (offset < num_bytes) {
-               mirror = 0;
-again:
-               read_len = num_bytes - offset;
-               /* read as much space once a time */
-               ret = read_extent_data(root, data + offset,
-                               bytenr + offset, &read_len, mirror);
+               ret = add_extent_rec_nolookup(extent_cache, &tmpl);
                if (ret)
-                       goto out;
-               data_checked = 0;
-               /* verify every 4k data's checksum */
-               while (data_checked < read_len) {
-                       csum = ~(u32)0;
-                       tmp = offset + data_checked;
+                       return ret;
 
-                       csum = btrfs_csum_data(NULL, (char *)data + tmp,
-                                              csum, root->sectorsize);
-                       btrfs_csum_final(csum, (char *)&csum);
+               cache = lookup_cache_extent(extent_cache, bytenr, 1);
+               if (!cache)
+                       abort();
+       }
 
-                       csum_offset = leaf_offset +
-                                tmp / root->sectorsize * csum_size;
-                       read_extent_buffer(eb, (char *)&csum_expected,
-                                          csum_offset, csum_size);
-                       /* try another mirror */
-                       if (csum != csum_expected) {
-                               fprintf(stderr, "mirror %d bytenr %llu csum %u expected csum %u\n",
-                                               mirror, bytenr + tmp,
-                                               csum, csum_expected);
-                               num_copies = btrfs_num_copies(
-                                               &root->fs_info->mapping_tree,
-                                               bytenr, num_bytes);
-                               if (mirror < num_copies - 1) {
-                                       mirror += 1;
-                                       goto again;
-                               }
-                       }
-                       data_checked += root->sectorsize;
+       rec = container_of(cache, struct extent_record, cache);
+       if (rec->max_size < max_size)
+               rec->max_size = max_size;
+
+       /*
+        * If found_ref is set then max_size is the real size and must match the
+        * existing refs.  So if we have already found a ref then we need to
+        * make sure that this ref matches the existing one, otherwise we need
+        * to add a new backref so we can notice that the backrefs don't match
+        * and we need to figure out who is telling the truth.  This is to
+        * account for that awful fsync bug I introduced where we'd end up with
+        * a btrfs_file_extent_item that would have its length include multiple
+        * prealloc extents or point inside of a prealloc extent.
+        */
+       back = find_data_backref(rec, parent, root, owner, offset, found_ref,
+                                bytenr, max_size);
+       if (!back) {
+               back = alloc_data_backref(rec, parent, root, owner, offset,
+                                         max_size);
+               BUG_ON(!back);
+       }
+
+       if (found_ref) {
+               BUG_ON(num_refs != 1);
+               if (back->node.found_ref)
+                       BUG_ON(back->bytes != max_size);
+               back->node.found_ref = 1;
+               back->found_ref += 1;
+               back->bytes = max_size;
+               back->disk_bytenr = bytenr;
+               rec->refs += 1;
+               rec->content_checked = 1;
+               rec->owner_ref_checked = 1;
+       } else {
+               if (back->node.found_extent_tree) {
+                       fprintf(stderr, "Extent back ref already exists "
+                               "for %llu parent %llu root %llu "
+                               "owner %llu offset %llu num_refs %lu\n",
+                               (unsigned long long)bytenr,
+                               (unsigned long long)parent,
+                               (unsigned long long)root,
+                               (unsigned long long)owner,
+                               (unsigned long long)offset,
+                               (unsigned long)num_refs);
                }
-               offset += read_len;
+               back->num_refs = num_refs;
+               back->node.found_extent_tree = 1;
        }
-out:
-       free(data);
-       return ret;
+       maybe_free_extent_rec(extent_cache, rec);
+       return 0;
 }
 
-static int check_extent_exists(struct btrfs_root *root, u64 bytenr,
-                              u64 num_bytes)
+static int add_pending(struct cache_tree *pending,
+                      struct cache_tree *seen, u64 bytenr, u32 size)
 {
-       struct btrfs_path *path;
-       struct extent_buffer *leaf;
-       struct btrfs_key key;
        int ret;
+       ret = add_cache_extent(seen, bytenr, size);
+       if (ret)
+               return ret;
+       add_cache_extent(pending, bytenr, size);
+       return 0;
+}
 
-       path = btrfs_alloc_path();
-       if (!path) {
-               fprintf(stderr, "Error allocing path\n");
-               return -ENOMEM;
-       }
-
-       key.objectid = bytenr;
-       key.type = BTRFS_EXTENT_ITEM_KEY;
-       key.offset = (u64)-1;
+static int pick_next_pending(struct cache_tree *pending,
+                       struct cache_tree *reada,
+                       struct cache_tree *nodes,
+                       u64 last, struct block_info *bits, int bits_nr,
+                       int *reada_bits)
+{
+       unsigned long node_start = last;
+       struct cache_extent *cache;
+       int ret;
 
-again:
-       ret = btrfs_search_slot(NULL, root->fs_info->extent_root, &key, path,
-                               0, 0);
-       if (ret < 0) {
-               fprintf(stderr, "Error looking up extent record %d\n", ret);
-               btrfs_free_path(path);
-               return ret;
-       } else if (ret) {
-               if (path->slots[0] > 0) {
-                       path->slots[0]--;
-               } else {
-                       ret = btrfs_prev_leaf(root, path);
-                       if (ret < 0) {
-                               goto out;
-                       } else if (ret > 0) {
-                               ret = 0;
-                               goto out;
-                       }
-               }
+       cache = search_cache_extent(reada, 0);
+       if (cache) {
+               bits[0].start = cache->start;
+               bits[0].size = cache->size;
+               *reada_bits = 1;
+               return 1;
        }
+       *reada_bits = 0;
+       if (node_start > 32768)
+               node_start -= 32768;
 
-       btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+       cache = search_cache_extent(nodes, node_start);
+       if (!cache)
+               cache = search_cache_extent(nodes, 0);
 
-       /*
-        * Block group items come before extent items if they have the same
-        * bytenr, so walk back one more just in case.  Dear future traveler,
-        * first congrats on mastering time travel.  Now if it's not too much
-        * trouble could you go back to 2006 and tell Chris to make the
-        * BLOCK_GROUP_ITEM_KEY (and BTRFS_*_REF_KEY) lower than the
-        * EXTENT_ITEM_KEY please?
-        */
-       while (key.type > BTRFS_EXTENT_ITEM_KEY) {
-               if (path->slots[0] > 0) {
-                       path->slots[0]--;
-               } else {
-                       ret = btrfs_prev_leaf(root, path);
-                       if (ret < 0) {
-                               goto out;
-                       } else if (ret > 0) {
-                               ret = 0;
-                               goto out;
-                       }
-               }
-               btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+       if (!cache) {
+                cache = search_cache_extent(pending, 0);
+                if (!cache)
+                        return 0;
+                ret = 0;
+                do {
+                        bits[ret].start = cache->start;
+                        bits[ret].size = cache->size;
+                        cache = next_cache_extent(cache);
+                        ret++;
+                } while (cache && ret < bits_nr);
+                return ret;
        }
 
-       while (num_bytes) {
-               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-                       ret = btrfs_next_leaf(root, path);
-                       if (ret < 0) {
-                               fprintf(stderr, "Error going to next leaf "
-                                       "%d\n", ret);
-                               btrfs_free_path(path);
-                               return ret;
-                       } else if (ret) {
-                               break;
-                       }
-               }
-               leaf = path->nodes[0];
-               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
-               if (key.type != BTRFS_EXTENT_ITEM_KEY) {
-                       path->slots[0]++;
-                       continue;
-               }
-               if (key.objectid + key.offset < bytenr) {
-                       path->slots[0]++;
-                       continue;
-               }
-               if (key.objectid > bytenr + num_bytes)
-                       break;
+       ret = 0;
+       do {
+               bits[ret].start = cache->start;
+               bits[ret].size = cache->size;
+               cache = next_cache_extent(cache);
+               ret++;
+       } while (cache && ret < bits_nr);
 
-               if (key.objectid == bytenr) {
-                       if (key.offset >= num_bytes) {
-                               num_bytes = 0;
+       if (bits_nr - ret > 8) {
+               u64 lookup = bits[0].start + bits[0].size;
+               struct cache_extent *next;
+               next = search_cache_extent(pending, lookup);
+               while(next) {
+                       if (next->start - lookup > 32768)
                                break;
-                       }
-                       num_bytes -= key.offset;
-                       bytenr += key.offset;
-               } else if (key.objectid < bytenr) {
-                       if (key.objectid + key.offset >= bytenr + num_bytes) {
-                               num_bytes = 0;
+                       bits[ret].start = next->start;
+                       bits[ret].size = next->size;
+                       lookup = next->start + next->size;
+                       ret++;
+                       if (ret == bits_nr)
+                               break;
+                       next = next_cache_extent(next);
+                       if (!next)
                                break;
-                       }
-                       num_bytes = (bytenr + num_bytes) -
-                               (key.objectid + key.offset);
-                       bytenr = key.objectid + key.offset;
-               } else {
-                       if (key.objectid + key.offset < bytenr + num_bytes) {
-                               u64 new_start = key.objectid + key.offset;
-                               u64 new_bytes = bytenr + num_bytes - new_start;
-
-                               /*
-                                * Weird case, the extent is in the middle of
-                                * our range, we'll have to search one side
-                                * and then the other.  Not sure if this happens
-                                * in real life, but no harm in coding it up
-                                * anyway just in case.
-                                */
-                               btrfs_release_path(path);
-                               ret = check_extent_exists(root, new_start,
-                                                         new_bytes);
-                               if (ret) {
-                                       fprintf(stderr, "Right section didn't "
-                                               "have a record\n");
-                                       break;
-                               }
-                               num_bytes = key.objectid - bytenr;
-                               goto again;
-                       }
-                       num_bytes = key.objectid - bytenr;
                }
-               path->slots[0]++;
-       }
-       ret = 0;
-
-out:
-       if (num_bytes && !ret) {
-               fprintf(stderr, "There are no extents for csum range "
-                       "%Lu-%Lu\n", bytenr, bytenr+num_bytes);
-               ret = 1;
        }
-
-       btrfs_free_path(path);
        return ret;
 }
 
-static int check_csums(struct btrfs_root *root)
+static void free_chunk_record(struct cache_extent *cache)
 {
-       struct btrfs_path *path;
-       struct extent_buffer *leaf;
-       struct btrfs_key key;
-       u64 offset = 0, num_bytes = 0;
-       u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
-       int errors = 0;
-       int ret;
-       u64 data_len;
-       unsigned long leaf_offset;
-
-       root = root->fs_info->csum_root;
-       if (!extent_buffer_uptodate(root->node)) {
-               fprintf(stderr, "No valid csum tree found\n");
-               return -ENOENT;
-       }
+       struct chunk_record *rec;
 
-       key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
-       key.type = BTRFS_EXTENT_CSUM_KEY;
-       key.offset = 0;
+       rec = container_of(cache, struct chunk_record, cache);
+       list_del_init(&rec->list);
+       list_del_init(&rec->dextents);
+       free(rec);
+}
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
+void free_chunk_cache_tree(struct cache_tree *chunk_cache)
+{
+       cache_tree_free_extents(chunk_cache, free_chunk_record);
+}
 
-       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-       if (ret < 0) {
-               fprintf(stderr, "Error searching csum tree %d\n", ret);
-               btrfs_free_path(path);
-               return ret;
-       }
+static void free_device_record(struct rb_node *node)
+{
+       struct device_record *rec;
 
-       if (ret > 0 && path->slots[0])
-               path->slots[0]--;
-       ret = 0;
+       rec = container_of(node, struct device_record, node);
+       free(rec);
+}
 
-       while (1) {
-               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-                       ret = btrfs_next_leaf(root, path);
-                       if (ret < 0) {
-                               fprintf(stderr, "Error going to next leaf "
-                                       "%d\n", ret);
-                               break;
-                       }
-                       if (ret)
-                               break;
-               }
-               leaf = path->nodes[0];
+FREE_RB_BASED_TREE(device_cache, free_device_record);
 
-               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
-               if (key.type != BTRFS_EXTENT_CSUM_KEY) {
-                       path->slots[0]++;
-                       continue;
-               }
+int insert_block_group_record(struct block_group_tree *tree,
+                             struct block_group_record *bg_rec)
+{
+       int ret;
 
-               data_len = (btrfs_item_size_nr(leaf, path->slots[0]) /
-                             csum_size) * root->sectorsize;
-               if (!check_data_csum)
-                       goto skip_csum_check;
-               leaf_offset = btrfs_item_ptr_offset(leaf, path->slots[0]);
-               ret = check_extent_csums(root, key.offset, data_len,
-                                        leaf_offset, leaf);
-               if (ret)
-                       break;
-skip_csum_check:
-               if (!num_bytes) {
-                       offset = key.offset;
-               } else if (key.offset != offset + num_bytes) {
-                       ret = check_extent_exists(root, offset, num_bytes);
-                       if (ret) {
-                               fprintf(stderr, "Csum exists for %Lu-%Lu but "
-                                       "there is no extent record\n",
-                                       offset, offset+num_bytes);
-                               errors++;
-                       }
-                       offset = key.offset;
-                       num_bytes = 0;
-               }
-               num_bytes += data_len;
-               path->slots[0]++;
-       }
+       ret = insert_cache_extent(&tree->tree, &bg_rec->cache);
+       if (ret)
+               return ret;
 
-       btrfs_free_path(path);
-       return errors;
+       list_add_tail(&bg_rec->list, &tree->block_groups);
+       return 0;
 }
 
-static int is_dropped_key(struct btrfs_key *key,
-                         struct btrfs_key *drop_key) {
-       if (key->objectid < drop_key->objectid)
-               return 1;
-       else if (key->objectid == drop_key->objectid) {
-               if (key->type < drop_key->type)
-                       return 1;
-               else if (key->type == drop_key->type) {
-                       if (key->offset < drop_key->offset)
-                               return 1;
-               }
-       }
-       return 0;
+static void free_block_group_record(struct cache_extent *cache)
+{
+       struct block_group_record *rec;
+
+       rec = container_of(cache, struct block_group_record, cache);
+       list_del_init(&rec->list);
+       free(rec);
 }
 
-/*
- * Here are the rules for FULL_BACKREF.
- *
- * 1) If BTRFS_HEADER_FLAG_RELOC is set then we have FULL_BACKREF set.
- * 2) If btrfs_header_owner(buf) no longer points to buf then we have
- *     FULL_BACKREF set.
- * 3) We cow'ed the block walking down a reloc tree.  This is impossible to tell
- *    if it happened after the relocation occurred since we'll have dropped the
- *    reloc root, so it's entirely possible to have FULL_BACKREF set on buf and
- *    have no real way to know for sure.
- *
- * We process the blocks one root at a time, and we start from the lowest root
- * objectid and go to the highest.  So we can just lookup the owner backref for
- * the record and if we don't find it then we know it doesn't exist and we have
- * a FULL BACKREF.
- *
- * FIXME: if we ever start reclaiming root objectid's then we need to fix this
- * assumption and simply indicate that we _think_ that the FULL BACKREF needs to
- * be set or not and then we can check later once we've gathered all the refs.
- */
-static int calc_extent_flag(struct btrfs_root *root,
-                          struct cache_tree *extent_cache,
-                          struct extent_buffer *buf,
-                          struct root_item_record *ri,
-                          u64 *flags)
+void free_block_group_tree(struct block_group_tree *tree)
 {
-       struct extent_record *rec;
-       struct cache_extent *cache;
-       struct tree_backref *tback;
-       u64 owner = 0;
+       cache_tree_free_extents(&tree->tree, free_block_group_record);
+}
 
-       cache = lookup_cache_extent(extent_cache, buf->start, 1);
-       /* we have added this extent before */
-       BUG_ON(!cache);
-       rec = container_of(cache, struct extent_record, cache);
+int insert_device_extent_record(struct device_extent_tree *tree,
+                               struct device_extent_record *de_rec)
+{
+       int ret;
 
        /*
-        * Except file/reloc tree, we can not have
-        * FULL BACKREF MODE
-        */
-       if (ri->objectid < BTRFS_FIRST_FREE_OBJECTID)
-               goto normal;
-       /*
-        * root node
+        * Device extent is a bit different from the other extents, because
+        * the extents which belong to the different devices may have the
+        * same start and size, so we need use the special extent cache
+        * search/insert functions.
         */
-       if (buf->start == ri->bytenr)
-               goto normal;
+       ret = insert_cache_extent2(&tree->tree, &de_rec->cache);
+       if (ret)
+               return ret;
 
-       if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))
-               goto full_backref;
+       list_add_tail(&de_rec->chunk_list, &tree->no_chunk_orphans);
+       list_add_tail(&de_rec->device_list, &tree->no_device_orphans);
+       return 0;
+}
 
-       owner = btrfs_header_owner(buf);
-       if (owner == ri->objectid)
-               goto normal;
+static void free_device_extent_record(struct cache_extent *cache)
+{
+       struct device_extent_record *rec;
 
-       tback = find_tree_backref(rec, 0, owner);
-       if (!tback)
-               goto full_backref;
-normal:
-       *flags = 0;
-       if (rec->flag_block_full_backref != -1 &&
-           rec->flag_block_full_backref != 0)
-               rec->bad_full_backref = 1;
-       return 0;
-full_backref:
-       *flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
-       if (rec->flag_block_full_backref != -1 &&
-           rec->flag_block_full_backref != 1)
-               rec->bad_full_backref = 1;
-       return 0;
+       rec = container_of(cache, struct device_extent_record, cache);
+       if (!list_empty(&rec->chunk_list))
+               list_del_init(&rec->chunk_list);
+       if (!list_empty(&rec->device_list))
+               list_del_init(&rec->device_list);
+       free(rec);
 }
 
-static int run_next_block(struct btrfs_root *root,
-                         struct block_info *bits,
-                         int bits_nr,
-                         u64 *last,
-                         struct cache_tree *pending,
-                         struct cache_tree *seen,
-                         struct cache_tree *reada,
-                         struct cache_tree *nodes,
-                         struct cache_tree *extent_cache,
-                         struct cache_tree *chunk_cache,
-                         struct rb_root *dev_cache,
-                         struct block_group_tree *block_group_cache,
-                         struct device_extent_tree *dev_extent_cache,
-                         struct root_item_record *ri)
+void free_device_extent_tree(struct device_extent_tree *tree)
 {
-       struct extent_buffer *buf;
-       struct extent_record *rec = NULL;
-       u64 bytenr;
-       u32 size;
-       u64 parent;
-       u64 owner;
-       u64 flags;
-       u64 ptr;
-       u64 gen = 0;
-       int ret = 0;
-       int i;
-       int nritems;
+       cache_tree_free_extents(&tree->tree, free_device_extent_record);
+}
+
+#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
+static int process_extent_ref_v0(struct cache_tree *extent_cache,
+                                struct extent_buffer *leaf, int slot)
+{
+       struct btrfs_extent_ref_v0 *ref0;
        struct btrfs_key key;
-       struct cache_extent *cache;
-       int reada_bits;
+       int ret;
 
-       nritems = pick_next_pending(pending, reada, nodes, *last, bits,
-                                   bits_nr, &reada_bits);
-       if (nritems == 0)
-               return 1;
+       btrfs_item_key_to_cpu(leaf, &key, slot);
+       ref0 = btrfs_item_ptr(leaf, slot, struct btrfs_extent_ref_v0);
+       if (btrfs_ref_objectid_v0(leaf, ref0) < BTRFS_FIRST_FREE_OBJECTID) {
+               ret = add_tree_backref(extent_cache, key.objectid, key.offset,
+                               0, 0);
+       } else {
+               ret = add_data_backref(extent_cache, key.objectid, key.offset,
+                               0, 0, 0, btrfs_ref_count_v0(leaf, ref0), 0, 0);
+       }
+       return ret;
+}
+#endif
 
-       if (!reada_bits) {
-               for(i = 0; i < nritems; i++) {
-                       ret = add_cache_extent(reada, bits[i].start,
-                                              bits[i].size);
-                       if (ret == -EEXIST)
-                               continue;
+struct chunk_record *btrfs_new_chunk_record(struct extent_buffer *leaf,
+                                           struct btrfs_key *key,
+                                           int slot)
+{
+       struct btrfs_chunk *ptr;
+       struct chunk_record *rec;
+       int num_stripes, i;
 
-                       /* fixme, get the parent transid */
-                       readahead_tree_block(root, bits[i].start,
-                                            bits[i].size, 0);
-               }
+       ptr = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
+       num_stripes = btrfs_chunk_num_stripes(leaf, ptr);
+
+       rec = calloc(1, btrfs_chunk_record_size(num_stripes));
+       if (!rec) {
+               fprintf(stderr, "memory allocation failed\n");
+               exit(-1);
        }
-       *last = bits[0].start;
-       bytenr = bits[0].start;
-       size = bits[0].size;
 
-       cache = lookup_cache_extent(pending, bytenr, size);
-       if (cache) {
-               remove_cache_extent(pending, cache);
-               free(cache);
+       INIT_LIST_HEAD(&rec->list);
+       INIT_LIST_HEAD(&rec->dextents);
+       rec->bg_rec = NULL;
+
+       rec->cache.start = key->offset;
+       rec->cache.size = btrfs_chunk_length(leaf, ptr);
+
+       rec->generation = btrfs_header_generation(leaf);
+
+       rec->objectid = key->objectid;
+       rec->type = key->type;
+       rec->offset = key->offset;
+
+       rec->length = rec->cache.size;
+       rec->owner = btrfs_chunk_owner(leaf, ptr);
+       rec->stripe_len = btrfs_chunk_stripe_len(leaf, ptr);
+       rec->type_flags = btrfs_chunk_type(leaf, ptr);
+       rec->io_width = btrfs_chunk_io_width(leaf, ptr);
+       rec->io_align = btrfs_chunk_io_align(leaf, ptr);
+       rec->sector_size = btrfs_chunk_sector_size(leaf, ptr);
+       rec->num_stripes = num_stripes;
+       rec->sub_stripes = btrfs_chunk_sub_stripes(leaf, ptr);
+
+       for (i = 0; i < rec->num_stripes; ++i) {
+               rec->stripes[i].devid =
+                       btrfs_stripe_devid_nr(leaf, ptr, i);
+               rec->stripes[i].offset =
+                       btrfs_stripe_offset_nr(leaf, ptr, i);
+               read_extent_buffer(leaf, rec->stripes[i].dev_uuid,
+                               (unsigned long)btrfs_stripe_dev_uuid_nr(ptr, i),
+                               BTRFS_UUID_SIZE);
        }
-       cache = lookup_cache_extent(reada, bytenr, size);
-       if (cache) {
-               remove_cache_extent(reada, cache);
-               free(cache);
+
+       return rec;
+}
+
+static int process_chunk_item(struct cache_tree *chunk_cache,
+                             struct btrfs_key *key, struct extent_buffer *eb,
+                             int slot)
+{
+       struct chunk_record *rec;
+       struct btrfs_chunk *chunk;
+       int ret = 0;
+
+       chunk = btrfs_item_ptr(eb, slot, struct btrfs_chunk);
+       /*
+        * Do extra check for this chunk item,
+        *
+        * It's still possible one can craft a leaf with CHUNK_ITEM, with
+        * wrong onwer(3) out of chunk tree, to pass both chunk tree check
+        * and owner<->key_type check.
+        */
+       ret = btrfs_check_chunk_valid(global_info->tree_root, eb, chunk, slot,
+                                     key->offset);
+       if (ret < 0) {
+               error("chunk(%llu, %llu) is not valid, ignore it",
+                     key->offset, btrfs_chunk_length(eb, chunk));
+               return 0;
        }
-       cache = lookup_cache_extent(nodes, bytenr, size);
-       if (cache) {
-               remove_cache_extent(nodes, cache);
-               free(cache);
+       rec = btrfs_new_chunk_record(eb, key, slot);
+       ret = insert_cache_extent(chunk_cache, &rec->cache);
+       if (ret) {
+               fprintf(stderr, "Chunk[%llu, %llu] existed.\n",
+                       rec->offset, rec->length);
+               free(rec);
        }
-       cache = lookup_cache_extent(extent_cache, bytenr, size);
-       if (cache) {
-               rec = container_of(cache, struct extent_record, cache);
-               gen = rec->parent_generation;
+
+       return ret;
+}
+
+static int process_device_item(struct rb_root *dev_cache,
+               struct btrfs_key *key, struct extent_buffer *eb, int slot)
+{
+       struct btrfs_dev_item *ptr;
+       struct device_record *rec;
+       int ret = 0;
+
+       ptr = btrfs_item_ptr(eb,
+               slot, struct btrfs_dev_item);
+
+       rec = malloc(sizeof(*rec));
+       if (!rec) {
+               fprintf(stderr, "memory allocation failed\n");
+               return -ENOMEM;
        }
 
-       /* fixme, get the real parent transid */
-       buf = read_tree_block(root, bytenr, size, gen);
-       if (!extent_buffer_uptodate(buf)) {
-               record_bad_block_io(root->fs_info,
-                                   extent_cache, bytenr, size);
-               goto out;
+       rec->devid = key->offset;
+       rec->generation = btrfs_header_generation(eb);
+
+       rec->objectid = key->objectid;
+       rec->type = key->type;
+       rec->offset = key->offset;
+
+       rec->devid = btrfs_device_id(eb, ptr);
+       rec->total_byte = btrfs_device_total_bytes(eb, ptr);
+       rec->byte_used = btrfs_device_bytes_used(eb, ptr);
+
+       ret = rb_insert(dev_cache, &rec->node, device_record_compare);
+       if (ret) {
+               fprintf(stderr, "Device[%llu] existed.\n", rec->devid);
+               free(rec);
        }
 
-       nritems = btrfs_header_nritems(buf);
+       return ret;
+}
 
-       flags = 0;
-       if (!init_extent_tree) {
-               ret = btrfs_lookup_extent_info(NULL, root, bytenr,
-                                      btrfs_header_level(buf), 1, NULL,
-                                      &flags);
-               if (ret < 0) {
-                       ret = calc_extent_flag(root, extent_cache, buf, ri, &flags);
-                       if (ret < 0) {
-                               fprintf(stderr, "Couldn't calc extent flags\n");
-                               flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
-                       }
-               }
-       } else {
-               flags = 0;
-               ret = calc_extent_flag(root, extent_cache, buf, ri, &flags);
-               if (ret < 0) {
-                       fprintf(stderr, "Couldn't calc extent flags\n");
-                       flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
-               }
+struct block_group_record *
+btrfs_new_block_group_record(struct extent_buffer *leaf, struct btrfs_key *key,
+                            int slot)
+{
+       struct btrfs_block_group_item *ptr;
+       struct block_group_record *rec;
+
+       rec = calloc(1, sizeof(*rec));
+       if (!rec) {
+               fprintf(stderr, "memory allocation failed\n");
+               exit(-1);
        }
 
-       if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
-               if (ri != NULL &&
+       rec->cache.start = key->objectid;
+       rec->cache.size = key->offset;
+
+       rec->generation = btrfs_header_generation(leaf);
+
+       rec->objectid = key->objectid;
+       rec->type = key->type;
+       rec->offset = key->offset;
+
+       ptr = btrfs_item_ptr(leaf, slot, struct btrfs_block_group_item);
+       rec->flags = btrfs_disk_block_group_flags(leaf, ptr);
+
+       INIT_LIST_HEAD(&rec->list);
+
+       return rec;
+}
+
+static int process_block_group_item(struct block_group_tree *block_group_cache,
+                                   struct btrfs_key *key,
+                                   struct extent_buffer *eb, int slot)
+{
+       struct block_group_record *rec;
+       int ret = 0;
+
+       rec = btrfs_new_block_group_record(eb, key, slot);
+       ret = insert_block_group_record(block_group_cache, rec);
+       if (ret) {
+               fprintf(stderr, "Block Group[%llu, %llu] existed.\n",
+                       rec->objectid, rec->offset);
+               free(rec);
+       }
+
+       return ret;
+}
+
+struct device_extent_record *
+btrfs_new_device_extent_record(struct extent_buffer *leaf,
+                              struct btrfs_key *key, int slot)
+{
+       struct device_extent_record *rec;
+       struct btrfs_dev_extent *ptr;
+
+       rec = calloc(1, sizeof(*rec));
+       if (!rec) {
+               fprintf(stderr, "memory allocation failed\n");
+               exit(-1);
+       }
+
+       rec->cache.objectid = key->objectid;
+       rec->cache.start = key->offset;
+
+       rec->generation = btrfs_header_generation(leaf);
+
+       rec->objectid = key->objectid;
+       rec->type = key->type;
+       rec->offset = key->offset;
+
+       ptr = btrfs_item_ptr(leaf, slot, struct btrfs_dev_extent);
+       rec->chunk_objecteid =
+               btrfs_dev_extent_chunk_objectid(leaf, ptr);
+       rec->chunk_offset =
+               btrfs_dev_extent_chunk_offset(leaf, ptr);
+       rec->length = btrfs_dev_extent_length(leaf, ptr);
+       rec->cache.size = rec->length;
+
+       INIT_LIST_HEAD(&rec->chunk_list);
+       INIT_LIST_HEAD(&rec->device_list);
+
+       return rec;
+}
+
+static int
+process_device_extent_item(struct device_extent_tree *dev_extent_cache,
+                          struct btrfs_key *key, struct extent_buffer *eb,
+                          int slot)
+{
+       struct device_extent_record *rec;
+       int ret;
+
+       rec = btrfs_new_device_extent_record(eb, key, slot);
+       ret = insert_device_extent_record(dev_extent_cache, rec);
+       if (ret) {
+               fprintf(stderr,
+                       "Device extent[%llu, %llu, %llu] existed.\n",
+                       rec->objectid, rec->offset, rec->length);
+               free(rec);
+       }
+
+       return ret;
+}
+
+static int process_extent_item(struct btrfs_root *root,
+                              struct cache_tree *extent_cache,
+                              struct extent_buffer *eb, int slot)
+{
+       struct btrfs_extent_item *ei;
+       struct btrfs_extent_inline_ref *iref;
+       struct btrfs_extent_data_ref *dref;
+       struct btrfs_shared_data_ref *sref;
+       struct btrfs_key key;
+       struct extent_record tmpl;
+       unsigned long end;
+       unsigned long ptr;
+       int ret;
+       int type;
+       u32 item_size = btrfs_item_size_nr(eb, slot);
+       u64 refs = 0;
+       u64 offset;
+       u64 num_bytes;
+       int metadata = 0;
+
+       btrfs_item_key_to_cpu(eb, &key, slot);
+
+       if (key.type == BTRFS_METADATA_ITEM_KEY) {
+               metadata = 1;
+               num_bytes = root->nodesize;
+       } else {
+               num_bytes = key.offset;
+       }
+
+       if (!IS_ALIGNED(key.objectid, root->sectorsize)) {
+               error("ignoring invalid extent, bytenr %llu is not aligned to %u",
+                     key.objectid, root->sectorsize);
+               return -EIO;
+       }
+       if (item_size < sizeof(*ei)) {
+#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
+               struct btrfs_extent_item_v0 *ei0;
+               BUG_ON(item_size != sizeof(*ei0));
+               ei0 = btrfs_item_ptr(eb, slot, struct btrfs_extent_item_v0);
+               refs = btrfs_extent_refs_v0(eb, ei0);
+#else
+               BUG();
+#endif
+               memset(&tmpl, 0, sizeof(tmpl));
+               tmpl.start = key.objectid;
+               tmpl.nr = num_bytes;
+               tmpl.extent_item_refs = refs;
+               tmpl.metadata = metadata;
+               tmpl.found_rec = 1;
+               tmpl.max_size = num_bytes;
+
+               return add_extent_rec(extent_cache, &tmpl);
+       }
+
+       ei = btrfs_item_ptr(eb, slot, struct btrfs_extent_item);
+       refs = btrfs_extent_refs(eb, ei);
+       if (btrfs_extent_flags(eb, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+               metadata = 1;
+       else
+               metadata = 0;
+       if (metadata && num_bytes != root->nodesize) {
+               error("ignore invalid metadata extent, length %llu does not equal to %u",
+                     num_bytes, root->nodesize);
+               return -EIO;
+       }
+       if (!metadata && !IS_ALIGNED(num_bytes, root->sectorsize)) {
+               error("ignore invalid data extent, length %llu is not aligned to %u",
+                     num_bytes, root->sectorsize);
+               return -EIO;
+       }
+
+       memset(&tmpl, 0, sizeof(tmpl));
+       tmpl.start = key.objectid;
+       tmpl.nr = num_bytes;
+       tmpl.extent_item_refs = refs;
+       tmpl.metadata = metadata;
+       tmpl.found_rec = 1;
+       tmpl.max_size = num_bytes;
+       add_extent_rec(extent_cache, &tmpl);
+
+       ptr = (unsigned long)(ei + 1);
+       if (btrfs_extent_flags(eb, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK &&
+           key.type == BTRFS_EXTENT_ITEM_KEY)
+               ptr += sizeof(struct btrfs_tree_block_info);
+
+       end = (unsigned long)ei + item_size;
+       while (ptr < end) {
+               iref = (struct btrfs_extent_inline_ref *)ptr;
+               type = btrfs_extent_inline_ref_type(eb, iref);
+               offset = btrfs_extent_inline_ref_offset(eb, iref);
+               switch (type) {
+               case BTRFS_TREE_BLOCK_REF_KEY:
+                       ret = add_tree_backref(extent_cache, key.objectid,
+                                       0, offset, 0);
+                       if (ret < 0)
+                               error("add_tree_backref failed: %s",
+                                     strerror(-ret));
+                       break;
+               case BTRFS_SHARED_BLOCK_REF_KEY:
+                       ret = add_tree_backref(extent_cache, key.objectid,
+                                       offset, 0, 0);
+                       if (ret < 0)
+                               error("add_tree_backref failed: %s",
+                                     strerror(-ret));
+                       break;
+               case BTRFS_EXTENT_DATA_REF_KEY:
+                       dref = (struct btrfs_extent_data_ref *)(&iref->offset);
+                       add_data_backref(extent_cache, key.objectid, 0,
+                                       btrfs_extent_data_ref_root(eb, dref),
+                                       btrfs_extent_data_ref_objectid(eb,
+                                                                      dref),
+                                       btrfs_extent_data_ref_offset(eb, dref),
+                                       btrfs_extent_data_ref_count(eb, dref),
+                                       0, num_bytes);
+                       break;
+               case BTRFS_SHARED_DATA_REF_KEY:
+                       sref = (struct btrfs_shared_data_ref *)(iref + 1);
+                       add_data_backref(extent_cache, key.objectid, offset,
+                                       0, 0, 0,
+                                       btrfs_shared_data_ref_count(eb, sref),
+                                       0, num_bytes);
+                       break;
+               default:
+                       fprintf(stderr, "corrupt extent record: key %Lu %u %Lu\n",
+                               key.objectid, key.type, num_bytes);
+                       goto out;
+               }
+               ptr += btrfs_extent_inline_ref_size(type);
+       }
+       WARN_ON(ptr > end);
+out:
+       return 0;
+}
+
+static int check_cache_range(struct btrfs_root *root,
+                            struct btrfs_block_group_cache *cache,
+                            u64 offset, u64 bytes)
+{
+       struct btrfs_free_space *entry;
+       u64 *logical;
+       u64 bytenr;
+       int stripe_len;
+       int i, nr, ret;
+
+       for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
+               bytenr = btrfs_sb_offset(i);
+               ret = btrfs_rmap_block(&root->fs_info->mapping_tree,
+                                      cache->key.objectid, bytenr, 0,
+                                      &logical, &nr, &stripe_len);
+               if (ret)
+                       return ret;
+
+               while (nr--) {
+                       if (logical[nr] + stripe_len <= offset)
+                               continue;
+                       if (offset + bytes <= logical[nr])
+                               continue;
+                       if (logical[nr] == offset) {
+                               if (stripe_len >= bytes) {
+                                       free(logical);
+                                       return 0;
+                               }
+                               bytes -= stripe_len;
+                               offset += stripe_len;
+                       } else if (logical[nr] < offset) {
+                               if (logical[nr] + stripe_len >=
+                                   offset + bytes) {
+                                       free(logical);
+                                       return 0;
+                               }
+                               bytes = (offset + bytes) -
+                                       (logical[nr] + stripe_len);
+                               offset = logical[nr] + stripe_len;
+                       } else {
+                               /*
+                                * Could be tricky, the super may land in the
+                                * middle of the area we're checking.  First
+                                * check the easiest case, it's at the end.
+                                */
+                               if (logical[nr] + stripe_len >=
+                                   bytes + offset) {
+                                       bytes = logical[nr] - offset;
+                                       continue;
+                               }
+
+                               /* Check the left side */
+                               ret = check_cache_range(root, cache,
+                                                       offset,
+                                                       logical[nr] - offset);
+                               if (ret) {
+                                       free(logical);
+                                       return ret;
+                               }
+
+                               /* Now we continue with the right side */
+                               bytes = (offset + bytes) -
+                                       (logical[nr] + stripe_len);
+                               offset = logical[nr] + stripe_len;
+                       }
+               }
+
+               free(logical);
+       }
+
+       entry = btrfs_find_free_space(cache->free_space_ctl, offset, bytes);
+       if (!entry) {
+               fprintf(stderr, "There is no free space entry for %Lu-%Lu\n",
+                       offset, offset+bytes);
+               return -EINVAL;
+       }
+
+       if (entry->offset != offset) {
+               fprintf(stderr, "Wanted offset %Lu, found %Lu\n", offset,
+                       entry->offset);
+               return -EINVAL;
+       }
+
+       if (entry->bytes != bytes) {
+               fprintf(stderr, "Wanted bytes %Lu, found %Lu for off %Lu\n",
+                       bytes, entry->bytes, offset);
+               return -EINVAL;
+       }
+
+       unlink_free_space(cache->free_space_ctl, entry);
+       free(entry);
+       return 0;
+}
+
+static int verify_space_cache(struct btrfs_root *root,
+                             struct btrfs_block_group_cache *cache)
+{
+       struct btrfs_path path;
+       struct extent_buffer *leaf;
+       struct btrfs_key key;
+       u64 last;
+       int ret = 0;
+
+       root = root->fs_info->extent_root;
+
+       last = max_t(u64, cache->key.objectid, BTRFS_SUPER_INFO_OFFSET);
+
+       btrfs_init_path(&path);
+       key.objectid = last;
+       key.offset = 0;
+       key.type = BTRFS_EXTENT_ITEM_KEY;
+       ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+       if (ret < 0)
+               goto out;
+       ret = 0;
+       while (1) {
+               if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
+                       ret = btrfs_next_leaf(root, &path);
+                       if (ret < 0)
+                               goto out;
+                       if (ret > 0) {
+                               ret = 0;
+                               break;
+                       }
+               }
+               leaf = path.nodes[0];
+               btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
+               if (key.objectid >= cache->key.offset + cache->key.objectid)
+                       break;
+               if (key.type != BTRFS_EXTENT_ITEM_KEY &&
+                   key.type != BTRFS_METADATA_ITEM_KEY) {
+                       path.slots[0]++;
+                       continue;
+               }
+
+               if (last == key.objectid) {
+                       if (key.type == BTRFS_EXTENT_ITEM_KEY)
+                               last = key.objectid + key.offset;
+                       else
+                               last = key.objectid + root->nodesize;
+                       path.slots[0]++;
+                       continue;
+               }
+
+               ret = check_cache_range(root, cache, last,
+                                       key.objectid - last);
+               if (ret)
+                       break;
+               if (key.type == BTRFS_EXTENT_ITEM_KEY)
+                       last = key.objectid + key.offset;
+               else
+                       last = key.objectid + root->nodesize;
+               path.slots[0]++;
+       }
+
+       if (last < cache->key.objectid + cache->key.offset)
+               ret = check_cache_range(root, cache, last,
+                                       cache->key.objectid +
+                                       cache->key.offset - last);
+
+out:
+       btrfs_release_path(&path);
+
+       if (!ret &&
+           !RB_EMPTY_ROOT(&cache->free_space_ctl->free_space_offset)) {
+               fprintf(stderr, "There are still entries left in the space "
+                       "cache\n");
+               ret = -EINVAL;
+       }
+
+       return ret;
+}
+
+static int check_space_cache(struct btrfs_root *root)
+{
+       struct btrfs_block_group_cache *cache;
+       u64 start = BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE;
+       int ret;
+       int error = 0;
+
+       if (btrfs_super_cache_generation(root->fs_info->super_copy) != -1ULL &&
+           btrfs_super_generation(root->fs_info->super_copy) !=
+           btrfs_super_cache_generation(root->fs_info->super_copy)) {
+               printf("cache and super generation don't match, space cache "
+                      "will be invalidated\n");
+               return 0;
+       }
+
+       if (ctx.progress_enabled) {
+               ctx.tp = TASK_FREE_SPACE;
+               task_start(ctx.info);
+       }
+
+       while (1) {
+               cache = btrfs_lookup_first_block_group(root->fs_info, start);
+               if (!cache)
+                       break;
+
+               start = cache->key.objectid + cache->key.offset;
+               if (!cache->free_space_ctl) {
+                       if (btrfs_init_free_space_ctl(cache,
+                                                     root->sectorsize)) {
+                               ret = -ENOMEM;
+                               break;
+                       }
+               } else {
+                       btrfs_remove_free_space_cache(cache);
+               }
+
+               if (btrfs_fs_compat_ro(root->fs_info,
+                                      BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE)) {
+                       ret = exclude_super_stripes(root, cache);
+                       if (ret) {
+                               fprintf(stderr, "could not exclude super stripes: %s\n",
+                                       strerror(-ret));
+                               error++;
+                               continue;
+                       }
+                       ret = load_free_space_tree(root->fs_info, cache);
+                       free_excluded_extents(root, cache);
+                       if (ret < 0) {
+                               fprintf(stderr, "could not load free space tree: %s\n",
+                                       strerror(-ret));
+                               error++;
+                               continue;
+                       }
+                       error += ret;
+               } else {
+                       ret = load_free_space_cache(root->fs_info, cache);
+                       if (!ret)
+                               continue;
+               }
+
+               ret = verify_space_cache(root, cache);
+               if (ret) {
+                       fprintf(stderr, "cache appears valid but isn't %Lu\n",
+                               cache->key.objectid);
+                       error++;
+               }
+       }
+
+       task_stop(ctx.info);
+
+       return error ? -EINVAL : 0;
+}
+
+static int check_extent_csums(struct btrfs_root *root, u64 bytenr,
+                       u64 num_bytes, unsigned long leaf_offset,
+                       struct extent_buffer *eb) {
+
+       u64 offset = 0;
+       u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
+       char *data;
+       unsigned long csum_offset;
+       u32 csum;
+       u32 csum_expected;
+       u64 read_len;
+       u64 data_checked = 0;
+       u64 tmp;
+       int ret = 0;
+       int mirror;
+       int num_copies;
+
+       if (num_bytes % root->sectorsize)
+               return -EINVAL;
+
+       data = malloc(num_bytes);
+       if (!data)
+               return -ENOMEM;
+
+       while (offset < num_bytes) {
+               mirror = 0;
+again:
+               read_len = num_bytes - offset;
+               /* read as much space once a time */
+               ret = read_extent_data(root, data + offset,
+                               bytenr + offset, &read_len, mirror);
+               if (ret)
+                       goto out;
+               data_checked = 0;
+               /* verify every 4k data's checksum */
+               while (data_checked < read_len) {
+                       csum = ~(u32)0;
+                       tmp = offset + data_checked;
+
+                       csum = btrfs_csum_data(NULL, (char *)data + tmp,
+                                              csum, root->sectorsize);
+                       btrfs_csum_final(csum, (u8 *)&csum);
+
+                       csum_offset = leaf_offset +
+                                tmp / root->sectorsize * csum_size;
+                       read_extent_buffer(eb, (char *)&csum_expected,
+                                          csum_offset, csum_size);
+                       /* try another mirror */
+                       if (csum != csum_expected) {
+                               fprintf(stderr, "mirror %d bytenr %llu csum %u expected csum %u\n",
+                                               mirror, bytenr + tmp,
+                                               csum, csum_expected);
+                               num_copies = btrfs_num_copies(
+                                               &root->fs_info->mapping_tree,
+                                               bytenr, num_bytes);
+                               if (mirror < num_copies - 1) {
+                                       mirror += 1;
+                                       goto again;
+                               }
+                       }
+                       data_checked += root->sectorsize;
+               }
+               offset += read_len;
+       }
+out:
+       free(data);
+       return ret;
+}
+
+static int check_extent_exists(struct btrfs_root *root, u64 bytenr,
+                              u64 num_bytes)
+{
+       struct btrfs_path path;
+       struct extent_buffer *leaf;
+       struct btrfs_key key;
+       int ret;
+
+       btrfs_init_path(&path);
+       key.objectid = bytenr;
+       key.type = BTRFS_EXTENT_ITEM_KEY;
+       key.offset = (u64)-1;
+
+again:
+       ret = btrfs_search_slot(NULL, root->fs_info->extent_root, &key, &path,
+                               0, 0);
+       if (ret < 0) {
+               fprintf(stderr, "Error looking up extent record %d\n", ret);
+               btrfs_release_path(&path);
+               return ret;
+       } else if (ret) {
+               if (path.slots[0] > 0) {
+                       path.slots[0]--;
+               } else {
+                       ret = btrfs_prev_leaf(root, &path);
+                       if (ret < 0) {
+                               goto out;
+                       } else if (ret > 0) {
+                               ret = 0;
+                               goto out;
+                       }
+               }
+       }
+
+       btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+
+       /*
+        * Block group items come before extent items if they have the same
+        * bytenr, so walk back one more just in case.  Dear future traveller,
+        * first congrats on mastering time travel.  Now if it's not too much
+        * trouble could you go back to 2006 and tell Chris to make the
+        * BLOCK_GROUP_ITEM_KEY (and BTRFS_*_REF_KEY) lower than the
+        * EXTENT_ITEM_KEY please?
+        */
+       while (key.type > BTRFS_EXTENT_ITEM_KEY) {
+               if (path.slots[0] > 0) {
+                       path.slots[0]--;
+               } else {
+                       ret = btrfs_prev_leaf(root, &path);
+                       if (ret < 0) {
+                               goto out;
+                       } else if (ret > 0) {
+                               ret = 0;
+                               goto out;
+                       }
+               }
+               btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+       }
+
+       while (num_bytes) {
+               if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
+                       ret = btrfs_next_leaf(root, &path);
+                       if (ret < 0) {
+                               fprintf(stderr, "Error going to next leaf "
+                                       "%d\n", ret);
+                               btrfs_release_path(&path);
+                               return ret;
+                       } else if (ret) {
+                               break;
+                       }
+               }
+               leaf = path.nodes[0];
+               btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
+               if (key.type != BTRFS_EXTENT_ITEM_KEY) {
+                       path.slots[0]++;
+                       continue;
+               }
+               if (key.objectid + key.offset < bytenr) {
+                       path.slots[0]++;
+                       continue;
+               }
+               if (key.objectid > bytenr + num_bytes)
+                       break;
+
+               if (key.objectid == bytenr) {
+                       if (key.offset >= num_bytes) {
+                               num_bytes = 0;
+                               break;
+                       }
+                       num_bytes -= key.offset;
+                       bytenr += key.offset;
+               } else if (key.objectid < bytenr) {
+                       if (key.objectid + key.offset >= bytenr + num_bytes) {
+                               num_bytes = 0;
+                               break;
+                       }
+                       num_bytes = (bytenr + num_bytes) -
+                               (key.objectid + key.offset);
+                       bytenr = key.objectid + key.offset;
+               } else {
+                       if (key.objectid + key.offset < bytenr + num_bytes) {
+                               u64 new_start = key.objectid + key.offset;
+                               u64 new_bytes = bytenr + num_bytes - new_start;
+
+                               /*
+                                * Weird case, the extent is in the middle of
+                                * our range, we'll have to search one side
+                                * and then the other.  Not sure if this happens
+                                * in real life, but no harm in coding it up
+                                * anyway just in case.
+                                */
+                               btrfs_release_path(&path);
+                               ret = check_extent_exists(root, new_start,
+                                                         new_bytes);
+                               if (ret) {
+                                       fprintf(stderr, "Right section didn't "
+                                               "have a record\n");
+                                       break;
+                               }
+                               num_bytes = key.objectid - bytenr;
+                               goto again;
+                       }
+                       num_bytes = key.objectid - bytenr;
+               }
+               path.slots[0]++;
+       }
+       ret = 0;
+
+out:
+       if (num_bytes && !ret) {
+               fprintf(stderr, "There are no extents for csum range "
+                       "%Lu-%Lu\n", bytenr, bytenr+num_bytes);
+               ret = 1;
+       }
+
+       btrfs_release_path(&path);
+       return ret;
+}
+
+static int check_csums(struct btrfs_root *root)
+{
+       struct btrfs_path path;
+       struct extent_buffer *leaf;
+       struct btrfs_key key;
+       u64 offset = 0, num_bytes = 0;
+       u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
+       int errors = 0;
+       int ret;
+       u64 data_len;
+       unsigned long leaf_offset;
+
+       root = root->fs_info->csum_root;
+       if (!extent_buffer_uptodate(root->node)) {
+               fprintf(stderr, "No valid csum tree found\n");
+               return -ENOENT;
+       }
+
+       btrfs_init_path(&path);
+       key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+       key.type = BTRFS_EXTENT_CSUM_KEY;
+       key.offset = 0;
+       ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+       if (ret < 0) {
+               fprintf(stderr, "Error searching csum tree %d\n", ret);
+               btrfs_release_path(&path);
+               return ret;
+       }
+
+       if (ret > 0 && path.slots[0])
+               path.slots[0]--;
+       ret = 0;
+
+       while (1) {
+               if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
+                       ret = btrfs_next_leaf(root, &path);
+                       if (ret < 0) {
+                               fprintf(stderr, "Error going to next leaf "
+                                       "%d\n", ret);
+                               break;
+                       }
+                       if (ret)
+                               break;
+               }
+               leaf = path.nodes[0];
+
+               btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
+               if (key.type != BTRFS_EXTENT_CSUM_KEY) {
+                       path.slots[0]++;
+                       continue;
+               }
+
+               data_len = (btrfs_item_size_nr(leaf, path.slots[0]) /
+                             csum_size) * root->sectorsize;
+               if (!check_data_csum)
+                       goto skip_csum_check;
+               leaf_offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
+               ret = check_extent_csums(root, key.offset, data_len,
+                                        leaf_offset, leaf);
+               if (ret)
+                       break;
+skip_csum_check:
+               if (!num_bytes) {
+                       offset = key.offset;
+               } else if (key.offset != offset + num_bytes) {
+                       ret = check_extent_exists(root, offset, num_bytes);
+                       if (ret) {
+                               fprintf(stderr, "Csum exists for %Lu-%Lu but "
+                                       "there is no extent record\n",
+                                       offset, offset+num_bytes);
+                               errors++;
+                       }
+                       offset = key.offset;
+                       num_bytes = 0;
+               }
+               num_bytes += data_len;
+               path.slots[0]++;
+       }
+
+       btrfs_release_path(&path);
+       return errors;
+}
+
+static int is_dropped_key(struct btrfs_key *key,
+                         struct btrfs_key *drop_key) {
+       if (key->objectid < drop_key->objectid)
+               return 1;
+       else if (key->objectid == drop_key->objectid) {
+               if (key->type < drop_key->type)
+                       return 1;
+               else if (key->type == drop_key->type) {
+                       if (key->offset < drop_key->offset)
+                               return 1;
+               }
+       }
+       return 0;
+}
+
+/*
+ * Here are the rules for FULL_BACKREF.
+ *
+ * 1) If BTRFS_HEADER_FLAG_RELOC is set then we have FULL_BACKREF set.
+ * 2) If btrfs_header_owner(buf) no longer points to buf then we have
+ *     FULL_BACKREF set.
+ * 3) We cowed the block walking down a reloc tree.  This is impossible to tell
+ *    if it happened after the relocation occurred since we'll have dropped the
+ *    reloc root, so it's entirely possible to have FULL_BACKREF set on buf and
+ *    have no real way to know for sure.
+ *
+ * We process the blocks one root at a time, and we start from the lowest root
+ * objectid and go to the highest.  So we can just lookup the owner backref for
+ * the record and if we don't find it then we know it doesn't exist and we have
+ * a FULL BACKREF.
+ *
+ * FIXME: if we ever start reclaiming root objectid's then we need to fix this
+ * assumption and simply indicate that we _think_ that the FULL BACKREF needs to
+ * be set or not and then we can check later once we've gathered all the refs.
+ */
+static int calc_extent_flag(struct btrfs_root *root,
+                          struct cache_tree *extent_cache,
+                          struct extent_buffer *buf,
+                          struct root_item_record *ri,
+                          u64 *flags)
+{
+       struct extent_record *rec;
+       struct cache_extent *cache;
+       struct tree_backref *tback;
+       u64 owner = 0;
+
+       cache = lookup_cache_extent(extent_cache, buf->start, 1);
+       /* we have added this extent before */
+       if (!cache)
+               return -ENOENT;
+
+       rec = container_of(cache, struct extent_record, cache);
+
+       /*
+        * Except file/reloc tree, we can not have
+        * FULL BACKREF MODE
+        */
+       if (ri->objectid < BTRFS_FIRST_FREE_OBJECTID)
+               goto normal;
+       /*
+        * root node
+        */
+       if (buf->start == ri->bytenr)
+               goto normal;
+
+       if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))
+               goto full_backref;
+
+       owner = btrfs_header_owner(buf);
+       if (owner == ri->objectid)
+               goto normal;
+
+       tback = find_tree_backref(rec, 0, owner);
+       if (!tback)
+               goto full_backref;
+normal:
+       *flags = 0;
+       if (rec->flag_block_full_backref != FLAG_UNSET &&
+           rec->flag_block_full_backref != 0)
+               rec->bad_full_backref = 1;
+       return 0;
+full_backref:
+       *flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
+       if (rec->flag_block_full_backref != FLAG_UNSET &&
+           rec->flag_block_full_backref != 1)
+               rec->bad_full_backref = 1;
+       return 0;
+}
+
+static void report_mismatch_key_root(u8 key_type, u64 rootid)
+{
+       fprintf(stderr, "Invalid key type(");
+       print_key_type(stderr, 0, key_type);
+       fprintf(stderr, ") found in root(");
+       print_objectid(stderr, rootid, 0);
+       fprintf(stderr, ")\n");
+}
+
+/*
+ * Check if the key is valid with its extent buffer.
+ *
+ * This is a early check in case invalid key exists in a extent buffer
+ * This is not comprehensive yet, but should prevent wrong key/item passed
+ * further
+ */
+static int check_type_with_root(u64 rootid, u8 key_type)
+{
+       switch (key_type) {
+       /* Only valid in chunk tree */
+       case BTRFS_DEV_ITEM_KEY:
+       case BTRFS_CHUNK_ITEM_KEY:
+               if (rootid != BTRFS_CHUNK_TREE_OBJECTID)
+                       goto err;
+               break;
+       /* valid in csum and log tree */
+       case BTRFS_CSUM_TREE_OBJECTID:
+               if (!(rootid == BTRFS_TREE_LOG_OBJECTID ||
+                     is_fstree(rootid)))
+                       goto err;
+               break;
+       case BTRFS_EXTENT_ITEM_KEY:
+       case BTRFS_METADATA_ITEM_KEY:
+       case BTRFS_BLOCK_GROUP_ITEM_KEY:
+               if (rootid != BTRFS_EXTENT_TREE_OBJECTID)
+                       goto err;
+               break;
+       case BTRFS_ROOT_ITEM_KEY:
+               if (rootid != BTRFS_ROOT_TREE_OBJECTID)
+                       goto err;
+               break;
+       case BTRFS_DEV_EXTENT_KEY:
+               if (rootid != BTRFS_DEV_TREE_OBJECTID)
+                       goto err;
+               break;
+       }
+       return 0;
+err:
+       report_mismatch_key_root(key_type, rootid);
+       return -EINVAL;
+}
+
+static int run_next_block(struct btrfs_root *root,
+                         struct block_info *bits,
+                         int bits_nr,
+                         u64 *last,
+                         struct cache_tree *pending,
+                         struct cache_tree *seen,
+                         struct cache_tree *reada,
+                         struct cache_tree *nodes,
+                         struct cache_tree *extent_cache,
+                         struct cache_tree *chunk_cache,
+                         struct rb_root *dev_cache,
+                         struct block_group_tree *block_group_cache,
+                         struct device_extent_tree *dev_extent_cache,
+                         struct root_item_record *ri)
+{
+       struct extent_buffer *buf;
+       struct extent_record *rec = NULL;
+       u64 bytenr;
+       u32 size;
+       u64 parent;
+       u64 owner;
+       u64 flags;
+       u64 ptr;
+       u64 gen = 0;
+       int ret = 0;
+       int i;
+       int nritems;
+       struct btrfs_key key;
+       struct cache_extent *cache;
+       int reada_bits;
+
+       nritems = pick_next_pending(pending, reada, nodes, *last, bits,
+                                   bits_nr, &reada_bits);
+       if (nritems == 0)
+               return 1;
+
+       if (!reada_bits) {
+               for(i = 0; i < nritems; i++) {
+                       ret = add_cache_extent(reada, bits[i].start,
+                                              bits[i].size);
+                       if (ret == -EEXIST)
+                               continue;
+
+                       /* fixme, get the parent transid */
+                       readahead_tree_block(root, bits[i].start,
+                                            bits[i].size, 0);
+               }
+       }
+       *last = bits[0].start;
+       bytenr = bits[0].start;
+       size = bits[0].size;
+
+       cache = lookup_cache_extent(pending, bytenr, size);
+       if (cache) {
+               remove_cache_extent(pending, cache);
+               free(cache);
+       }
+       cache = lookup_cache_extent(reada, bytenr, size);
+       if (cache) {
+               remove_cache_extent(reada, cache);
+               free(cache);
+       }
+       cache = lookup_cache_extent(nodes, bytenr, size);
+       if (cache) {
+               remove_cache_extent(nodes, cache);
+               free(cache);
+       }
+       cache = lookup_cache_extent(extent_cache, bytenr, size);
+       if (cache) {
+               rec = container_of(cache, struct extent_record, cache);
+               gen = rec->parent_generation;
+       }
+
+       /* fixme, get the real parent transid */
+       buf = read_tree_block(root, bytenr, size, gen);
+       if (!extent_buffer_uptodate(buf)) {
+               record_bad_block_io(root->fs_info,
+                                   extent_cache, bytenr, size);
+               goto out;
+       }
+
+       nritems = btrfs_header_nritems(buf);
+
+       flags = 0;
+       if (!init_extent_tree) {
+               ret = btrfs_lookup_extent_info(NULL, root, bytenr,
+                                      btrfs_header_level(buf), 1, NULL,
+                                      &flags);
+               if (ret < 0) {
+                       ret = calc_extent_flag(root, extent_cache, buf, ri, &flags);
+                       if (ret < 0) {
+                               fprintf(stderr, "Couldn't calc extent flags\n");
+                               flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
+                       }
+               }
+       } else {
+               flags = 0;
+               ret = calc_extent_flag(root, extent_cache, buf, ri, &flags);
+               if (ret < 0) {
+                       fprintf(stderr, "Couldn't calc extent flags\n");
+                       flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
+               }
+       }
+
+       if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
+               if (ri != NULL &&
                    ri->objectid != BTRFS_TREE_RELOC_OBJECTID &&
                    ri->objectid == btrfs_header_owner(buf)) {
                        /*
-                        * Ok we got to this block from it's original owner and
-                        * we have FULL_BACKREF set.  Relocation can leave
-                        * converted blocks over so this is altogether possible,
-                        * however it's not possible if the generation > the
-                        * last snapshot, so check for this case.
+                        * Ok we got to this block from it's original owner and
+                        * we have FULL_BACKREF set.  Relocation can leave
+                        * converted blocks over so this is altogether possible,
+                        * however it's not possible if the generation > the
+                        * last snapshot, so check for this case.
+                        */
+                       if (!btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC) &&
+                           btrfs_header_generation(buf) > ri->last_snapshot) {
+                               flags &= ~BTRFS_BLOCK_FLAG_FULL_BACKREF;
+                               rec->bad_full_backref = 1;
+                       }
+               }
+       } else {
+               if (ri != NULL &&
+                   (ri->objectid == BTRFS_TREE_RELOC_OBJECTID ||
+                    btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))) {
+                       flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
+                       rec->bad_full_backref = 1;
+               }
+       }
+
+       if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
+               rec->flag_block_full_backref = 1;
+               parent = bytenr;
+               owner = 0;
+       } else {
+               rec->flag_block_full_backref = 0;
+               parent = 0;
+               owner = btrfs_header_owner(buf);
+       }
+
+       ret = check_block(root, extent_cache, buf, flags);
+       if (ret)
+               goto out;
+
+       if (btrfs_is_leaf(buf)) {
+               btree_space_waste += btrfs_leaf_free_space(root, buf);
+               for (i = 0; i < nritems; i++) {
+                       struct btrfs_file_extent_item *fi;
+                       btrfs_item_key_to_cpu(buf, &key, i);
+                       /*
+                        * Check key type against the leaf owner.
+                        * Could filter quite a lot of early error if
+                        * owner is correct
+                        */
+                       if (check_type_with_root(btrfs_header_owner(buf),
+                                                key.type)) {
+                               fprintf(stderr, "ignoring invalid key\n");
+                               continue;
+                       }
+                       if (key.type == BTRFS_EXTENT_ITEM_KEY) {
+                               process_extent_item(root, extent_cache, buf,
+                                                   i);
+                               continue;
+                       }
+                       if (key.type == BTRFS_METADATA_ITEM_KEY) {
+                               process_extent_item(root, extent_cache, buf,
+                                                   i);
+                               continue;
+                       }
+                       if (key.type == BTRFS_EXTENT_CSUM_KEY) {
+                               total_csum_bytes +=
+                                       btrfs_item_size_nr(buf, i);
+                               continue;
+                       }
+                       if (key.type == BTRFS_CHUNK_ITEM_KEY) {
+                               process_chunk_item(chunk_cache, &key, buf, i);
+                               continue;
+                       }
+                       if (key.type == BTRFS_DEV_ITEM_KEY) {
+                               process_device_item(dev_cache, &key, buf, i);
+                               continue;
+                       }
+                       if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
+                               process_block_group_item(block_group_cache,
+                                       &key, buf, i);
+                               continue;
+                       }
+                       if (key.type == BTRFS_DEV_EXTENT_KEY) {
+                               process_device_extent_item(dev_extent_cache,
+                                       &key, buf, i);
+                               continue;
+
+                       }
+                       if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
+#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
+                               process_extent_ref_v0(extent_cache, buf, i);
+#else
+                               BUG();
+#endif
+                               continue;
+                       }
+
+                       if (key.type == BTRFS_TREE_BLOCK_REF_KEY) {
+                               ret = add_tree_backref(extent_cache,
+                                               key.objectid, 0, key.offset, 0);
+                               if (ret < 0)
+                                       error("add_tree_backref failed: %s",
+                                             strerror(-ret));
+                               continue;
+                       }
+                       if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
+                               ret = add_tree_backref(extent_cache,
+                                               key.objectid, key.offset, 0, 0);
+                               if (ret < 0)
+                                       error("add_tree_backref failed: %s",
+                                             strerror(-ret));
+                               continue;
+                       }
+                       if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
+                               struct btrfs_extent_data_ref *ref;
+                               ref = btrfs_item_ptr(buf, i,
+                                               struct btrfs_extent_data_ref);
+                               add_data_backref(extent_cache,
+                                       key.objectid, 0,
+                                       btrfs_extent_data_ref_root(buf, ref),
+                                       btrfs_extent_data_ref_objectid(buf,
+                                                                      ref),
+                                       btrfs_extent_data_ref_offset(buf, ref),
+                                       btrfs_extent_data_ref_count(buf, ref),
+                                       0, root->sectorsize);
+                               continue;
+                       }
+                       if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
+                               struct btrfs_shared_data_ref *ref;
+                               ref = btrfs_item_ptr(buf, i,
+                                               struct btrfs_shared_data_ref);
+                               add_data_backref(extent_cache,
+                                       key.objectid, key.offset, 0, 0, 0,
+                                       btrfs_shared_data_ref_count(buf, ref),
+                                       0, root->sectorsize);
+                               continue;
+                       }
+                       if (key.type == BTRFS_ORPHAN_ITEM_KEY) {
+                               struct bad_item *bad;
+
+                               if (key.objectid == BTRFS_ORPHAN_OBJECTID)
+                                       continue;
+                               if (!owner)
+                                       continue;
+                               bad = malloc(sizeof(struct bad_item));
+                               if (!bad)
+                                       continue;
+                               INIT_LIST_HEAD(&bad->list);
+                               memcpy(&bad->key, &key,
+                                      sizeof(struct btrfs_key));
+                               bad->root_id = owner;
+                               list_add_tail(&bad->list, &delete_items);
+                               continue;
+                       }
+                       if (key.type != BTRFS_EXTENT_DATA_KEY)
+                               continue;
+                       fi = btrfs_item_ptr(buf, i,
+                                           struct btrfs_file_extent_item);
+                       if (btrfs_file_extent_type(buf, fi) ==
+                           BTRFS_FILE_EXTENT_INLINE)
+                               continue;
+                       if (btrfs_file_extent_disk_bytenr(buf, fi) == 0)
+                               continue;
+
+                       data_bytes_allocated +=
+                               btrfs_file_extent_disk_num_bytes(buf, fi);
+                       if (data_bytes_allocated < root->sectorsize) {
+                               abort();
+                       }
+                       data_bytes_referenced +=
+                               btrfs_file_extent_num_bytes(buf, fi);
+                       add_data_backref(extent_cache,
+                               btrfs_file_extent_disk_bytenr(buf, fi),
+                               parent, owner, key.objectid, key.offset -
+                               btrfs_file_extent_offset(buf, fi), 1, 1,
+                               btrfs_file_extent_disk_num_bytes(buf, fi));
+               }
+       } else {
+               int level;
+               struct btrfs_key first_key;
+
+               first_key.objectid = 0;
+
+               if (nritems > 0)
+                       btrfs_item_key_to_cpu(buf, &first_key, 0);
+               level = btrfs_header_level(buf);
+               for (i = 0; i < nritems; i++) {
+                       struct extent_record tmpl;
+
+                       ptr = btrfs_node_blockptr(buf, i);
+                       size = root->nodesize;
+                       btrfs_node_key_to_cpu(buf, &key, i);
+                       if (ri != NULL) {
+                               if ((level == ri->drop_level)
+                                   && is_dropped_key(&key, &ri->drop_key)) {
+                                       continue;
+                               }
+                       }
+
+                       memset(&tmpl, 0, sizeof(tmpl));
+                       btrfs_cpu_key_to_disk(&tmpl.parent_key, &key);
+                       tmpl.parent_generation = btrfs_node_ptr_generation(buf, i);
+                       tmpl.start = ptr;
+                       tmpl.nr = size;
+                       tmpl.refs = 1;
+                       tmpl.metadata = 1;
+                       tmpl.max_size = size;
+                       ret = add_extent_rec(extent_cache, &tmpl);
+                       if (ret < 0)
+                               goto out;
+
+                       ret = add_tree_backref(extent_cache, ptr, parent,
+                                       owner, 1);
+                       if (ret < 0) {
+                               error("add_tree_backref failed: %s",
+                                     strerror(-ret));
+                               continue;
+                       }
+
+                       if (level > 1) {
+                               add_pending(nodes, seen, ptr, size);
+                       } else {
+                               add_pending(pending, seen, ptr, size);
+                       }
+               }
+               btree_space_waste += (BTRFS_NODEPTRS_PER_BLOCK(root) -
+                                     nritems) * sizeof(struct btrfs_key_ptr);
+       }
+       total_btree_bytes += buf->len;
+       if (fs_root_objectid(btrfs_header_owner(buf)))
+               total_fs_tree_bytes += buf->len;
+       if (btrfs_header_owner(buf) == BTRFS_EXTENT_TREE_OBJECTID)
+               total_extent_tree_bytes += buf->len;
+       if (!found_old_backref &&
+           btrfs_header_owner(buf) == BTRFS_TREE_RELOC_OBJECTID &&
+           btrfs_header_backref_rev(buf) == BTRFS_MIXED_BACKREF_REV &&
+           !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))
+               found_old_backref = 1;
+out:
+       free_extent_buffer(buf);
+       return ret;
+}
+
+static int add_root_to_pending(struct extent_buffer *buf,
+                              struct cache_tree *extent_cache,
+                              struct cache_tree *pending,
+                              struct cache_tree *seen,
+                              struct cache_tree *nodes,
+                              u64 objectid)
+{
+       struct extent_record tmpl;
+       int ret;
+
+       if (btrfs_header_level(buf) > 0)
+               add_pending(nodes, seen, buf->start, buf->len);
+       else
+               add_pending(pending, seen, buf->start, buf->len);
+
+       memset(&tmpl, 0, sizeof(tmpl));
+       tmpl.start = buf->start;
+       tmpl.nr = buf->len;
+       tmpl.is_root = 1;
+       tmpl.refs = 1;
+       tmpl.metadata = 1;
+       tmpl.max_size = buf->len;
+       add_extent_rec(extent_cache, &tmpl);
+
+       if (objectid == BTRFS_TREE_RELOC_OBJECTID ||
+           btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
+               ret = add_tree_backref(extent_cache, buf->start, buf->start,
+                               0, 1);
+       else
+               ret = add_tree_backref(extent_cache, buf->start, 0, objectid,
+                               1);
+       return ret;
+}
+
+/* as we fix the tree, we might be deleting blocks that
+ * we're tracking for repair.  This hook makes sure we
+ * remove any backrefs for blocks as we are fixing them.
+ */
+static int free_extent_hook(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root,
+                           u64 bytenr, u64 num_bytes, u64 parent,
+                           u64 root_objectid, u64 owner, u64 offset,
+                           int refs_to_drop)
+{
+       struct extent_record *rec;
+       struct cache_extent *cache;
+       int is_data;
+       struct cache_tree *extent_cache = root->fs_info->fsck_extent_cache;
+
+       is_data = owner >= BTRFS_FIRST_FREE_OBJECTID;
+       cache = lookup_cache_extent(extent_cache, bytenr, num_bytes);
+       if (!cache)
+               return 0;
+
+       rec = container_of(cache, struct extent_record, cache);
+       if (is_data) {
+               struct data_backref *back;
+               back = find_data_backref(rec, parent, root_objectid, owner,
+                                        offset, 1, bytenr, num_bytes);
+               if (!back)
+                       goto out;
+               if (back->node.found_ref) {
+                       back->found_ref -= refs_to_drop;
+                       if (rec->refs)
+                               rec->refs -= refs_to_drop;
+               }
+               if (back->node.found_extent_tree) {
+                       back->num_refs -= refs_to_drop;
+                       if (rec->extent_item_refs)
+                               rec->extent_item_refs -= refs_to_drop;
+               }
+               if (back->found_ref == 0)
+                       back->node.found_ref = 0;
+               if (back->num_refs == 0)
+                       back->node.found_extent_tree = 0;
+
+               if (!back->node.found_extent_tree && back->node.found_ref) {
+                       list_del(&back->node.list);
+                       free(back);
+               }
+       } else {
+               struct tree_backref *back;
+               back = find_tree_backref(rec, parent, root_objectid);
+               if (!back)
+                       goto out;
+               if (back->node.found_ref) {
+                       if (rec->refs)
+                               rec->refs--;
+                       back->node.found_ref = 0;
+               }
+               if (back->node.found_extent_tree) {
+                       if (rec->extent_item_refs)
+                               rec->extent_item_refs--;
+                       back->node.found_extent_tree = 0;
+               }
+               if (!back->node.found_extent_tree && back->node.found_ref) {
+                       list_del(&back->node.list);
+                       free(back);
+               }
+       }
+       maybe_free_extent_rec(extent_cache, rec);
+out:
+       return 0;
+}
+
+static int delete_extent_records(struct btrfs_trans_handle *trans,
+                                struct btrfs_root *root,
+                                struct btrfs_path *path,
+                                u64 bytenr, u64 new_len)
+{
+       struct btrfs_key key;
+       struct btrfs_key found_key;
+       struct extent_buffer *leaf;
+       int ret;
+       int slot;
+
+
+       key.objectid = bytenr;
+       key.type = (u8)-1;
+       key.offset = (u64)-1;
+
+       while(1) {
+               ret = btrfs_search_slot(trans, root->fs_info->extent_root,
+                                       &key, path, 0, 1);
+               if (ret < 0)
+                       break;
+
+               if (ret > 0) {
+                       ret = 0;
+                       if (path->slots[0] == 0)
+                               break;
+                       path->slots[0]--;
+               }
+               ret = 0;
+
+               leaf = path->nodes[0];
+               slot = path->slots[0];
+
+               btrfs_item_key_to_cpu(leaf, &found_key, slot);
+               if (found_key.objectid != bytenr)
+                       break;
+
+               if (found_key.type != BTRFS_EXTENT_ITEM_KEY &&
+                   found_key.type != BTRFS_METADATA_ITEM_KEY &&
+                   found_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
+                   found_key.type != BTRFS_EXTENT_DATA_REF_KEY &&
+                   found_key.type != BTRFS_EXTENT_REF_V0_KEY &&
+                   found_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
+                   found_key.type != BTRFS_SHARED_DATA_REF_KEY) {
+                       btrfs_release_path(path);
+                       if (found_key.type == 0) {
+                               if (found_key.offset == 0)
+                                       break;
+                               key.offset = found_key.offset - 1;
+                               key.type = found_key.type;
+                       }
+                       key.type = found_key.type - 1;
+                       key.offset = (u64)-1;
+                       continue;
+               }
+
+               fprintf(stderr, "repair deleting extent record: key %Lu %u %Lu\n",
+                       found_key.objectid, found_key.type, found_key.offset);
+
+               ret = btrfs_del_item(trans, root->fs_info->extent_root, path);
+               if (ret)
+                       break;
+               btrfs_release_path(path);
+
+               if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
+                   found_key.type == BTRFS_METADATA_ITEM_KEY) {
+                       u64 bytes = (found_key.type == BTRFS_EXTENT_ITEM_KEY) ?
+                               found_key.offset : root->nodesize;
+
+                       ret = btrfs_update_block_group(trans, root, bytenr,
+                                                      bytes, 0, 0);
+                       if (ret)
+                               break;
+               }
+       }
+
+       btrfs_release_path(path);
+       return ret;
+}
+
+/*
+ * for a single backref, this will allocate a new extent
+ * and add the backref to it.
+ */
+static int record_extent(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *info,
+                        struct btrfs_path *path,
+                        struct extent_record *rec,
+                        struct extent_backref *back,
+                        int allocated, u64 flags)
+{
+       int ret;
+       struct btrfs_root *extent_root = info->extent_root;
+       struct extent_buffer *leaf;
+       struct btrfs_key ins_key;
+       struct btrfs_extent_item *ei;
+       struct data_backref *dback;
+       struct btrfs_tree_block_info *bi;
+
+       if (!back->is_data)
+               rec->max_size = max_t(u64, rec->max_size,
+                                   info->extent_root->nodesize);
+
+       if (!allocated) {
+               u32 item_size = sizeof(*ei);
+
+               if (!back->is_data)
+                       item_size += sizeof(*bi);
+
+               ins_key.objectid = rec->start;
+               ins_key.offset = rec->max_size;
+               ins_key.type = BTRFS_EXTENT_ITEM_KEY;
+
+               ret = btrfs_insert_empty_item(trans, extent_root, path,
+                                       &ins_key, item_size);
+               if (ret)
+                       goto fail;
+
+               leaf = path->nodes[0];
+               ei = btrfs_item_ptr(leaf, path->slots[0],
+                                   struct btrfs_extent_item);
+
+               btrfs_set_extent_refs(leaf, ei, 0);
+               btrfs_set_extent_generation(leaf, ei, rec->generation);
+
+               if (back->is_data) {
+                       btrfs_set_extent_flags(leaf, ei,
+                                              BTRFS_EXTENT_FLAG_DATA);
+               } else {
+                       struct btrfs_disk_key copy_key;;
+
+                       bi = (struct btrfs_tree_block_info *)(ei + 1);
+                       memset_extent_buffer(leaf, 0, (unsigned long)bi,
+                                            sizeof(*bi));
+
+                       btrfs_set_disk_key_objectid(&copy_key,
+                                                   rec->info_objectid);
+                       btrfs_set_disk_key_type(&copy_key, 0);
+                       btrfs_set_disk_key_offset(&copy_key, 0);
+
+                       btrfs_set_tree_block_level(leaf, bi, rec->info_level);
+                       btrfs_set_tree_block_key(leaf, bi, &copy_key);
+
+                       btrfs_set_extent_flags(leaf, ei,
+                                              BTRFS_EXTENT_FLAG_TREE_BLOCK | flags);
+               }
+
+               btrfs_mark_buffer_dirty(leaf);
+               ret = btrfs_update_block_group(trans, extent_root, rec->start,
+                                              rec->max_size, 1, 0);
+               if (ret)
+                       goto fail;
+               btrfs_release_path(path);
+       }
+
+       if (back->is_data) {
+               u64 parent;
+               int i;
+
+               dback = to_data_backref(back);
+               if (back->full_backref)
+                       parent = dback->parent;
+               else
+                       parent = 0;
+
+               for (i = 0; i < dback->found_ref; i++) {
+                       /* if parent != 0, we're doing a full backref
+                        * passing BTRFS_FIRST_FREE_OBJECTID as the owner
+                        * just makes the backref allocator create a data
+                        * backref
+                        */
+                       ret = btrfs_inc_extent_ref(trans, info->extent_root,
+                                                  rec->start, rec->max_size,
+                                                  parent,
+                                                  dback->root,
+                                                  parent ?
+                                                  BTRFS_FIRST_FREE_OBJECTID :
+                                                  dback->owner,
+                                                  dback->offset);
+                       if (ret)
+                               break;
+               }
+               fprintf(stderr, "adding new data backref"
+                               " on %llu %s %llu owner %llu"
+                               " offset %llu found %d\n",
+                               (unsigned long long)rec->start,
+                               back->full_backref ?
+                               "parent" : "root",
+                               back->full_backref ?
+                               (unsigned long long)parent :
+                               (unsigned long long)dback->root,
+                               (unsigned long long)dback->owner,
+                               (unsigned long long)dback->offset,
+                               dback->found_ref);
+       } else {
+               u64 parent;
+               struct tree_backref *tback;
+
+               tback = to_tree_backref(back);
+               if (back->full_backref)
+                       parent = tback->parent;
+               else
+                       parent = 0;
+
+               ret = btrfs_inc_extent_ref(trans, info->extent_root,
+                                          rec->start, rec->max_size,
+                                          parent, tback->root, 0, 0);
+               fprintf(stderr, "adding new tree backref on "
+                       "start %llu len %llu parent %llu root %llu\n",
+                       rec->start, rec->max_size, parent, tback->root);
+       }
+fail:
+       btrfs_release_path(path);
+       return ret;
+}
+
+static struct extent_entry *find_entry(struct list_head *entries,
+                                      u64 bytenr, u64 bytes)
+{
+       struct extent_entry *entry = NULL;
+
+       list_for_each_entry(entry, entries, list) {
+               if (entry->bytenr == bytenr && entry->bytes == bytes)
+                       return entry;
+       }
+
+       return NULL;
+}
+
+static struct extent_entry *find_most_right_entry(struct list_head *entries)
+{
+       struct extent_entry *entry, *best = NULL, *prev = NULL;
+
+       list_for_each_entry(entry, entries, list) {
+               /*
+                * If there are as many broken entries as entries then we know
+                * not to trust this particular entry.
+                */
+               if (entry->broken == entry->count)
+                       continue;
+
+               /*
+                * Special case, when there are only two entries and 'best' is
+                * the first one
+                */
+               if (!prev) {
+                       best = entry;
+                       prev = entry;
+                       continue;
+               }
+
+               /*
+                * If our current entry == best then we can't be sure our best
+                * is really the best, so we need to keep searching.
+                */
+               if (best && best->count == entry->count) {
+                       prev = entry;
+                       best = NULL;
+                       continue;
+               }
+
+               /* Prev == entry, not good enough, have to keep searching */
+               if (!prev->broken && prev->count == entry->count)
+                       continue;
+
+               if (!best)
+                       best = (prev->count > entry->count) ? prev : entry;
+               else if (best->count < entry->count)
+                       best = entry;
+               prev = entry;
+       }
+
+       return best;
+}
+
+static int repair_ref(struct btrfs_fs_info *info, struct btrfs_path *path,
+                     struct data_backref *dback, struct extent_entry *entry)
+{
+       struct btrfs_trans_handle *trans;
+       struct btrfs_root *root;
+       struct btrfs_file_extent_item *fi;
+       struct extent_buffer *leaf;
+       struct btrfs_key key;
+       u64 bytenr, bytes;
+       int ret, err;
+
+       key.objectid = dback->root;
+       key.type = BTRFS_ROOT_ITEM_KEY;
+       key.offset = (u64)-1;
+       root = btrfs_read_fs_root(info, &key);
+       if (IS_ERR(root)) {
+               fprintf(stderr, "Couldn't find root for our ref\n");
+               return -EINVAL;
+       }
+
+       /*
+        * The backref points to the original offset of the extent if it was
+        * split, so we need to search down to the offset we have and then walk
+        * forward until we find the backref we're looking for.
+        */
+       key.objectid = dback->owner;
+       key.type = BTRFS_EXTENT_DATA_KEY;
+       key.offset = dback->offset;
+       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       if (ret < 0) {
+               fprintf(stderr, "Error looking up ref %d\n", ret);
+               return ret;
+       }
+
+       while (1) {
+               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+                       ret = btrfs_next_leaf(root, path);
+                       if (ret) {
+                               fprintf(stderr, "Couldn't find our ref, next\n");
+                               return -EINVAL;
+                       }
+               }
+               leaf = path->nodes[0];
+               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+               if (key.objectid != dback->owner ||
+                   key.type != BTRFS_EXTENT_DATA_KEY) {
+                       fprintf(stderr, "Couldn't find our ref, search\n");
+                       return -EINVAL;
+               }
+               fi = btrfs_item_ptr(leaf, path->slots[0],
+                                   struct btrfs_file_extent_item);
+               bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+               bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
+
+               if (bytenr == dback->disk_bytenr && bytes == dback->bytes)
+                       break;
+               path->slots[0]++;
+       }
+
+       btrfs_release_path(path);
+
+       trans = btrfs_start_transaction(root, 1);
+       if (IS_ERR(trans))
+               return PTR_ERR(trans);
+
+       /*
+        * Ok we have the key of the file extent we want to fix, now we can cow
+        * down to the thing and fix it.
+        */
+       ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+       if (ret < 0) {
+               fprintf(stderr, "Error cowing down to ref [%Lu, %u, %Lu]: %d\n",
+                       key.objectid, key.type, key.offset, ret);
+               goto out;
+       }
+       if (ret > 0) {
+               fprintf(stderr, "Well that's odd, we just found this key "
+                       "[%Lu, %u, %Lu]\n", key.objectid, key.type,
+                       key.offset);
+               ret = -EINVAL;
+               goto out;
+       }
+       leaf = path->nodes[0];
+       fi = btrfs_item_ptr(leaf, path->slots[0],
+                           struct btrfs_file_extent_item);
+
+       if (btrfs_file_extent_compression(leaf, fi) &&
+           dback->disk_bytenr != entry->bytenr) {
+               fprintf(stderr, "Ref doesn't match the record start and is "
+                       "compressed, please take a btrfs-image of this file "
+                       "system and send it to a btrfs developer so they can "
+                       "complete this functionality for bytenr %Lu\n",
+                       dback->disk_bytenr);
+               ret = -EINVAL;
+               goto out;
+       }
+
+       if (dback->node.broken && dback->disk_bytenr != entry->bytenr) {
+               btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
+       } else if (dback->disk_bytenr > entry->bytenr) {
+               u64 off_diff, offset;
+
+               off_diff = dback->disk_bytenr - entry->bytenr;
+               offset = btrfs_file_extent_offset(leaf, fi);
+               if (dback->disk_bytenr + offset +
+                   btrfs_file_extent_num_bytes(leaf, fi) >
+                   entry->bytenr + entry->bytes) {
+                       fprintf(stderr, "Ref is past the entry end, please "
+                               "take a btrfs-image of this file system and "
+                               "send it to a btrfs developer, ref %Lu\n",
+                               dback->disk_bytenr);
+                       ret = -EINVAL;
+                       goto out;
+               }
+               offset += off_diff;
+               btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
+               btrfs_set_file_extent_offset(leaf, fi, offset);
+       } else if (dback->disk_bytenr < entry->bytenr) {
+               u64 offset;
+
+               offset = btrfs_file_extent_offset(leaf, fi);
+               if (dback->disk_bytenr + offset < entry->bytenr) {
+                       fprintf(stderr, "Ref is before the entry start, please"
+                               " take a btrfs-image of this file system and "
+                               "send it to a btrfs developer, ref %Lu\n",
+                               dback->disk_bytenr);
+                       ret = -EINVAL;
+                       goto out;
+               }
+
+               offset += dback->disk_bytenr;
+               offset -= entry->bytenr;
+               btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
+               btrfs_set_file_extent_offset(leaf, fi, offset);
+       }
+
+       btrfs_set_file_extent_disk_num_bytes(leaf, fi, entry->bytes);
+
+       /*
+        * Chances are if disk_num_bytes were wrong then so is ram_bytes, but
+        * only do this if we aren't using compression, otherwise it's a
+        * trickier case.
+        */
+       if (!btrfs_file_extent_compression(leaf, fi))
+               btrfs_set_file_extent_ram_bytes(leaf, fi, entry->bytes);
+       else
+               printf("ram bytes may be wrong?\n");
+       btrfs_mark_buffer_dirty(leaf);
+out:
+       err = btrfs_commit_transaction(trans, root);
+       btrfs_release_path(path);
+       return ret ? ret : err;
+}
+
+static int verify_backrefs(struct btrfs_fs_info *info, struct btrfs_path *path,
+                          struct extent_record *rec)
+{
+       struct extent_backref *back;
+       struct data_backref *dback;
+       struct extent_entry *entry, *best = NULL;
+       LIST_HEAD(entries);
+       int nr_entries = 0;
+       int broken_entries = 0;
+       int ret = 0;
+       short mismatch = 0;
+
+       /*
+        * Metadata is easy and the backrefs should always agree on bytenr and
+        * size, if not we've got bigger issues.
+        */
+       if (rec->metadata)
+               return 0;
+
+       list_for_each_entry(back, &rec->backrefs, list) {
+               if (back->full_backref || !back->is_data)
+                       continue;
+
+               dback = to_data_backref(back);
+
+               /*
+                * We only pay attention to backrefs that we found a real
+                * backref for.
+                */
+               if (dback->found_ref == 0)
+                       continue;
+
+               /*
+                * For now we only catch when the bytes don't match, not the
+                * bytenr.  We can easily do this at the same time, but I want
+                * to have a fs image to test on before we just add repair
+                * functionality willy-nilly so we know we won't screw up the
+                * repair.
+                */
+
+               entry = find_entry(&entries, dback->disk_bytenr,
+                                  dback->bytes);
+               if (!entry) {
+                       entry = malloc(sizeof(struct extent_entry));
+                       if (!entry) {
+                               ret = -ENOMEM;
+                               goto out;
+                       }
+                       memset(entry, 0, sizeof(*entry));
+                       entry->bytenr = dback->disk_bytenr;
+                       entry->bytes = dback->bytes;
+                       list_add_tail(&entry->list, &entries);
+                       nr_entries++;
+               }
+
+               /*
+                * If we only have on entry we may think the entries agree when
+                * in reality they don't so we have to do some extra checking.
+                */
+               if (dback->disk_bytenr != rec->start ||
+                   dback->bytes != rec->nr || back->broken)
+                       mismatch = 1;
+
+               if (back->broken) {
+                       entry->broken++;
+                       broken_entries++;
+               }
+
+               entry->count++;
+       }
+
+       /* Yay all the backrefs agree, carry on good sir */
+       if (nr_entries <= 1 && !mismatch)
+               goto out;
+
+       fprintf(stderr, "attempting to repair backref discrepency for bytenr "
+               "%Lu\n", rec->start);
+
+       /*
+        * First we want to see if the backrefs can agree amongst themselves who
+        * is right, so figure out which one of the entries has the highest
+        * count.
+        */
+       best = find_most_right_entry(&entries);
+
+       /*
+        * Ok so we may have an even split between what the backrefs think, so
+        * this is where we use the extent ref to see what it thinks.
+        */
+       if (!best) {
+               entry = find_entry(&entries, rec->start, rec->nr);
+               if (!entry && (!broken_entries || !rec->found_rec)) {
+                       fprintf(stderr, "Backrefs don't agree with each other "
+                               "and extent record doesn't agree with anybody,"
+                               " so we can't fix bytenr %Lu bytes %Lu\n",
+                               rec->start, rec->nr);
+                       ret = -EINVAL;
+                       goto out;
+               } else if (!entry) {
+                       /*
+                        * Ok our backrefs were broken, we'll assume this is the
+                        * correct value and add an entry for this range.
                         */
-                       if (!btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC) &&
-                           btrfs_header_generation(buf) > ri->last_snapshot) {
-                               flags &= ~BTRFS_BLOCK_FLAG_FULL_BACKREF;
-                               rec->bad_full_backref = 1;
+                       entry = malloc(sizeof(struct extent_entry));
+                       if (!entry) {
+                               ret = -ENOMEM;
+                               goto out;
                        }
+                       memset(entry, 0, sizeof(*entry));
+                       entry->bytenr = rec->start;
+                       entry->bytes = rec->nr;
+                       list_add_tail(&entry->list, &entries);
+                       nr_entries++;
                }
-       } else {
-               if (ri != NULL &&
-                   (ri->objectid == BTRFS_TREE_RELOC_OBJECTID ||
-                    btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))) {
-                       flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
-                       rec->bad_full_backref = 1;
+               entry->count++;
+               best = find_most_right_entry(&entries);
+               if (!best) {
+                       fprintf(stderr, "Backrefs and extent record evenly "
+                               "split on who is right, this is going to "
+                               "require user input to fix bytenr %Lu bytes "
+                               "%Lu\n", rec->start, rec->nr);
+                       ret = -EINVAL;
+                       goto out;
                }
        }
 
-       if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
-               rec->flag_block_full_backref = 1;
-               parent = bytenr;
-               owner = 0;
-       } else {
-               rec->flag_block_full_backref = 0;
-               parent = 0;
-               owner = btrfs_header_owner(buf);
+       /*
+        * I don't think this can happen currently as we'll abort() if we catch
+        * this case higher up, but in case somebody removes that we still can't
+        * deal with it properly here yet, so just bail out of that's the case.
+        */
+       if (best->bytenr != rec->start) {
+               fprintf(stderr, "Extent start and backref starts don't match, "
+                       "please use btrfs-image on this file system and send "
+                       "it to a btrfs developer so they can make fsck fix "
+                       "this particular case.  bytenr is %Lu, bytes is %Lu\n",
+                       rec->start, rec->nr);
+               ret = -EINVAL;
+               goto out;
+       }
+
+       /*
+        * Ok great we all agreed on an extent record, let's go find the real
+        * references and fix up the ones that don't match.
+        */
+       list_for_each_entry(back, &rec->backrefs, list) {
+               if (back->full_backref || !back->is_data)
+                       continue;
+
+               dback = to_data_backref(back);
+
+               /*
+                * Still ignoring backrefs that don't have a real ref attached
+                * to them.
+                */
+               if (dback->found_ref == 0)
+                       continue;
+
+               if (dback->bytes == best->bytes &&
+                   dback->disk_bytenr == best->bytenr)
+                       continue;
+
+               ret = repair_ref(info, path, dback, best);
+               if (ret)
+                       goto out;
+       }
+
+       /*
+        * Ok we messed with the actual refs, which means we need to drop our
+        * entire cache and go back and rescan.  I know this is a huge pain and
+        * adds a lot of extra work, but it's the only way to be safe.  Once all
+        * the backrefs agree we may not need to do anything to the extent
+        * record itself.
+        */
+       ret = -EAGAIN;
+out:
+       while (!list_empty(&entries)) {
+               entry = list_entry(entries.next, struct extent_entry, list);
+               list_del_init(&entry->list);
+               free(entry);
        }
+       return ret;
+}
 
-       ret = check_block(root, extent_cache, buf, flags);
-       if (ret)
-               goto out;
+static int process_duplicates(struct btrfs_root *root,
+                             struct cache_tree *extent_cache,
+                             struct extent_record *rec)
+{
+       struct extent_record *good, *tmp;
+       struct cache_extent *cache;
+       int ret;
 
-       if (btrfs_is_leaf(buf)) {
-               btree_space_waste += btrfs_leaf_free_space(root, buf);
-               for (i = 0; i < nritems; i++) {
-                       struct btrfs_file_extent_item *fi;
-                       btrfs_item_key_to_cpu(buf, &key, i);
-                       if (key.type == BTRFS_EXTENT_ITEM_KEY) {
-                               process_extent_item(root, extent_cache, buf,
-                                                   i);
-                               continue;
-                       }
-                       if (key.type == BTRFS_METADATA_ITEM_KEY) {
-                               process_extent_item(root, extent_cache, buf,
-                                                   i);
-                               continue;
-                       }
-                       if (key.type == BTRFS_EXTENT_CSUM_KEY) {
-                               total_csum_bytes +=
-                                       btrfs_item_size_nr(buf, i);
-                               continue;
-                       }
-                       if (key.type == BTRFS_CHUNK_ITEM_KEY) {
-                               process_chunk_item(chunk_cache, &key, buf, i);
-                               continue;
-                       }
-                       if (key.type == BTRFS_DEV_ITEM_KEY) {
-                               process_device_item(dev_cache, &key, buf, i);
-                               continue;
-                       }
-                       if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
-                               process_block_group_item(block_group_cache,
-                                       &key, buf, i);
-                               continue;
-                       }
-                       if (key.type == BTRFS_DEV_EXTENT_KEY) {
-                               process_device_extent_item(dev_extent_cache,
-                                       &key, buf, i);
-                               continue;
+       /*
+        * If we found a extent record for this extent then return, or if we
+        * have more than one duplicate we are likely going to need to delete
+        * something.
+        */
+       if (rec->found_rec || rec->num_duplicates > 1)
+               return 0;
 
-                       }
-                       if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
-#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
-                               process_extent_ref_v0(extent_cache, buf, i);
-#else
-                               BUG();
-#endif
-                               continue;
-                       }
+       /* Shouldn't happen but just in case */
+       BUG_ON(!rec->num_duplicates);
 
-                       if (key.type == BTRFS_TREE_BLOCK_REF_KEY) {
-                               add_tree_backref(extent_cache, key.objectid, 0,
-                                                key.offset, 0);
-                               continue;
-                       }
-                       if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
-                               add_tree_backref(extent_cache, key.objectid,
-                                                key.offset, 0, 0);
-                               continue;
-                       }
-                       if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
-                               struct btrfs_extent_data_ref *ref;
-                               ref = btrfs_item_ptr(buf, i,
-                                               struct btrfs_extent_data_ref);
-                               add_data_backref(extent_cache,
-                                       key.objectid, 0,
-                                       btrfs_extent_data_ref_root(buf, ref),
-                                       btrfs_extent_data_ref_objectid(buf,
-                                                                      ref),
-                                       btrfs_extent_data_ref_offset(buf, ref),
-                                       btrfs_extent_data_ref_count(buf, ref),
-                                       0, root->sectorsize);
-                               continue;
-                       }
-                       if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
-                               struct btrfs_shared_data_ref *ref;
-                               ref = btrfs_item_ptr(buf, i,
-                                               struct btrfs_shared_data_ref);
-                               add_data_backref(extent_cache,
-                                       key.objectid, key.offset, 0, 0, 0,
-                                       btrfs_shared_data_ref_count(buf, ref),
-                                       0, root->sectorsize);
-                               continue;
-                       }
-                       if (key.type == BTRFS_ORPHAN_ITEM_KEY) {
-                               struct bad_item *bad;
+       /*
+        * So this happens if we end up with a backref that doesn't match the
+        * actual extent entry.  So either the backref is bad or the extent
+        * entry is bad.  Either way we want to have the extent_record actually
+        * reflect what we found in the extent_tree, so we need to take the
+        * duplicate out and use that as the extent_record since the only way we
+        * get a duplicate is if we find a real life BTRFS_EXTENT_ITEM_KEY.
+        */
+       remove_cache_extent(extent_cache, &rec->cache);
 
-                               if (key.objectid == BTRFS_ORPHAN_OBJECTID)
-                                       continue;
-                               if (!owner)
-                                       continue;
-                               bad = malloc(sizeof(struct bad_item));
-                               if (!bad)
-                                       continue;
-                               INIT_LIST_HEAD(&bad->list);
-                               memcpy(&bad->key, &key,
-                                      sizeof(struct btrfs_key));
-                               bad->root_id = owner;
-                               list_add_tail(&bad->list, &delete_items);
-                               continue;
-                       }
-                       if (key.type != BTRFS_EXTENT_DATA_KEY)
-                               continue;
-                       fi = btrfs_item_ptr(buf, i,
-                                           struct btrfs_file_extent_item);
-                       if (btrfs_file_extent_type(buf, fi) ==
-                           BTRFS_FILE_EXTENT_INLINE)
-                               continue;
-                       if (btrfs_file_extent_disk_bytenr(buf, fi) == 0)
-                               continue;
+       good = to_extent_record(rec->dups.next);
+       list_del_init(&good->list);
+       INIT_LIST_HEAD(&good->backrefs);
+       INIT_LIST_HEAD(&good->dups);
+       good->cache.start = good->start;
+       good->cache.size = good->nr;
+       good->content_checked = 0;
+       good->owner_ref_checked = 0;
+       good->num_duplicates = 0;
+       good->refs = rec->refs;
+       list_splice_init(&rec->backrefs, &good->backrefs);
+       while (1) {
+               cache = lookup_cache_extent(extent_cache, good->start,
+                                           good->nr);
+               if (!cache)
+                       break;
+               tmp = container_of(cache, struct extent_record, cache);
 
-                       data_bytes_allocated +=
-                               btrfs_file_extent_disk_num_bytes(buf, fi);
-                       if (data_bytes_allocated < root->sectorsize) {
-                               abort();
-                       }
-                       data_bytes_referenced +=
-                               btrfs_file_extent_num_bytes(buf, fi);
-                       add_data_backref(extent_cache,
-                               btrfs_file_extent_disk_bytenr(buf, fi),
-                               parent, owner, key.objectid, key.offset -
-                               btrfs_file_extent_offset(buf, fi), 1, 1,
-                               btrfs_file_extent_disk_num_bytes(buf, fi));
+               /*
+                * If we find another overlapping extent and it's found_rec is
+                * set then it's a duplicate and we need to try and delete
+                * something.
+                */
+               if (tmp->found_rec || tmp->num_duplicates > 0) {
+                       if (list_empty(&good->list))
+                               list_add_tail(&good->list,
+                                             &duplicate_extents);
+                       good->num_duplicates += tmp->num_duplicates + 1;
+                       list_splice_init(&tmp->dups, &good->dups);
+                       list_del_init(&tmp->list);
+                       list_add_tail(&tmp->list, &good->dups);
+                       remove_cache_extent(extent_cache, &tmp->cache);
+                       continue;
                }
-       } else {
-               int level;
-               struct btrfs_key first_key;
 
-               first_key.objectid = 0;
+               /*
+                * Ok we have another non extent item backed extent rec, so lets
+                * just add it to this extent and carry on like we did above.
+                */
+               good->refs += tmp->refs;
+               list_splice_init(&tmp->backrefs, &good->backrefs);
+               remove_cache_extent(extent_cache, &tmp->cache);
+               free(tmp);
+       }
+       ret = insert_cache_extent(extent_cache, &good->cache);
+       BUG_ON(ret);
+       free(rec);
+       return good->num_duplicates ? 0 : 1;
+}
 
-               if (nritems > 0)
-                       btrfs_item_key_to_cpu(buf, &first_key, 0);
-               level = btrfs_header_level(buf);
-               for (i = 0; i < nritems; i++) {
-                       ptr = btrfs_node_blockptr(buf, i);
-                       size = root->nodesize;
-                       btrfs_node_key_to_cpu(buf, &key, i);
-                       if (ri != NULL) {
-                               if ((level == ri->drop_level)
-                                   && is_dropped_key(&key, &ri->drop_key)) {
-                                       continue;
-                               }
-                       }
-                       ret = add_extent_rec(extent_cache, &key,
-                                            btrfs_node_ptr_generation(buf, i),
-                                            ptr, size, 0, 0, 1, 0, 1, 0,
-                                            size);
-                       BUG_ON(ret);
+static int delete_duplicate_records(struct btrfs_root *root,
+                                   struct extent_record *rec)
+{
+       struct btrfs_trans_handle *trans;
+       LIST_HEAD(delete_list);
+       struct btrfs_path path;
+       struct extent_record *tmp, *good, *n;
+       int nr_del = 0;
+       int ret = 0, err;
+       struct btrfs_key key;
 
-                       add_tree_backref(extent_cache, ptr, parent, owner, 1);
+       btrfs_init_path(&path);
 
-                       if (level > 1) {
-                               add_pending(nodes, seen, ptr, size);
-                       } else {
-                               add_pending(pending, seen, ptr, size);
-                       }
+       good = rec;
+       /* Find the record that covers all of the duplicates. */
+       list_for_each_entry(tmp, &rec->dups, list) {
+               if (good->start < tmp->start)
+                       continue;
+               if (good->nr > tmp->nr)
+                       continue;
+
+               if (tmp->start + tmp->nr < good->start + good->nr) {
+                       fprintf(stderr, "Ok we have overlapping extents that "
+                               "aren't completely covered by each other, this "
+                               "is going to require more careful thought.  "
+                               "The extents are [%Lu-%Lu] and [%Lu-%Lu]\n",
+                               tmp->start, tmp->nr, good->start, good->nr);
+                       abort();
                }
-               btree_space_waste += (BTRFS_NODEPTRS_PER_BLOCK(root) -
-                                     nritems) * sizeof(struct btrfs_key_ptr);
+               good = tmp;
        }
-       total_btree_bytes += buf->len;
-       if (fs_root_objectid(btrfs_header_owner(buf)))
-               total_fs_tree_bytes += buf->len;
-       if (btrfs_header_owner(buf) == BTRFS_EXTENT_TREE_OBJECTID)
-               total_extent_tree_bytes += buf->len;
-       if (!found_old_backref &&
-           btrfs_header_owner(buf) == BTRFS_TREE_RELOC_OBJECTID &&
-           btrfs_header_backref_rev(buf) == BTRFS_MIXED_BACKREF_REV &&
-           !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))
-               found_old_backref = 1;
-out:
-       free_extent_buffer(buf);
-       return ret;
-}
 
-static int add_root_to_pending(struct extent_buffer *buf,
-                              struct cache_tree *extent_cache,
-                              struct cache_tree *pending,
-                              struct cache_tree *seen,
-                              struct cache_tree *nodes,
-                              u64 objectid)
-{
-       if (btrfs_header_level(buf) > 0)
-               add_pending(nodes, seen, buf->start, buf->len);
-       else
-               add_pending(pending, seen, buf->start, buf->len);
-       add_extent_rec(extent_cache, NULL, 0, buf->start, buf->len,
-                      0, 1, 1, 0, 1, 0, buf->len);
+       if (good != rec)
+               list_add_tail(&rec->list, &delete_list);
 
-       if (objectid == BTRFS_TREE_RELOC_OBJECTID ||
-           btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
-               add_tree_backref(extent_cache, buf->start, buf->start,
-                                0, 1);
-       else
-               add_tree_backref(extent_cache, buf->start, 0, objectid, 1);
-       return 0;
-}
+       list_for_each_entry_safe(tmp, n, &rec->dups, list) {
+               if (tmp == good)
+                       continue;
+               list_move_tail(&tmp->list, &delete_list);
+       }
 
-/* as we fix the tree, we might be deleting blocks that
- * we're tracking for repair.  This hook makes sure we
- * remove any backrefs for blocks as we are fixing them.
- */
-static int free_extent_hook(struct btrfs_trans_handle *trans,
-                           struct btrfs_root *root,
-                           u64 bytenr, u64 num_bytes, u64 parent,
-                           u64 root_objectid, u64 owner, u64 offset,
-                           int refs_to_drop)
-{
-       struct extent_record *rec;
-       struct cache_extent *cache;
-       int is_data;
-       struct cache_tree *extent_cache = root->fs_info->fsck_extent_cache;
+       root = root->fs_info->extent_root;
+       trans = btrfs_start_transaction(root, 1);
+       if (IS_ERR(trans)) {
+               ret = PTR_ERR(trans);
+               goto out;
+       }
 
-       is_data = owner >= BTRFS_FIRST_FREE_OBJECTID;
-       cache = lookup_cache_extent(extent_cache, bytenr, num_bytes);
-       if (!cache)
-               return 0;
+       list_for_each_entry(tmp, &delete_list, list) {
+               if (tmp->found_rec == 0)
+                       continue;
+               key.objectid = tmp->start;
+               key.type = BTRFS_EXTENT_ITEM_KEY;
+               key.offset = tmp->nr;
 
-       rec = container_of(cache, struct extent_record, cache);
-       if (is_data) {
-               struct data_backref *back;
-               back = find_data_backref(rec, parent, root_objectid, owner,
-                                        offset, 1, bytenr, num_bytes);
-               if (!back)
-                       goto out;
-               if (back->node.found_ref) {
-                       back->found_ref -= refs_to_drop;
-                       if (rec->refs)
-                               rec->refs -= refs_to_drop;
-               }
-               if (back->node.found_extent_tree) {
-                       back->num_refs -= refs_to_drop;
-                       if (rec->extent_item_refs)
-                               rec->extent_item_refs -= refs_to_drop;
+               /* Shouldn't happen but just in case */
+               if (tmp->metadata) {
+                       fprintf(stderr, "Well this shouldn't happen, extent "
+                               "record overlaps but is metadata? "
+                               "[%Lu, %Lu]\n", tmp->start, tmp->nr);
+                       abort();
                }
-               if (back->found_ref == 0)
-                       back->node.found_ref = 0;
-               if (back->num_refs == 0)
-                       back->node.found_extent_tree = 0;
 
-               if (!back->node.found_extent_tree && back->node.found_ref) {
-                       list_del(&back->node.list);
-                       free(back);
-               }
-       } else {
-               struct tree_backref *back;
-               back = find_tree_backref(rec, parent, root_objectid);
-               if (!back)
-                       goto out;
-               if (back->node.found_ref) {
-                       if (rec->refs)
-                               rec->refs--;
-                       back->node.found_ref = 0;
-               }
-               if (back->node.found_extent_tree) {
-                       if (rec->extent_item_refs)
-                               rec->extent_item_refs--;
-                       back->node.found_extent_tree = 0;
-               }
-               if (!back->node.found_extent_tree && back->node.found_ref) {
-                       list_del(&back->node.list);
-                       free(back);
+               ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
+               if (ret) {
+                       if (ret > 0)
+                               ret = -EINVAL;
+                       break;
                }
+               ret = btrfs_del_item(trans, root, &path);
+               if (ret)
+                       break;
+               btrfs_release_path(&path);
+               nr_del++;
        }
-       maybe_free_extent_rec(extent_cache, rec);
+       err = btrfs_commit_transaction(trans, root);
+       if (err && !ret)
+               ret = err;
 out:
-       return 0;
+       while (!list_empty(&delete_list)) {
+               tmp = to_extent_record(delete_list.next);
+               list_del_init(&tmp->list);
+               if (tmp == rec)
+                       continue;
+               free(tmp);
+       }
+
+       while (!list_empty(&rec->dups)) {
+               tmp = to_extent_record(rec->dups.next);
+               list_del_init(&tmp->list);
+               free(tmp);
+       }
+
+       btrfs_release_path(&path);
+
+       if (!ret && !nr_del)
+               rec->num_duplicates = 0;
+
+       return ret ? ret : nr_del;
 }
 
-static int delete_extent_records(struct btrfs_trans_handle *trans,
-                                struct btrfs_root *root,
-                                struct btrfs_path *path,
-                                u64 bytenr, u64 new_len)
+static int find_possible_backrefs(struct btrfs_fs_info *info,
+                                 struct btrfs_path *path,
+                                 struct cache_tree *extent_cache,
+                                 struct extent_record *rec)
 {
+       struct btrfs_root *root;
+       struct extent_backref *back;
+       struct data_backref *dback;
+       struct cache_extent *cache;
+       struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
-       struct btrfs_key found_key;
-       struct extent_buffer *leaf;
+       u64 bytenr, bytes;
        int ret;
-       int slot;
 
+       list_for_each_entry(back, &rec->backrefs, list) {
+               /* Don't care about full backrefs (poor unloved backrefs) */
+               if (back->full_backref || !back->is_data)
+                       continue;
 
-       key.objectid = bytenr;
-       key.type = (u8)-1;
-       key.offset = (u64)-1;
+               dback = to_data_backref(back);
 
-       while(1) {
-               ret = btrfs_search_slot(trans, root->fs_info->extent_root,
-                                       &key, path, 0, 1);
-               if (ret < 0)
-                       break;
+               /* We found this one, we don't need to do a lookup */
+               if (dback->found_ref)
+                       continue;
 
-               if (ret > 0) {
-                       ret = 0;
-                       if (path->slots[0] == 0)
-                               break;
-                       path->slots[0]--;
-               }
-               ret = 0;
+               key.objectid = dback->root;
+               key.type = BTRFS_ROOT_ITEM_KEY;
+               key.offset = (u64)-1;
 
-               leaf = path->nodes[0];
-               slot = path->slots[0];
+               root = btrfs_read_fs_root(info, &key);
 
-               btrfs_item_key_to_cpu(leaf, &found_key, slot);
-               if (found_key.objectid != bytenr)
-                       break;
+               /* No root, definitely a bad ref, skip */
+               if (IS_ERR(root) && PTR_ERR(root) == -ENOENT)
+                       continue;
+               /* Other err, exit */
+               if (IS_ERR(root))
+                       return PTR_ERR(root);
 
-               if (found_key.type != BTRFS_EXTENT_ITEM_KEY &&
-                   found_key.type != BTRFS_METADATA_ITEM_KEY &&
-                   found_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
-                   found_key.type != BTRFS_EXTENT_DATA_REF_KEY &&
-                   found_key.type != BTRFS_EXTENT_REF_V0_KEY &&
-                   found_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
-                   found_key.type != BTRFS_SHARED_DATA_REF_KEY) {
+               key.objectid = dback->owner;
+               key.type = BTRFS_EXTENT_DATA_KEY;
+               key.offset = dback->offset;
+               ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+               if (ret) {
                        btrfs_release_path(path);
-                       if (found_key.type == 0) {
-                               if (found_key.offset == 0)
-                                       break;
-                               key.offset = found_key.offset - 1;
-                               key.type = found_key.type;
-                       }
-                       key.type = found_key.type - 1;
-                       key.offset = (u64)-1;
+                       if (ret < 0)
+                               return ret;
+                       /* Didn't find it, we can carry on */
+                       ret = 0;
                        continue;
                }
 
-               fprintf(stderr, "repair deleting extent record: key %Lu %u %Lu\n",
-                       found_key.objectid, found_key.type, found_key.offset);
-
-               ret = btrfs_del_item(trans, root->fs_info->extent_root, path);
-               if (ret)
-                       break;
+               fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                   struct btrfs_file_extent_item);
+               bytenr = btrfs_file_extent_disk_bytenr(path->nodes[0], fi);
+               bytes = btrfs_file_extent_disk_num_bytes(path->nodes[0], fi);
                btrfs_release_path(path);
+               cache = lookup_cache_extent(extent_cache, bytenr, 1);
+               if (cache) {
+                       struct extent_record *tmp;
+                       tmp = container_of(cache, struct extent_record, cache);
 
-               if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
-                   found_key.type == BTRFS_METADATA_ITEM_KEY) {
-                       u64 bytes = (found_key.type == BTRFS_EXTENT_ITEM_KEY) ?
-                               found_key.offset : root->nodesize;
-
-                       ret = btrfs_update_block_group(trans, root, bytenr,
-                                                      bytes, 0, 0);
-                       if (ret)
-                               break;
+                       /*
+                        * If we found an extent record for the bytenr for this
+                        * particular backref then we can't add it to our
+                        * current extent record.  We only want to add backrefs
+                        * that don't have a corresponding extent item in the
+                        * extent tree since they likely belong to this record
+                        * and we need to fix it if it doesn't match bytenrs.
+                        */
+                       if  (tmp->found_rec)
+                               continue;
                }
+
+               dback->found_ref += 1;
+               dback->disk_bytenr = bytenr;
+               dback->bytes = bytes;
+
+               /*
+                * Set this so the verify backref code knows not to trust the
+                * values in this backref.
+                */
+               back->broken = 1;
        }
 
-       btrfs_release_path(path);
-       return ret;
+       return 0;
 }
 
 /*
- * for a single backref, this will allocate a new extent
- * and add the backref to it.
+ * Record orphan data ref into corresponding root.
+ *
+ * Return 0 if the extent item contains data ref and recorded.
+ * Return 1 if the extent item contains no useful data ref
+ *   On that case, it may contains only shared_dataref or metadata backref
+ *   or the file extent exists(this should be handled by the extent bytenr
+ *   recovery routine)
+ * Return <0 if something goes wrong.
  */
-static int record_extent(struct btrfs_trans_handle *trans,
-                        struct btrfs_fs_info *info,
-                        struct btrfs_path *path,
-                        struct extent_record *rec,
-                        struct extent_backref *back,
-                        int allocated, u64 flags)
+static int record_orphan_data_extents(struct btrfs_fs_info *fs_info,
+                                     struct extent_record *rec)
 {
-       int ret;
-       struct btrfs_root *extent_root = info->extent_root;
-       struct extent_buffer *leaf;
-       struct btrfs_key ins_key;
-       struct btrfs_extent_item *ei;
-       struct tree_backref *tback;
+       struct btrfs_key key;
+       struct btrfs_root *dest_root;
+       struct extent_backref *back;
        struct data_backref *dback;
-       struct btrfs_tree_block_info *bi;
-
-       if (!back->is_data)
-               rec->max_size = max_t(u64, rec->max_size,
-                                   info->extent_root->nodesize);
-
-       if (!allocated) {
-               u32 item_size = sizeof(*ei);
-
-               if (!back->is_data)
-                       item_size += sizeof(*bi);
-
-               ins_key.objectid = rec->start;
-               ins_key.offset = rec->max_size;
-               ins_key.type = BTRFS_EXTENT_ITEM_KEY;
-
-               ret = btrfs_insert_empty_item(trans, extent_root, path,
-                                       &ins_key, item_size);
-               if (ret)
-                       goto fail;
-
-               leaf = path->nodes[0];
-               ei = btrfs_item_ptr(leaf, path->slots[0],
-                                   struct btrfs_extent_item);
-
-               btrfs_set_extent_refs(leaf, ei, 0);
-               btrfs_set_extent_generation(leaf, ei, rec->generation);
+       struct orphan_data_extent *orphan;
+       struct btrfs_path path;
+       int recorded_data_ref = 0;
+       int ret = 0;
 
-               if (back->is_data) {
-                       btrfs_set_extent_flags(leaf, ei,
-                                              BTRFS_EXTENT_FLAG_DATA);
-               } else {
-                       struct btrfs_disk_key copy_key;;
+       if (rec->metadata)
+               return 1;
+       btrfs_init_path(&path);
+       list_for_each_entry(back, &rec->backrefs, list) {
+               if (back->full_backref || !back->is_data ||
+                   !back->found_extent_tree)
+                       continue;
+               dback = to_data_backref(back);
+               if (dback->found_ref)
+                       continue;
+               key.objectid = dback->root;
+               key.type = BTRFS_ROOT_ITEM_KEY;
+               key.offset = (u64)-1;
 
-                       tback = (struct tree_backref *)back;
-                       bi = (struct btrfs_tree_block_info *)(ei + 1);
-                       memset_extent_buffer(leaf, 0, (unsigned long)bi,
-                                            sizeof(*bi));
+               dest_root = btrfs_read_fs_root(fs_info, &key);
 
-                       btrfs_set_disk_key_objectid(&copy_key,
-                                                   rec->info_objectid);
-                       btrfs_set_disk_key_type(&copy_key, 0);
-                       btrfs_set_disk_key_offset(&copy_key, 0);
+               /* For non-exist root we just skip it */
+               if (IS_ERR(dest_root) || !dest_root)
+                       continue;
 
-                       btrfs_set_tree_block_level(leaf, bi, rec->info_level);
-                       btrfs_set_tree_block_key(leaf, bi, &copy_key);
+               key.objectid = dback->owner;
+               key.type = BTRFS_EXTENT_DATA_KEY;
+               key.offset = dback->offset;
 
-                       btrfs_set_extent_flags(leaf, ei,
-                                              BTRFS_EXTENT_FLAG_TREE_BLOCK | flags);
+               ret = btrfs_search_slot(NULL, dest_root, &key, &path, 0, 0);
+               btrfs_release_path(&path);
+               /*
+                * For ret < 0, it's OK since the fs-tree may be corrupted,
+                * we need to record it for inode/file extent rebuild.
+                * For ret > 0, we record it only for file extent rebuild.
+                * For ret == 0, the file extent exists but only bytenr
+                * mismatch, let the original bytenr fix routine to handle,
+                * don't record it.
+                */
+               if (ret == 0)
+                       continue;
+               ret = 0;
+               orphan = malloc(sizeof(*orphan));
+               if (!orphan) {
+                       ret = -ENOMEM;
+                       goto out;
                }
-
-               btrfs_mark_buffer_dirty(leaf);
-               ret = btrfs_update_block_group(trans, extent_root, rec->start,
-                                              rec->max_size, 1, 0);
-               if (ret)
-                       goto fail;
-               btrfs_release_path(path);
+               INIT_LIST_HEAD(&orphan->list);
+               orphan->root = dback->root;
+               orphan->objectid = dback->owner;
+               orphan->offset = dback->offset;
+               orphan->disk_bytenr = rec->cache.start;
+               orphan->disk_len = rec->cache.size;
+               list_add(&dest_root->orphan_data_extents, &orphan->list);
+               recorded_data_ref = 1;
        }
+out:
+       btrfs_release_path(&path);
+       if (!ret)
+               return !recorded_data_ref;
+       else
+               return ret;
+}
 
-       if (back->is_data) {
-               u64 parent;
-               int i;
-
-               dback = (struct data_backref *)back;
-               if (back->full_backref)
-                       parent = dback->parent;
-               else
-                       parent = 0;
-
-               for (i = 0; i < dback->found_ref; i++) {
-                       /* if parent != 0, we're doing a full backref
-                        * passing BTRFS_FIRST_FREE_OBJECTID as the owner
-                        * just makes the backref allocator create a data
-                        * backref
-                        */
-                       ret = btrfs_inc_extent_ref(trans, info->extent_root,
-                                                  rec->start, rec->max_size,
-                                                  parent,
-                                                  dback->root,
-                                                  parent ?
-                                                  BTRFS_FIRST_FREE_OBJECTID :
-                                                  dback->owner,
-                                                  dback->offset);
-                       if (ret)
-                               break;
-               }
-               fprintf(stderr, "adding new data backref"
-                               " on %llu %s %llu owner %llu"
-                               " offset %llu found %d\n",
-                               (unsigned long long)rec->start,
-                               back->full_backref ?
-                               "parent" : "root",
-                               back->full_backref ?
-                               (unsigned long long)parent :
-                               (unsigned long long)dback->root,
-                               (unsigned long long)dback->owner,
-                               (unsigned long long)dback->offset,
-                               dback->found_ref);
-       } else {
-               u64 parent;
+/*
+ * when an incorrect extent item is found, this will delete
+ * all of the existing entries for it and recreate them
+ * based on what the tree scan found.
+ */
+static int fixup_extent_refs(struct btrfs_fs_info *info,
+                            struct cache_tree *extent_cache,
+                            struct extent_record *rec)
+{
+       struct btrfs_trans_handle *trans = NULL;
+       int ret;
+       struct btrfs_path path;
+       struct list_head *cur = rec->backrefs.next;
+       struct cache_extent *cache;
+       struct extent_backref *back;
+       int allocated = 0;
+       u64 flags = 0;
 
-               tback = (struct tree_backref *)back;
-               if (back->full_backref)
-                       parent = tback->parent;
-               else
-                       parent = 0;
+       if (rec->flag_block_full_backref)
+               flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
 
-               ret = btrfs_inc_extent_ref(trans, info->extent_root,
-                                          rec->start, rec->max_size,
-                                          parent, tback->root, 0, 0);
-               fprintf(stderr, "adding new tree backref on "
-                       "start %llu len %llu parent %llu root %llu\n",
-                       rec->start, rec->max_size, parent, tback->root);
+       btrfs_init_path(&path);
+       if (rec->refs != rec->extent_item_refs && !rec->metadata) {
+               /*
+                * Sometimes the backrefs themselves are so broken they don't
+                * get attached to any meaningful rec, so first go back and
+                * check any of our backrefs that we couldn't find and throw
+                * them into the list if we find the backref so that
+                * verify_backrefs can figure out what to do.
+                */
+               ret = find_possible_backrefs(info, &path, extent_cache, rec);
+               if (ret < 0)
+                       goto out;
        }
-fail:
-       btrfs_release_path(path);
-       return ret;
-}
 
-static struct extent_entry *find_entry(struct list_head *entries,
-                                      u64 bytenr, u64 bytes)
-{
-       struct extent_entry *entry = NULL;
+       /* step one, make sure all of the backrefs agree */
+       ret = verify_backrefs(info, &path, rec);
+       if (ret < 0)
+               goto out;
 
-       list_for_each_entry(entry, entries, list) {
-               if (entry->bytenr == bytenr && entry->bytes == bytes)
-                       return entry;
+       trans = btrfs_start_transaction(info->extent_root, 1);
+       if (IS_ERR(trans)) {
+               ret = PTR_ERR(trans);
+               goto out;
        }
 
-       return NULL;
-}
+       /* step two, delete all the existing records */
+       ret = delete_extent_records(trans, info->extent_root, &path,
+                                   rec->start, rec->max_size);
 
-static struct extent_entry *find_most_right_entry(struct list_head *entries)
-{
-       struct extent_entry *entry, *best = NULL, *prev = NULL;
+       if (ret < 0)
+               goto out;
 
-       list_for_each_entry(entry, entries, list) {
-               if (!prev) {
-                       prev = entry;
-                       continue;
-               }
+       /* was this block corrupt?  If so, don't add references to it */
+       cache = lookup_cache_extent(info->corrupt_blocks,
+                                   rec->start, rec->max_size);
+       if (cache) {
+               ret = 0;
+               goto out;
+       }
 
-               /*
-                * If there are as many broken entries as entries then we know
-                * not to trust this particular entry.
-                */
-               if (entry->broken == entry->count)
-                       continue;
+       /* step three, recreate all the refs we did find */
+       while(cur != &rec->backrefs) {
+               back = to_extent_backref(cur);
+               cur = cur->next;
 
                /*
-                * If our current entry == best then we can't be sure our best
-                * is really the best, so we need to keep searching.
+                * if we didn't find any references, don't create a
+                * new extent record
                 */
-               if (best && best->count == entry->count) {
-                       prev = entry;
-                       best = NULL;
+               if (!back->found_ref)
                        continue;
-               }
 
-               /* Prev == entry, not good enough, have to keep searching */
-               if (!prev->broken && prev->count == entry->count)
-                       continue;
+               rec->bad_full_backref = 0;
+               ret = record_extent(trans, info, &path, rec, back, allocated, flags);
+               allocated = 1;
 
-               if (!best)
-                       best = (prev->count > entry->count) ? prev : entry;
-               else if (best->count < entry->count)
-                       best = entry;
-               prev = entry;
+               if (ret)
+                       goto out;
+       }
+out:
+       if (trans) {
+               int err = btrfs_commit_transaction(trans, info->extent_root);
+               if (!ret)
+                       ret = err;
        }
 
-       return best;
+       btrfs_release_path(&path);
+       return ret;
 }
 
-static int repair_ref(struct btrfs_fs_info *info, struct btrfs_path *path,
-                     struct data_backref *dback, struct extent_entry *entry)
+static int fixup_extent_flags(struct btrfs_fs_info *fs_info,
+                             struct extent_record *rec)
 {
        struct btrfs_trans_handle *trans;
-       struct btrfs_root *root;
-       struct btrfs_file_extent_item *fi;
-       struct extent_buffer *leaf;
+       struct btrfs_root *root = fs_info->extent_root;
+       struct btrfs_path path;
+       struct btrfs_extent_item *ei;
        struct btrfs_key key;
-       u64 bytenr, bytes;
-       int ret, err;
+       u64 flags;
+       int ret = 0;
 
-       key.objectid = dback->root;
-       key.type = BTRFS_ROOT_ITEM_KEY;
-       key.offset = (u64)-1;
-       root = btrfs_read_fs_root(info, &key);
-       if (IS_ERR(root)) {
-               fprintf(stderr, "Couldn't find root for our ref\n");
-               return -EINVAL;
+       key.objectid = rec->start;
+       if (rec->metadata) {
+               key.type = BTRFS_METADATA_ITEM_KEY;
+               key.offset = rec->info_level;
+       } else {
+               key.type = BTRFS_EXTENT_ITEM_KEY;
+               key.offset = rec->max_size;
        }
 
-       /*
-        * The backref points to the original offset of the extent if it was
-        * split, so we need to search down to the offset we have and then walk
-        * forward until we find the backref we're looking for.
-        */
-       key.objectid = dback->owner;
-       key.type = BTRFS_EXTENT_DATA_KEY;
-       key.offset = dback->offset;
-       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       trans = btrfs_start_transaction(root, 0);
+       if (IS_ERR(trans))
+               return PTR_ERR(trans);
+
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(trans, root, &key, &path, 0, 1);
        if (ret < 0) {
-               fprintf(stderr, "Error looking up ref %d\n", ret);
+               btrfs_release_path(&path);
+               btrfs_commit_transaction(trans, root);
                return ret;
+       } else if (ret) {
+               fprintf(stderr, "Didn't find extent for %llu\n",
+                       (unsigned long long)rec->start);
+               btrfs_release_path(&path);
+               btrfs_commit_transaction(trans, root);
+               return -ENOENT;
        }
 
-       while (1) {
-               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-                       ret = btrfs_next_leaf(root, path);
-                       if (ret) {
-                               fprintf(stderr, "Couldn't find our ref, next\n");
-                               return -EINVAL;
-                       }
-               }
-               leaf = path->nodes[0];
-               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
-               if (key.objectid != dback->owner ||
-                   key.type != BTRFS_EXTENT_DATA_KEY) {
-                       fprintf(stderr, "Couldn't find our ref, search\n");
-                       return -EINVAL;
-               }
-               fi = btrfs_item_ptr(leaf, path->slots[0],
-                                   struct btrfs_file_extent_item);
-               bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
-               bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
+       ei = btrfs_item_ptr(path.nodes[0], path.slots[0],
+                           struct btrfs_extent_item);
+       flags = btrfs_extent_flags(path.nodes[0], ei);
+       if (rec->flag_block_full_backref) {
+               fprintf(stderr, "setting full backref on %llu\n",
+                       (unsigned long long)key.objectid);
+               flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
+       } else {
+               fprintf(stderr, "clearing full backref on %llu\n",
+                       (unsigned long long)key.objectid);
+               flags &= ~BTRFS_BLOCK_FLAG_FULL_BACKREF;
+       }
+       btrfs_set_extent_flags(path.nodes[0], ei, flags);
+       btrfs_mark_buffer_dirty(path.nodes[0]);
+       btrfs_release_path(&path);
+       return btrfs_commit_transaction(trans, root);
+}
 
-               if (bytenr == dback->disk_bytenr && bytes == dback->bytes)
-                       break;
-               path->slots[0]++;
+/* right now we only prune from the extent allocation tree */
+static int prune_one_block(struct btrfs_trans_handle *trans,
+                          struct btrfs_fs_info *info,
+                          struct btrfs_corrupt_block *corrupt)
+{
+       int ret;
+       struct btrfs_path path;
+       struct extent_buffer *eb;
+       u64 found;
+       int slot;
+       int nritems;
+       int level = corrupt->level + 1;
+
+       btrfs_init_path(&path);
+again:
+       /* we want to stop at the parent to our busted block */
+       path.lowest_level = level;
+
+       ret = btrfs_search_slot(trans, info->extent_root,
+                               &corrupt->key, &path, -1, 1);
+
+       if (ret < 0)
+               goto out;
+
+       eb = path.nodes[level];
+       if (!eb) {
+               ret = -ENOENT;
+               goto out;
        }
 
-       btrfs_release_path(path);
+       /*
+        * hopefully the search gave us the block we want to prune,
+        * lets try that first
+        */
+       slot = path.slots[level];
+       found =  btrfs_node_blockptr(eb, slot);
+       if (found == corrupt->cache.start)
+               goto del_ptr;
 
-       trans = btrfs_start_transaction(root, 1);
-       if (IS_ERR(trans))
-               return PTR_ERR(trans);
+       nritems = btrfs_header_nritems(eb);
 
+       /* the search failed, lets scan this node and hope we find it */
+       for (slot = 0; slot < nritems; slot++) {
+               found =  btrfs_node_blockptr(eb, slot);
+               if (found == corrupt->cache.start)
+                       goto del_ptr;
+       }
        /*
-        * Ok we have the key of the file extent we want to fix, now we can cow
-        * down to the thing and fix it.
+        * we couldn't find the bad block.  TODO, search all the nodes for pointers
+        * to this block
         */
-       ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
-       if (ret < 0) {
-               fprintf(stderr, "Error cowing down to ref [%Lu, %u, %Lu]: %d\n",
-                       key.objectid, key.type, key.offset, ret);
+       if (eb == info->extent_root->node) {
+               ret = -ENOENT;
                goto out;
+       } else {
+               level++;
+               btrfs_release_path(&path);
+               goto again;
        }
-       if (ret > 0) {
-               fprintf(stderr, "Well that's odd, we just found this key "
-                       "[%Lu, %u, %Lu]\n", key.objectid, key.type,
-                       key.offset);
-               ret = -EINVAL;
-               goto out;
+
+del_ptr:
+       printk("deleting pointer to block %Lu\n", corrupt->cache.start);
+       ret = btrfs_del_ptr(trans, info->extent_root, &path, level, slot);
+
+out:
+       btrfs_release_path(&path);
+       return ret;
+}
+
+static int prune_corrupt_blocks(struct btrfs_fs_info *info)
+{
+       struct btrfs_trans_handle *trans = NULL;
+       struct cache_extent *cache;
+       struct btrfs_corrupt_block *corrupt;
+
+       while (1) {
+               cache = search_cache_extent(info->corrupt_blocks, 0);
+               if (!cache)
+                       break;
+               if (!trans) {
+                       trans = btrfs_start_transaction(info->extent_root, 1);
+                       if (IS_ERR(trans))
+                               return PTR_ERR(trans);
+               }
+               corrupt = container_of(cache, struct btrfs_corrupt_block, cache);
+               prune_one_block(trans, info, corrupt);
+               remove_cache_extent(info->corrupt_blocks, cache);
+       }
+       if (trans)
+               return btrfs_commit_transaction(trans, info->extent_root);
+       return 0;
+}
+
+static void reset_cached_block_groups(struct btrfs_fs_info *fs_info)
+{
+       struct btrfs_block_group_cache *cache;
+       u64 start, end;
+       int ret;
+
+       while (1) {
+               ret = find_first_extent_bit(&fs_info->free_space_cache, 0,
+                                           &start, &end, EXTENT_DIRTY);
+               if (ret)
+                       break;
+               clear_extent_dirty(&fs_info->free_space_cache, start, end,
+                                  GFP_NOFS);
        }
-       leaf = path->nodes[0];
-       fi = btrfs_item_ptr(leaf, path->slots[0],
-                           struct btrfs_file_extent_item);
 
-       if (btrfs_file_extent_compression(leaf, fi) &&
-           dback->disk_bytenr != entry->bytenr) {
-               fprintf(stderr, "Ref doesn't match the record start and is "
-                       "compressed, please take a btrfs-image of this file "
-                       "system and send it to a btrfs developer so they can "
-                       "complete this functionality for bytenr %Lu\n",
-                       dback->disk_bytenr);
-               ret = -EINVAL;
-               goto out;
+       start = 0;
+       while (1) {
+               cache = btrfs_lookup_first_block_group(fs_info, start);
+               if (!cache)
+                       break;
+               if (cache->cached)
+                       cache->cached = 0;
+               start = cache->key.objectid + cache->key.offset;
        }
+}
 
-       if (dback->node.broken && dback->disk_bytenr != entry->bytenr) {
-               btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
-       } else if (dback->disk_bytenr > entry->bytenr) {
-               u64 off_diff, offset;
+static int check_extent_refs(struct btrfs_root *root,
+                            struct cache_tree *extent_cache)
+{
+       struct extent_record *rec;
+       struct cache_extent *cache;
+       int err = 0;
+       int ret = 0;
+       int fixed = 0;
+       int had_dups = 0;
+       int recorded = 0;
 
-               off_diff = dback->disk_bytenr - entry->bytenr;
-               offset = btrfs_file_extent_offset(leaf, fi);
-               if (dback->disk_bytenr + offset +
-                   btrfs_file_extent_num_bytes(leaf, fi) >
-                   entry->bytenr + entry->bytes) {
-                       fprintf(stderr, "Ref is past the entry end, please "
-                               "take a btrfs-image of this file system and "
-                               "send it to a btrfs developer, ref %Lu\n",
-                               dback->disk_bytenr);
-                       ret = -EINVAL;
-                       goto out;
+       if (repair) {
+               /*
+                * if we're doing a repair, we have to make sure
+                * we don't allocate from the problem extents.
+                * In the worst case, this will be all the
+                * extents in the FS
+                */
+               cache = search_cache_extent(extent_cache, 0);
+               while(cache) {
+                       rec = container_of(cache, struct extent_record, cache);
+                       set_extent_dirty(root->fs_info->excluded_extents,
+                                        rec->start,
+                                        rec->start + rec->max_size - 1,
+                                        GFP_NOFS);
+                       cache = next_cache_extent(cache);
                }
-               offset += off_diff;
-               btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
-               btrfs_set_file_extent_offset(leaf, fi, offset);
-       } else if (dback->disk_bytenr < entry->bytenr) {
-               u64 offset;
 
-               offset = btrfs_file_extent_offset(leaf, fi);
-               if (dback->disk_bytenr + offset < entry->bytenr) {
-                       fprintf(stderr, "Ref is before the entry start, please"
-                               " take a btrfs-image of this file system and "
-                               "send it to a btrfs developer, ref %Lu\n",
-                               dback->disk_bytenr);
-                       ret = -EINVAL;
-                       goto out;
+               /* pin down all the corrupted blocks too */
+               cache = search_cache_extent(root->fs_info->corrupt_blocks, 0);
+               while(cache) {
+                       set_extent_dirty(root->fs_info->excluded_extents,
+                                        cache->start,
+                                        cache->start + cache->size - 1,
+                                        GFP_NOFS);
+                       cache = next_cache_extent(cache);
                }
-
-               offset += dback->disk_bytenr;
-               offset -= entry->bytenr;
-               btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
-               btrfs_set_file_extent_offset(leaf, fi, offset);
+               prune_corrupt_blocks(root->fs_info);
+               reset_cached_block_groups(root->fs_info);
        }
 
-       btrfs_set_file_extent_disk_num_bytes(leaf, fi, entry->bytes);
-
-       /*
-        * Chances are if disk_num_bytes were wrong then so is ram_bytes, but
-        * only do this if we aren't using compression, otherwise it's a
-        * trickier case.
-        */
-       if (!btrfs_file_extent_compression(leaf, fi))
-               btrfs_set_file_extent_ram_bytes(leaf, fi, entry->bytes);
-       else
-               printf("ram bytes may be wrong?\n");
-       btrfs_mark_buffer_dirty(leaf);
-out:
-       err = btrfs_commit_transaction(trans, root);
-       btrfs_release_path(path);
-       return ret ? ret : err;
-}
-
-static int verify_backrefs(struct btrfs_fs_info *info, struct btrfs_path *path,
-                          struct extent_record *rec)
-{
-       struct extent_backref *back;
-       struct data_backref *dback;
-       struct extent_entry *entry, *best = NULL;
-       LIST_HEAD(entries);
-       int nr_entries = 0;
-       int broken_entries = 0;
-       int ret = 0;
-       short mismatch = 0;
+       reset_cached_block_groups(root->fs_info);
 
        /*
-        * Metadata is easy and the backrefs should always agree on bytenr and
-        * size, if not we've got bigger issues.
+        * We need to delete any duplicate entries we find first otherwise we
+        * could mess up the extent tree when we have backrefs that actually
+        * belong to a different extent item and not the weird duplicate one.
         */
-       if (rec->metadata)
-               return 0;
-
-       list_for_each_entry(back, &rec->backrefs, list) {
-               if (back->full_backref || !back->is_data)
-                       continue;
-
-               dback = (struct data_backref *)back;
+       while (repair && !list_empty(&duplicate_extents)) {
+               rec = to_extent_record(duplicate_extents.next);
+               list_del_init(&rec->list);
 
-               /*
-                * We only pay attention to backrefs that we found a real
-                * backref for.
+               /* Sometimes we can find a backref before we find an actual
+                * extent, so we need to process it a little bit to see if there
+                * truly are multiple EXTENT_ITEM_KEY's for the same range, or
+                * if this is a backref screwup.  If we need to delete stuff
+                * process_duplicates() will return 0, otherwise it will return
+                * 1 and we
                 */
-               if (dback->found_ref == 0)
+               if (process_duplicates(root, extent_cache, rec))
                        continue;
-
+               ret = delete_duplicate_records(root, rec);
+               if (ret < 0)
+                       return ret;
                /*
-                * For now we only catch when the bytes don't match, not the
-                * bytenr.  We can easily do this at the same time, but I want
-                * to have a fs image to test on before we just add repair
-                * functionality willy-nilly so we know we won't screw up the
-                * repair.
+                * delete_duplicate_records will return the number of entries
+                * deleted, so if it's greater than 0 then we know we actually
+                * did something and we need to remove.
                 */
+               if (ret)
+                       had_dups = 1;
+       }
 
-               entry = find_entry(&entries, dback->disk_bytenr,
-                                  dback->bytes);
-               if (!entry) {
-                       entry = malloc(sizeof(struct extent_entry));
-                       if (!entry) {
-                               ret = -ENOMEM;
-                               goto out;
+       if (had_dups)
+               return -EAGAIN;
+
+       while(1) {
+               int cur_err = 0;
+
+               fixed = 0;
+               recorded = 0;
+               cache = search_cache_extent(extent_cache, 0);
+               if (!cache)
+                       break;
+               rec = container_of(cache, struct extent_record, cache);
+               if (rec->num_duplicates) {
+                       fprintf(stderr, "extent item %llu has multiple extent "
+                               "items\n", (unsigned long long)rec->start);
+                       err = 1;
+                       cur_err = 1;
+               }
+
+               if (rec->refs != rec->extent_item_refs) {
+                       fprintf(stderr, "ref mismatch on [%llu %llu] ",
+                               (unsigned long long)rec->start,
+                               (unsigned long long)rec->nr);
+                       fprintf(stderr, "extent item %llu, found %llu\n",
+                               (unsigned long long)rec->extent_item_refs,
+                               (unsigned long long)rec->refs);
+                       ret = record_orphan_data_extents(root->fs_info, rec);
+                       if (ret < 0)
+                               goto repair_abort;
+                       if (ret == 0) {
+                               recorded = 1;
+                       } else {
+                               /*
+                                * we can't use the extent to repair file
+                                * extent, let the fallback method handle it.
+                                */
+                               if (!fixed && repair) {
+                                       ret = fixup_extent_refs(
+                                                       root->fs_info,
+                                                       extent_cache, rec);
+                                       if (ret)
+                                               goto repair_abort;
+                                       fixed = 1;
+                               }
                        }
-                       memset(entry, 0, sizeof(*entry));
-                       entry->bytenr = dback->disk_bytenr;
-                       entry->bytes = dback->bytes;
-                       list_add_tail(&entry->list, &entries);
-                       nr_entries++;
+                       err = 1;
+                       cur_err = 1;
+               }
+               if (all_backpointers_checked(rec, 1)) {
+                       fprintf(stderr, "backpointer mismatch on [%llu %llu]\n",
+                               (unsigned long long)rec->start,
+                               (unsigned long long)rec->nr);
+
+                       if (!fixed && !recorded && repair) {
+                               ret = fixup_extent_refs(root->fs_info,
+                                                       extent_cache, rec);
+                               if (ret)
+                                       goto repair_abort;
+                               fixed = 1;
+                       }
+                       cur_err = 1;
+                       err = 1;
+               }
+               if (!rec->owner_ref_checked) {
+                       fprintf(stderr, "owner ref check failed [%llu %llu]\n",
+                               (unsigned long long)rec->start,
+                               (unsigned long long)rec->nr);
+                       if (!fixed && !recorded && repair) {
+                               ret = fixup_extent_refs(root->fs_info,
+                                                       extent_cache, rec);
+                               if (ret)
+                                       goto repair_abort;
+                               fixed = 1;
+                       }
+                       err = 1;
+                       cur_err = 1;
+               }
+               if (rec->bad_full_backref) {
+                       fprintf(stderr, "bad full backref, on [%llu]\n",
+                               (unsigned long long)rec->start);
+                       if (repair) {
+                               ret = fixup_extent_flags(root->fs_info, rec);
+                               if (ret)
+                                       goto repair_abort;
+                               fixed = 1;
+                       }
+                       err = 1;
+                       cur_err = 1;
                }
-
                /*
-                * If we only have on entry we may think the entries agree when
-                * in reality they don't so we have to do some extra checking.
+                * Although it's not a extent ref's problem, we reuse this
+                * routine for error reporting.
+                * No repair function yet.
                 */
-               if (dback->disk_bytenr != rec->start ||
-                   dback->bytes != rec->nr || back->broken)
-                       mismatch = 1;
+               if (rec->crossing_stripes) {
+                       fprintf(stderr,
+                               "bad metadata [%llu, %llu) crossing stripe boundary\n",
+                               rec->start, rec->start + rec->max_size);
+                       err = 1;
+                       cur_err = 1;
+               }
 
-               if (back->broken) {
-                       entry->broken++;
-                       broken_entries++;
+               if (rec->wrong_chunk_type) {
+                       fprintf(stderr,
+                               "bad extent [%llu, %llu), type mismatch with chunk\n",
+                               rec->start, rec->start + rec->max_size);
+                       err = 1;
+                       cur_err = 1;
                }
 
-               entry->count++;
+               remove_cache_extent(extent_cache, cache);
+               free_all_extent_backrefs(rec);
+               if (!init_extent_tree && repair && (!cur_err || fixed))
+                       clear_extent_dirty(root->fs_info->excluded_extents,
+                                          rec->start,
+                                          rec->start + rec->max_size - 1,
+                                          GFP_NOFS);
+               free(rec);
        }
+repair_abort:
+       if (repair) {
+               if (ret && ret != -EAGAIN) {
+                       fprintf(stderr, "failed to repair damaged filesystem, aborting\n");
+                       exit(1);
+               } else if (!ret) {
+                       struct btrfs_trans_handle *trans;
 
-       /* Yay all the backrefs agree, carry on good sir */
-       if (nr_entries <= 1 && !mismatch)
-               goto out;
+                       root = root->fs_info->extent_root;
+                       trans = btrfs_start_transaction(root, 1);
+                       if (IS_ERR(trans)) {
+                               ret = PTR_ERR(trans);
+                               goto repair_abort;
+                       }
 
-       fprintf(stderr, "attempting to repair backref discrepency for bytenr "
-               "%Lu\n", rec->start);
+                       btrfs_fix_block_accounting(trans, root);
+                       ret = btrfs_commit_transaction(trans, root);
+                       if (ret)
+                               goto repair_abort;
+               }
+               if (err)
+                       fprintf(stderr, "repaired damaged extent references\n");
+               return ret;
+       }
+       return err;
+}
 
-       /*
-        * First we want to see if the backrefs can agree amongst themselves who
-        * is right, so figure out which one of the entries has the highest
-        * count.
-        */
-       best = find_most_right_entry(&entries);
+u64 calc_stripe_length(u64 type, u64 length, int num_stripes)
+{
+       u64 stripe_size;
 
-       /*
-        * Ok so we may have an even split between what the backrefs think, so
-        * this is where we use the extent ref to see what it thinks.
-        */
-       if (!best) {
-               entry = find_entry(&entries, rec->start, rec->nr);
-               if (!entry && (!broken_entries || !rec->found_rec)) {
-                       fprintf(stderr, "Backrefs don't agree with each other "
-                               "and extent record doesn't agree with anybody,"
-                               " so we can't fix bytenr %Lu bytes %Lu\n",
-                               rec->start, rec->nr);
-                       ret = -EINVAL;
-                       goto out;
-               } else if (!entry) {
-                       /*
-                        * Ok our backrefs were broken, we'll assume this is the
-                        * correct value and add an entry for this range.
-                        */
-                       entry = malloc(sizeof(struct extent_entry));
-                       if (!entry) {
-                               ret = -ENOMEM;
-                               goto out;
-                       }
-                       memset(entry, 0, sizeof(*entry));
-                       entry->bytenr = rec->start;
-                       entry->bytes = rec->nr;
-                       list_add_tail(&entry->list, &entries);
-                       nr_entries++;
-               }
-               entry->count++;
-               best = find_most_right_entry(&entries);
-               if (!best) {
-                       fprintf(stderr, "Backrefs and extent record evenly "
-                               "split on who is right, this is going to "
-                               "require user input to fix bytenr %Lu bytes "
-                               "%Lu\n", rec->start, rec->nr);
-                       ret = -EINVAL;
-                       goto out;
-               }
+       if (type & BTRFS_BLOCK_GROUP_RAID0) {
+               stripe_size = length;
+               stripe_size /= num_stripes;
+       } else if (type & BTRFS_BLOCK_GROUP_RAID10) {
+               stripe_size = length * 2;
+               stripe_size /= num_stripes;
+       } else if (type & BTRFS_BLOCK_GROUP_RAID5) {
+               stripe_size = length;
+               stripe_size /= (num_stripes - 1);
+       } else if (type & BTRFS_BLOCK_GROUP_RAID6) {
+               stripe_size = length;
+               stripe_size /= (num_stripes - 2);
+       } else {
+               stripe_size = length;
        }
+       return stripe_size;
+}
 
-       /*
-        * I don't think this can happen currently as we'll abort() if we catch
-        * this case higher up, but in case somebody removes that we still can't
-        * deal with it properly here yet, so just bail out of that's the case.
-        */
-       if (best->bytenr != rec->start) {
-               fprintf(stderr, "Extent start and backref starts don't match, "
-                       "please use btrfs-image on this file system and send "
-                       "it to a btrfs developer so they can make fsck fix "
-                       "this particular case.  bytenr is %Lu, bytes is %Lu\n",
-                       rec->start, rec->nr);
-               ret = -EINVAL;
-               goto out;
+/*
+ * Check the chunk with its block group/dev list ref:
+ * Return 0 if all refs seems valid.
+ * Return 1 if part of refs seems valid, need later check for rebuild ref
+ * like missing block group and needs to search extent tree to rebuild them.
+ * Return -1 if essential refs are missing and unable to rebuild.
+ */
+static int check_chunk_refs(struct chunk_record *chunk_rec,
+                           struct block_group_tree *block_group_cache,
+                           struct device_extent_tree *dev_extent_cache,
+                           int silent)
+{
+       struct cache_extent *block_group_item;
+       struct block_group_record *block_group_rec;
+       struct cache_extent *dev_extent_item;
+       struct device_extent_record *dev_extent_rec;
+       u64 devid;
+       u64 offset;
+       u64 length;
+       int metadump_v2 = 0;
+       int i;
+       int ret = 0;
+
+       block_group_item = lookup_cache_extent(&block_group_cache->tree,
+                                              chunk_rec->offset,
+                                              chunk_rec->length);
+       if (block_group_item) {
+               block_group_rec = container_of(block_group_item,
+                                              struct block_group_record,
+                                              cache);
+               if (chunk_rec->length != block_group_rec->offset ||
+                   chunk_rec->offset != block_group_rec->objectid ||
+                   (!metadump_v2 &&
+                    chunk_rec->type_flags != block_group_rec->flags)) {
+                       if (!silent)
+                               fprintf(stderr,
+                                       "Chunk[%llu, %u, %llu]: length(%llu), offset(%llu), type(%llu) mismatch with block group[%llu, %u, %llu]: offset(%llu), objectid(%llu), flags(%llu)\n",
+                                       chunk_rec->objectid,
+                                       chunk_rec->type,
+                                       chunk_rec->offset,
+                                       chunk_rec->length,
+                                       chunk_rec->offset,
+                                       chunk_rec->type_flags,
+                                       block_group_rec->objectid,
+                                       block_group_rec->type,
+                                       block_group_rec->offset,
+                                       block_group_rec->offset,
+                                       block_group_rec->objectid,
+                                       block_group_rec->flags);
+                       ret = -1;
+               } else {
+                       list_del_init(&block_group_rec->list);
+                       chunk_rec->bg_rec = block_group_rec;
+               }
+       } else {
+               if (!silent)
+                       fprintf(stderr,
+                               "Chunk[%llu, %u, %llu]: length(%llu), offset(%llu), type(%llu) is not found in block group\n",
+                               chunk_rec->objectid,
+                               chunk_rec->type,
+                               chunk_rec->offset,
+                               chunk_rec->length,
+                               chunk_rec->offset,
+                               chunk_rec->type_flags);
+               ret = 1;
        }
 
-       /*
-        * Ok great we all agreed on an extent record, let's go find the real
-        * references and fix up the ones that don't match.
-        */
-       list_for_each_entry(back, &rec->backrefs, list) {
-               if (back->full_backref || !back->is_data)
-                       continue;
+       if (metadump_v2)
+               return ret;
 
-               dback = (struct data_backref *)back;
+       length = calc_stripe_length(chunk_rec->type_flags, chunk_rec->length,
+                                   chunk_rec->num_stripes);
+       for (i = 0; i < chunk_rec->num_stripes; ++i) {
+               devid = chunk_rec->stripes[i].devid;
+               offset = chunk_rec->stripes[i].offset;
+               dev_extent_item = lookup_cache_extent2(&dev_extent_cache->tree,
+                                                      devid, offset, length);
+               if (dev_extent_item) {
+                       dev_extent_rec = container_of(dev_extent_item,
+                                               struct device_extent_record,
+                                               cache);
+                       if (dev_extent_rec->objectid != devid ||
+                           dev_extent_rec->offset != offset ||
+                           dev_extent_rec->chunk_offset != chunk_rec->offset ||
+                           dev_extent_rec->length != length) {
+                               if (!silent)
+                                       fprintf(stderr,
+                                               "Chunk[%llu, %u, %llu] stripe[%llu, %llu] dismatch dev extent[%llu, %llu, %llu]\n",
+                                               chunk_rec->objectid,
+                                               chunk_rec->type,
+                                               chunk_rec->offset,
+                                               chunk_rec->stripes[i].devid,
+                                               chunk_rec->stripes[i].offset,
+                                               dev_extent_rec->objectid,
+                                               dev_extent_rec->offset,
+                                               dev_extent_rec->length);
+                               ret = -1;
+                       } else {
+                               list_move(&dev_extent_rec->chunk_list,
+                                         &chunk_rec->dextents);
+                       }
+               } else {
+                       if (!silent)
+                               fprintf(stderr,
+                                       "Chunk[%llu, %u, %llu] stripe[%llu, %llu] is not found in dev extent\n",
+                                       chunk_rec->objectid,
+                                       chunk_rec->type,
+                                       chunk_rec->offset,
+                                       chunk_rec->stripes[i].devid,
+                                       chunk_rec->stripes[i].offset);
+                       ret = -1;
+               }
+       }
+       return ret;
+}
 
-               /*
-                * Still ignoring backrefs that don't have a real ref attached
-                * to them.
-                */
-               if (dback->found_ref == 0)
-                       continue;
+/* check btrfs_chunk -> btrfs_dev_extent / btrfs_block_group_item */
+int check_chunks(struct cache_tree *chunk_cache,
+                struct block_group_tree *block_group_cache,
+                struct device_extent_tree *dev_extent_cache,
+                struct list_head *good, struct list_head *bad,
+                struct list_head *rebuild, int silent)
+{
+       struct cache_extent *chunk_item;
+       struct chunk_record *chunk_rec;
+       struct block_group_record *bg_rec;
+       struct device_extent_record *dext_rec;
+       int err;
+       int ret = 0;
 
-               if (dback->bytes == best->bytes &&
-                   dback->disk_bytenr == best->bytenr)
-                       continue;
+       chunk_item = first_cache_extent(chunk_cache);
+       while (chunk_item) {
+               chunk_rec = container_of(chunk_item, struct chunk_record,
+                                        cache);
+               err = check_chunk_refs(chunk_rec, block_group_cache,
+                                      dev_extent_cache, silent);
+               if (err < 0)
+                       ret = err;
+               if (err == 0 && good)
+                       list_add_tail(&chunk_rec->list, good);
+               if (err > 0 && rebuild)
+                       list_add_tail(&chunk_rec->list, rebuild);
+               if (err < 0 && bad)
+                       list_add_tail(&chunk_rec->list, bad);
+               chunk_item = next_cache_extent(chunk_item);
+       }
 
-               ret = repair_ref(info, path, dback, best);
-               if (ret)
-                       goto out;
+       list_for_each_entry(bg_rec, &block_group_cache->block_groups, list) {
+               if (!silent)
+                       fprintf(stderr,
+                               "Block group[%llu, %llu] (flags = %llu) didn't find the relative chunk.\n",
+                               bg_rec->objectid,
+                               bg_rec->offset,
+                               bg_rec->flags);
+               if (!ret)
+                       ret = 1;
        }
 
-       /*
-        * Ok we messed with the actual refs, which means we need to drop our
-        * entire cache and go back and rescan.  I know this is a huge pain and
-        * adds a lot of extra work, but it's the only way to be safe.  Once all
-        * the backrefs agree we may not need to do anything to the extent
-        * record itself.
-        */
-       ret = -EAGAIN;
-out:
-       while (!list_empty(&entries)) {
-               entry = list_entry(entries.next, struct extent_entry, list);
-               list_del_init(&entry->list);
-               free(entry);
+       list_for_each_entry(dext_rec, &dev_extent_cache->no_chunk_orphans,
+                           chunk_list) {
+               if (!silent)
+                       fprintf(stderr,
+                               "Device extent[%llu, %llu, %llu] didn't find the relative chunk.\n",
+                               dext_rec->objectid,
+                               dext_rec->offset,
+                               dext_rec->length);
+               if (!ret)
+                       ret = 1;
        }
        return ret;
 }
 
-static int process_duplicates(struct btrfs_root *root,
-                             struct cache_tree *extent_cache,
-                             struct extent_record *rec)
+
+static int check_device_used(struct device_record *dev_rec,
+                            struct device_extent_tree *dext_cache)
 {
-       struct extent_record *good, *tmp;
        struct cache_extent *cache;
-       int ret;
-
-       /*
-        * If we found a extent record for this extent then return, or if we
-        * have more than one duplicate we are likely going to need to delete
-        * something.
-        */
-       if (rec->found_rec || rec->num_duplicates > 1)
-               return 0;
-
-       /* Shouldn't happen but just in case */
-       BUG_ON(!rec->num_duplicates);
-
-       /*
-        * So this happens if we end up with a backref that doesn't match the
-        * actual extent entry.  So either the backref is bad or the extent
-        * entry is bad.  Either way we want to have the extent_record actually
-        * reflect what we found in the extent_tree, so we need to take the
-        * duplicate out and use that as the extent_record since the only way we
-        * get a duplicate is if we find a real life BTRFS_EXTENT_ITEM_KEY.
-        */
-       remove_cache_extent(extent_cache, &rec->cache);
+       struct device_extent_record *dev_extent_rec;
+       u64 total_byte = 0;
 
-       good = list_entry(rec->dups.next, struct extent_record, list);
-       list_del_init(&good->list);
-       INIT_LIST_HEAD(&good->backrefs);
-       INIT_LIST_HEAD(&good->dups);
-       good->cache.start = good->start;
-       good->cache.size = good->nr;
-       good->content_checked = 0;
-       good->owner_ref_checked = 0;
-       good->num_duplicates = 0;
-       good->refs = rec->refs;
-       list_splice_init(&rec->backrefs, &good->backrefs);
-       while (1) {
-               cache = lookup_cache_extent(extent_cache, good->start,
-                                           good->nr);
-               if (!cache)
+       cache = search_cache_extent2(&dext_cache->tree, dev_rec->devid, 0);
+       while (cache) {
+               dev_extent_rec = container_of(cache,
+                                             struct device_extent_record,
+                                             cache);
+               if (dev_extent_rec->objectid != dev_rec->devid)
                        break;
-               tmp = container_of(cache, struct extent_record, cache);
 
-               /*
-                * If we find another overlapping extent and it's found_rec is
-                * set then it's a duplicate and we need to try and delete
-                * something.
-                */
-               if (tmp->found_rec || tmp->num_duplicates > 0) {
-                       if (list_empty(&good->list))
-                               list_add_tail(&good->list,
-                                             &duplicate_extents);
-                       good->num_duplicates += tmp->num_duplicates + 1;
-                       list_splice_init(&tmp->dups, &good->dups);
-                       list_del_init(&tmp->list);
-                       list_add_tail(&tmp->list, &good->dups);
-                       remove_cache_extent(extent_cache, &tmp->cache);
-                       continue;
-               }
+               list_del_init(&dev_extent_rec->device_list);
+               total_byte += dev_extent_rec->length;
+               cache = next_cache_extent(cache);
+       }
 
-               /*
-                * Ok we have another non extent item backed extent rec, so lets
-                * just add it to this extent and carry on like we did above.
-                */
-               good->refs += tmp->refs;
-               list_splice_init(&tmp->backrefs, &good->backrefs);
-               remove_cache_extent(extent_cache, &tmp->cache);
-               free(tmp);
+       if (total_byte != dev_rec->byte_used) {
+               fprintf(stderr,
+                       "Dev extent's total-byte(%llu) is not equal to byte-used(%llu) in dev[%llu, %u, %llu]\n",
+                       total_byte, dev_rec->byte_used, dev_rec->objectid,
+                       dev_rec->type, dev_rec->offset);
+               return -1;
+       } else {
+               return 0;
        }
-       ret = insert_cache_extent(extent_cache, &good->cache);
-       BUG_ON(ret);
-       free(rec);
-       return good->num_duplicates ? 0 : 1;
 }
 
-static int delete_duplicate_records(struct btrfs_root *root,
-                                   struct extent_record *rec)
+/* check btrfs_dev_item -> btrfs_dev_extent */
+static int check_devices(struct rb_root *dev_cache,
+                        struct device_extent_tree *dev_extent_cache)
 {
-       struct btrfs_trans_handle *trans;
-       LIST_HEAD(delete_list);
-       struct btrfs_path *path;
-       struct extent_record *tmp, *good, *n;
-       int nr_del = 0;
-       int ret = 0, err;
-       struct btrfs_key key;
+       struct rb_node *dev_node;
+       struct device_record *dev_rec;
+       struct device_extent_record *dext_rec;
+       int err;
+       int ret = 0;
 
-       path = btrfs_alloc_path();
-       if (!path) {
-               ret = -ENOMEM;
-               goto out;
+       dev_node = rb_first(dev_cache);
+       while (dev_node) {
+               dev_rec = container_of(dev_node, struct device_record, node);
+               err = check_device_used(dev_rec, dev_extent_cache);
+               if (err)
+                       ret = err;
+
+               dev_node = rb_next(dev_node);
+       }
+       list_for_each_entry(dext_rec, &dev_extent_cache->no_device_orphans,
+                           device_list) {
+               fprintf(stderr,
+                       "Device extent[%llu, %llu, %llu] didn't find its device.\n",
+                       dext_rec->objectid, dext_rec->offset, dext_rec->length);
+               if (!ret)
+                       ret = 1;
        }
+       return ret;
+}
 
-       good = rec;
-       /* Find the record that covers all of the duplicates. */
-       list_for_each_entry(tmp, &rec->dups, list) {
-               if (good->start < tmp->start)
-                       continue;
-               if (good->nr > tmp->nr)
-                       continue;
+static int add_root_item_to_list(struct list_head *head,
+                                 u64 objectid, u64 bytenr, u64 last_snapshot,
+                                 u8 level, u8 drop_level,
+                                 int level_size, struct btrfs_key *drop_key)
+{
 
-               if (tmp->start + tmp->nr < good->start + good->nr) {
-                       fprintf(stderr, "Ok we have overlapping extents that "
-                               "aren't completely covered by eachother, this "
-                               "is going to require more careful thought.  "
-                               "The extents are [%Lu-%Lu] and [%Lu-%Lu]\n",
-                               tmp->start, tmp->nr, good->start, good->nr);
-                       abort();
-               }
-               good = tmp;
-       }
+       struct root_item_record *ri_rec;
+       ri_rec = malloc(sizeof(*ri_rec));
+       if (!ri_rec)
+               return -ENOMEM;
+       ri_rec->bytenr = bytenr;
+       ri_rec->objectid = objectid;
+       ri_rec->level = level;
+       ri_rec->level_size = level_size;
+       ri_rec->drop_level = drop_level;
+       ri_rec->last_snapshot = last_snapshot;
+       if (drop_key)
+               memcpy(&ri_rec->drop_key, drop_key, sizeof(*drop_key));
+       list_add_tail(&ri_rec->list, head);
 
-       if (good != rec)
-               list_add_tail(&rec->list, &delete_list);
+       return 0;
+}
 
-       list_for_each_entry_safe(tmp, n, &rec->dups, list) {
-               if (tmp == good)
-                       continue;
-               list_move_tail(&tmp->list, &delete_list);
-       }
+static void free_root_item_list(struct list_head *list)
+{
+       struct root_item_record *ri_rec;
 
-       root = root->fs_info->extent_root;
-       trans = btrfs_start_transaction(root, 1);
-       if (IS_ERR(trans)) {
-               ret = PTR_ERR(trans);
-               goto out;
+       while (!list_empty(list)) {
+               ri_rec = list_first_entry(list, struct root_item_record,
+                                         list);
+               list_del_init(&ri_rec->list);
+               free(ri_rec);
        }
+}
 
-       list_for_each_entry(tmp, &delete_list, list) {
-               if (tmp->found_rec == 0)
-                       continue;
-               key.objectid = tmp->start;
-               key.type = BTRFS_EXTENT_ITEM_KEY;
-               key.offset = tmp->nr;
+static int deal_root_from_list(struct list_head *list,
+                              struct btrfs_root *root,
+                              struct block_info *bits,
+                              int bits_nr,
+                              struct cache_tree *pending,
+                              struct cache_tree *seen,
+                              struct cache_tree *reada,
+                              struct cache_tree *nodes,
+                              struct cache_tree *extent_cache,
+                              struct cache_tree *chunk_cache,
+                              struct rb_root *dev_cache,
+                              struct block_group_tree *block_group_cache,
+                              struct device_extent_tree *dev_extent_cache)
+{
+       int ret = 0;
+       u64 last;
 
-               /* Shouldn't happen but just in case */
-               if (tmp->metadata) {
-                       fprintf(stderr, "Well this shouldn't happen, extent "
-                               "record overlaps but is metadata? "
-                               "[%Lu, %Lu]\n", tmp->start, tmp->nr);
-                       abort();
+       while (!list_empty(list)) {
+               struct root_item_record *rec;
+               struct extent_buffer *buf;
+               rec = list_entry(list->next,
+                                struct root_item_record, list);
+               last = 0;
+               buf = read_tree_block(root->fs_info->tree_root,
+                                     rec->bytenr, rec->level_size, 0);
+               if (!extent_buffer_uptodate(buf)) {
+                       free_extent_buffer(buf);
+                       ret = -EIO;
+                       break;
                }
-
-               ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
-               if (ret) {
-                       if (ret > 0)
-                               ret = -EINVAL;
+               ret = add_root_to_pending(buf, extent_cache, pending,
+                                   seen, nodes, rec->objectid);
+               if (ret < 0)
                        break;
+               /*
+                * To rebuild extent tree, we need deal with snapshot
+                * one by one, otherwise we deal with node firstly which
+                * can maximize readahead.
+                */
+               while (1) {
+                       ret = run_next_block(root, bits, bits_nr, &last,
+                                            pending, seen, reada, nodes,
+                                            extent_cache, chunk_cache,
+                                            dev_cache, block_group_cache,
+                                            dev_extent_cache, rec);
+                       if (ret != 0)
+                               break;
                }
-               ret = btrfs_del_item(trans, root, path);
-               if (ret)
+               free_extent_buffer(buf);
+               list_del(&rec->list);
+               free(rec);
+               if (ret < 0)
                        break;
-               btrfs_release_path(path);
-               nr_del++;
-       }
-       err = btrfs_commit_transaction(trans, root);
-       if (err && !ret)
-               ret = err;
-out:
-       while (!list_empty(&delete_list)) {
-               tmp = list_entry(delete_list.next, struct extent_record, list);
-               list_del_init(&tmp->list);
-               if (tmp == rec)
-                       continue;
-               free(tmp);
        }
-
-       while (!list_empty(&rec->dups)) {
-               tmp = list_entry(rec->dups.next, struct extent_record, list);
-               list_del_init(&tmp->list);
-               free(tmp);
+       while (ret >= 0) {
+               ret = run_next_block(root, bits, bits_nr, &last, pending, seen,
+                                    reada, nodes, extent_cache, chunk_cache,
+                                    dev_cache, block_group_cache,
+                                    dev_extent_cache, NULL);
+               if (ret != 0) {
+                       if (ret > 0)
+                               ret = 0;
+                       break;
+               }
        }
-
-       btrfs_free_path(path);
-
-       if (!ret && !nr_del)
-               rec->num_duplicates = 0;
-
-       return ret ? ret : nr_del;
+       return ret;
 }
 
-static int find_possible_backrefs(struct btrfs_fs_info *info,
-                                 struct btrfs_path *path,
-                                 struct cache_tree *extent_cache,
-                                 struct extent_record *rec)
+static int check_chunks_and_extents(struct btrfs_root *root)
 {
-       struct btrfs_root *root;
-       struct extent_backref *back;
-       struct data_backref *dback;
-       struct cache_extent *cache;
-       struct btrfs_file_extent_item *fi;
+       struct rb_root dev_cache;
+       struct cache_tree chunk_cache;
+       struct block_group_tree block_group_cache;
+       struct device_extent_tree dev_extent_cache;
+       struct cache_tree extent_cache;
+       struct cache_tree seen;
+       struct cache_tree pending;
+       struct cache_tree reada;
+       struct cache_tree nodes;
+       struct extent_io_tree excluded_extents;
+       struct cache_tree corrupt_blocks;
+       struct btrfs_path path;
        struct btrfs_key key;
-       u64 bytenr, bytes;
-       int ret;
-
-       list_for_each_entry(back, &rec->backrefs, list) {
-               /* Don't care about full backrefs (poor unloved backrefs) */
-               if (back->full_backref || !back->is_data)
-                       continue;
-
-               dback = (struct data_backref *)back;
-
-               /* We found this one, we don't need to do a lookup */
-               if (dback->found_ref)
-                       continue;
+       struct btrfs_key found_key;
+       int ret, err = 0;
+       struct block_info *bits;
+       int bits_nr;
+       struct extent_buffer *leaf;
+       int slot;
+       struct btrfs_root_item ri;
+       struct list_head dropping_trees;
+       struct list_head normal_trees;
+       struct btrfs_root *root1;
+       u64 objectid;
+       u32 level_size;
+       u8 level;
 
-               key.objectid = dback->root;
-               key.type = BTRFS_ROOT_ITEM_KEY;
-               key.offset = (u64)-1;
+       dev_cache = RB_ROOT;
+       cache_tree_init(&chunk_cache);
+       block_group_tree_init(&block_group_cache);
+       device_extent_tree_init(&dev_extent_cache);
 
-               root = btrfs_read_fs_root(info, &key);
+       cache_tree_init(&extent_cache);
+       cache_tree_init(&seen);
+       cache_tree_init(&pending);
+       cache_tree_init(&nodes);
+       cache_tree_init(&reada);
+       cache_tree_init(&corrupt_blocks);
+       extent_io_tree_init(&excluded_extents);
+       INIT_LIST_HEAD(&dropping_trees);
+       INIT_LIST_HEAD(&normal_trees);
 
-               /* No root, definitely a bad ref, skip */
-               if (IS_ERR(root) && PTR_ERR(root) == -ENOENT)
-                       continue;
-               /* Other err, exit */
-               if (IS_ERR(root))
-                       return PTR_ERR(root);
+       if (repair) {
+               root->fs_info->excluded_extents = &excluded_extents;
+               root->fs_info->fsck_extent_cache = &extent_cache;
+               root->fs_info->free_extent_hook = free_extent_hook;
+               root->fs_info->corrupt_blocks = &corrupt_blocks;
+       }
 
-               key.objectid = dback->owner;
-               key.type = BTRFS_EXTENT_DATA_KEY;
-               key.offset = dback->offset;
-               ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-               if (ret) {
-                       btrfs_release_path(path);
-                       if (ret < 0)
-                               return ret;
-                       /* Didn't find it, we can carry on */
-                       ret = 0;
-                       continue;
-               }
+       bits_nr = 1024;
+       bits = malloc(bits_nr * sizeof(struct block_info));
+       if (!bits) {
+               perror("malloc");
+               exit(1);
+       }
 
-               fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
-                                   struct btrfs_file_extent_item);
-               bytenr = btrfs_file_extent_disk_bytenr(path->nodes[0], fi);
-               bytes = btrfs_file_extent_disk_num_bytes(path->nodes[0], fi);
-               btrfs_release_path(path);
-               cache = lookup_cache_extent(extent_cache, bytenr, 1);
-               if (cache) {
-                       struct extent_record *tmp;
-                       tmp = container_of(cache, struct extent_record, cache);
+       if (ctx.progress_enabled) {
+               ctx.tp = TASK_EXTENTS;
+               task_start(ctx.info);
+       }
 
-                       /*
-                        * If we found an extent record for the bytenr for this
-                        * particular backref then we can't add it to our
-                        * current extent record.  We only want to add backrefs
-                        * that don't have a corresponding extent item in the
-                        * extent tree since they likely belong to this record
-                        * and we need to fix it if it doesn't match bytenrs.
-                        */
-                       if  (tmp->found_rec)
-                               continue;
+again:
+       root1 = root->fs_info->tree_root;
+       level = btrfs_header_level(root1->node);
+       ret = add_root_item_to_list(&normal_trees, root1->root_key.objectid,
+                                   root1->node->start, 0, level, 0,
+                                   root1->nodesize, NULL);
+       if (ret < 0)
+               goto out;
+       root1 = root->fs_info->chunk_root;
+       level = btrfs_header_level(root1->node);
+       ret = add_root_item_to_list(&normal_trees, root1->root_key.objectid,
+                                   root1->node->start, 0, level, 0,
+                                   root1->nodesize, NULL);
+       if (ret < 0)
+               goto out;
+       btrfs_init_path(&path);
+       key.offset = 0;
+       key.objectid = 0;
+       key.type = BTRFS_ROOT_ITEM_KEY;
+       ret = btrfs_search_slot(NULL, root->fs_info->tree_root,
+                                       &key, &path, 0, 0);
+       if (ret < 0)
+               goto out;
+       while(1) {
+               leaf = path.nodes[0];
+               slot = path.slots[0];
+               if (slot >= btrfs_header_nritems(path.nodes[0])) {
+                       ret = btrfs_next_leaf(root, &path);
+                       if (ret != 0)
+                               break;
+                       leaf = path.nodes[0];
+                       slot = path.slots[0];
                }
+               btrfs_item_key_to_cpu(leaf, &found_key, path.slots[0]);
+               if (found_key.type == BTRFS_ROOT_ITEM_KEY) {
+                       unsigned long offset;
+                       u64 last_snapshot;
 
-               dback->found_ref += 1;
-               dback->disk_bytenr = bytenr;
-               dback->bytes = bytes;
-
-               /*
-                * Set this so the verify backref code knows not to trust the
-                * values in this backref.
-                */
-               back->broken = 1;
+                       offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
+                       read_extent_buffer(leaf, &ri, offset, sizeof(ri));
+                       last_snapshot = btrfs_root_last_snapshot(&ri);
+                       if (btrfs_disk_key_objectid(&ri.drop_progress) == 0) {
+                               level = btrfs_root_level(&ri);
+                               level_size = root->nodesize;
+                               ret = add_root_item_to_list(&normal_trees,
+                                               found_key.objectid,
+                                               btrfs_root_bytenr(&ri),
+                                               last_snapshot, level,
+                                               0, level_size, NULL);
+                               if (ret < 0)
+                                       goto out;
+                       } else {
+                               level = btrfs_root_level(&ri);
+                               level_size = root->nodesize;
+                               objectid = found_key.objectid;
+                               btrfs_disk_key_to_cpu(&found_key,
+                                                     &ri.drop_progress);
+                               ret = add_root_item_to_list(&dropping_trees,
+                                               objectid,
+                                               btrfs_root_bytenr(&ri),
+                                               last_snapshot, level,
+                                               ri.drop_level,
+                                               level_size, &found_key);
+                               if (ret < 0)
+                                       goto out;
+                       }
+               }
+               path.slots[0]++;
        }
+       btrfs_release_path(&path);
 
-       return 0;
-}
-
-/*
- * Record orphan data ref into corresponding root.
- *
- * Return 0 if the extent item contains data ref and recorded.
- * Return 1 if the extent item contains no useful data ref
- *   On that case, it may contains only shared_dataref or metadata backref
- *   or the file extent exists(this should be handled by the extent bytenr
- *   recovery routine)
- * Return <0 if something goes wrong.
- */
-static int record_orphan_data_extents(struct btrfs_fs_info *fs_info,
-                                     struct extent_record *rec)
-{
-       struct btrfs_key key;
-       struct btrfs_root *dest_root;
-       struct extent_backref *back;
-       struct data_backref *dback;
-       struct orphan_data_extent *orphan;
-       struct btrfs_path *path;
-       int recorded_data_ref = 0;
-       int ret = 0;
-
-       if (rec->metadata)
-               return 1;
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-       list_for_each_entry(back, &rec->backrefs, list) {
-               if (back->full_backref || !back->is_data ||
-                   !back->found_extent_tree)
-                       continue;
-               dback = (struct data_backref *)back;
-               if (dback->found_ref)
-                       continue;
-               key.objectid = dback->root;
-               key.type = BTRFS_ROOT_ITEM_KEY;
-               key.offset = (u64)-1;
+       /*
+        * check_block can return -EAGAIN if it fixes something, please keep
+        * this in mind when dealing with return values from these functions, if
+        * we get -EAGAIN we want to fall through and restart the loop.
+        */
+       ret = deal_root_from_list(&normal_trees, root, bits, bits_nr, &pending,
+                                 &seen, &reada, &nodes, &extent_cache,
+                                 &chunk_cache, &dev_cache, &block_group_cache,
+                                 &dev_extent_cache);
+       if (ret < 0) {
+               if (ret == -EAGAIN)
+                       goto loop;
+               goto out;
+       }
+       ret = deal_root_from_list(&dropping_trees, root, bits, bits_nr,
+                                 &pending, &seen, &reada, &nodes,
+                                 &extent_cache, &chunk_cache, &dev_cache,
+                                 &block_group_cache, &dev_extent_cache);
+       if (ret < 0) {
+               if (ret == -EAGAIN)
+                       goto loop;
+               goto out;
+       }
 
-               dest_root = btrfs_read_fs_root(fs_info, &key);
+       ret = check_chunks(&chunk_cache, &block_group_cache,
+                          &dev_extent_cache, NULL, NULL, NULL, 0);
+       if (ret) {
+               if (ret == -EAGAIN)
+                       goto loop;
+               err = ret;
+       }
 
-               /* For non-exist root we just skip it */
-               if (IS_ERR(dest_root) || !dest_root)
-                       continue;
+       ret = check_extent_refs(root, &extent_cache);
+       if (ret < 0) {
+               if (ret == -EAGAIN)
+                       goto loop;
+               goto out;
+       }
 
-               key.objectid = dback->owner;
-               key.type = BTRFS_EXTENT_DATA_KEY;
-               key.offset = dback->offset;
+       ret = check_devices(&dev_cache, &dev_extent_cache);
+       if (ret && err)
+               ret = err;
 
-               ret = btrfs_search_slot(NULL, dest_root, &key, path, 0, 0);
-               /*
-                * For ret < 0, it's OK since the fs-tree may be corrupted,
-                * we need to record it for inode/file extent rebuild.
-                * For ret > 0, we record it only for file extent rebuild.
-                * For ret == 0, the file extent exists but only bytenr
-                * mismatch, let the original bytenr fix routine to handle,
-                * don't record it.
-                */
-               if (ret == 0)
-                       continue;
-               ret = 0;
-               orphan = malloc(sizeof(*orphan));
-               if (!orphan) {
-                       ret = -ENOMEM;
-                       goto out;
-               }
-               INIT_LIST_HEAD(&orphan->list);
-               orphan->root = dback->root;
-               orphan->objectid = dback->owner;
-               orphan->offset = dback->offset;
-               orphan->disk_bytenr = rec->cache.start;
-               orphan->disk_len = rec->cache.size;
-               list_add(&dest_root->orphan_data_extents, &orphan->list);
-               recorded_data_ref = 1;
-       }
 out:
-       btrfs_free_path(path);
-       if (!ret)
-               return !recorded_data_ref;
-       else
-               return ret;
+       task_stop(ctx.info);
+       if (repair) {
+               free_corrupt_blocks_tree(root->fs_info->corrupt_blocks);
+               extent_io_tree_cleanup(&excluded_extents);
+               root->fs_info->fsck_extent_cache = NULL;
+               root->fs_info->free_extent_hook = NULL;
+               root->fs_info->corrupt_blocks = NULL;
+               root->fs_info->excluded_extents = NULL;
+       }
+       free(bits);
+       free_chunk_cache_tree(&chunk_cache);
+       free_device_cache_tree(&dev_cache);
+       free_block_group_tree(&block_group_cache);
+       free_device_extent_tree(&dev_extent_cache);
+       free_extent_cache_tree(&seen);
+       free_extent_cache_tree(&pending);
+       free_extent_cache_tree(&reada);
+       free_extent_cache_tree(&nodes);
+       return ret;
+loop:
+       free_corrupt_blocks_tree(root->fs_info->corrupt_blocks);
+       free_extent_cache_tree(&seen);
+       free_extent_cache_tree(&pending);
+       free_extent_cache_tree(&reada);
+       free_extent_cache_tree(&nodes);
+       free_chunk_cache_tree(&chunk_cache);
+       free_block_group_tree(&block_group_cache);
+       free_device_cache_tree(&dev_cache);
+       free_device_extent_tree(&dev_extent_cache);
+       free_extent_record_cache(root->fs_info, &extent_cache);
+       free_root_item_list(&normal_trees);
+       free_root_item_list(&dropping_trees);
+       extent_io_tree_cleanup(&excluded_extents);
+       goto again;
 }
 
 /*
- * when an incorrect extent item is found, this will delete
- * all of the existing entries for it and recreate them
- * based on what the tree scan found.
+ * Check backrefs of a tree block given by @bytenr or @eb.
+ *
+ * @root:      the root containing the @bytenr or @eb
+ * @eb:                tree block extent buffer, can be NULL
+ * @bytenr:    bytenr of the tree block to search
+ * @level:     tree level of the tree block
+ * @owner:     owner of the tree block
+ *
+ * Return >0 for any error found and output error message
+ * Return 0 for no error found
  */
-static int fixup_extent_refs(struct btrfs_fs_info *info,
-                            struct cache_tree *extent_cache,
-                            struct extent_record *rec)
+static int check_tree_block_ref(struct btrfs_root *root,
+                               struct extent_buffer *eb, u64 bytenr,
+                               int level, u64 owner)
 {
-       struct btrfs_trans_handle *trans = NULL;
+       struct btrfs_key key;
+       struct btrfs_root *extent_root = root->fs_info->extent_root;
+       struct btrfs_path path;
+       struct btrfs_extent_item *ei;
+       struct btrfs_extent_inline_ref *iref;
+       struct extent_buffer *leaf;
+       unsigned long end;
+       unsigned long ptr;
+       int slot;
+       int skinny_level;
+       int type;
+       u32 nodesize = root->nodesize;
+       u32 item_size;
+       u64 offset;
+       int found_ref = 0;
+       int err = 0;
        int ret;
-       struct btrfs_path *path;
-       struct list_head *cur = rec->backrefs.next;
-       struct cache_extent *cache;
-       struct extent_backref *back;
-       int allocated = 0;
-       u64 flags = 0;
-
-       if (rec->flag_block_full_backref)
-               flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
-       if (rec->refs != rec->extent_item_refs && !rec->metadata) {
-               /*
-                * Sometimes the backrefs themselves are so broken they don't
-                * get attached to any meaningful rec, so first go back and
-                * check any of our backrefs that we couldn't find and throw
-                * them into the list if we find the backref so that
-                * verify_backrefs can figure out what to do.
-                */
-               ret = find_possible_backrefs(info, path, extent_cache, rec);
-               if (ret < 0)
-                       goto out;
-       }
+       btrfs_init_path(&path);
+       key.objectid = bytenr;
+       if (btrfs_fs_incompat(root->fs_info,
+                             BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA))
+               key.type = BTRFS_METADATA_ITEM_KEY;
+       else
+               key.type = BTRFS_EXTENT_ITEM_KEY;
+       key.offset = (u64)-1;
 
-       /* step one, make sure all of the backrefs agree */
-       ret = verify_backrefs(info, path, rec);
-       if (ret < 0)
+       /* Search for the backref in extent tree */
+       ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
+       if (ret < 0) {
+               err |= BACKREF_MISSING;
                goto out;
-
-       trans = btrfs_start_transaction(info->extent_root, 1);
-       if (IS_ERR(trans)) {
-               ret = PTR_ERR(trans);
+       }
+       ret = btrfs_previous_extent_item(extent_root, &path, bytenr);
+       if (ret) {
+               err |= BACKREF_MISSING;
                goto out;
        }
 
-       /* step two, delete all the existing records */
-       ret = delete_extent_records(trans, info->extent_root, path,
-                                   rec->start, rec->max_size);
+       leaf = path.nodes[0];
+       slot = path.slots[0];
+       btrfs_item_key_to_cpu(leaf, &key, slot);
+
+       ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 
-       if (ret < 0)
-               goto out;
+       if (key.type == BTRFS_METADATA_ITEM_KEY) {
+               skinny_level = (int)key.offset;
+               iref = (struct btrfs_extent_inline_ref *)(ei + 1);
+       } else {
+               struct btrfs_tree_block_info *info;
 
-       /* was this block corrupt?  If so, don't add references to it */
-       cache = lookup_cache_extent(info->corrupt_blocks,
-                                   rec->start, rec->max_size);
-       if (cache) {
-               ret = 0;
-               goto out;
+               info = (struct btrfs_tree_block_info *)(ei + 1);
+               skinny_level = btrfs_tree_block_level(leaf, info);
+               iref = (struct btrfs_extent_inline_ref *)(info + 1);
        }
 
-       /* step three, recreate all the refs we did find */
-       while(cur != &rec->backrefs) {
-               back = list_entry(cur, struct extent_backref, list);
-               cur = cur->next;
+       if (eb) {
+               u64 header_gen;
+               u64 extent_gen;
 
-               /*
-                * if we didn't find any references, don't create a
-                * new extent record
-                */
-               if (!back->found_ref)
-                       continue;
+               if (!(btrfs_extent_flags(leaf, ei) &
+                     BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
+                       error(
+               "extent[%llu %u] backref type mismatch, missing bit: %llx",
+                               key.objectid, nodesize,
+                               BTRFS_EXTENT_FLAG_TREE_BLOCK);
+                       err = BACKREF_MISMATCH;
+               }
+               header_gen = btrfs_header_generation(eb);
+               extent_gen = btrfs_extent_generation(leaf, ei);
+               if (header_gen != extent_gen) {
+                       error(
+       "extent[%llu %u] backref generation mismatch, wanted: %llu, have: %llu",
+                               key.objectid, nodesize, header_gen,
+                               extent_gen);
+                       err = BACKREF_MISMATCH;
+               }
+               if (level != skinny_level) {
+                       error(
+                       "extent[%llu %u] level mismatch, wanted: %u, have: %u",
+                               key.objectid, nodesize, level, skinny_level);
+                       err = BACKREF_MISMATCH;
+               }
+               if (!is_fstree(owner) && btrfs_extent_refs(leaf, ei) != 1) {
+                       error(
+                       "extent[%llu %u] is referred by other roots than %llu",
+                               key.objectid, nodesize, root->objectid);
+                       err = BACKREF_MISMATCH;
+               }
+       }
 
-               rec->bad_full_backref = 0;
-               ret = record_extent(trans, info, path, rec, back, allocated, flags);
-               allocated = 1;
+       /*
+        * Iterate the extent/metadata item to find the exact backref
+        */
+       item_size = btrfs_item_size_nr(leaf, slot);
+       ptr = (unsigned long)iref;
+       end = (unsigned long)ei + item_size;
+       while (ptr < end) {
+               iref = (struct btrfs_extent_inline_ref *)ptr;
+               type = btrfs_extent_inline_ref_type(leaf, iref);
+               offset = btrfs_extent_inline_ref_offset(leaf, iref);
 
-               if (ret)
-                       goto out;
+               if (type == BTRFS_TREE_BLOCK_REF_KEY &&
+                       (offset == root->objectid || offset == owner)) {
+                       found_ref = 1;
+               } else if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
+                       /* Check if the backref points to valid referencer */
+                       found_ref = !check_tree_block_ref(root, NULL, offset,
+                                                         level + 1, owner);
+               }
+
+               if (found_ref)
+                       break;
+               ptr += btrfs_extent_inline_ref_size(type);
        }
-out:
-       if (trans) {
-               int err = btrfs_commit_transaction(trans, info->extent_root);
+
+       /*
+        * Inlined extent item doesn't have what we need, check
+        * TREE_BLOCK_REF_KEY
+        */
+       if (!found_ref) {
+               btrfs_release_path(&path);
+               key.objectid = bytenr;
+               key.type = BTRFS_TREE_BLOCK_REF_KEY;
+               key.offset = root->objectid;
+
+               ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
                if (!ret)
-                       ret = err;
+                       found_ref = 1;
        }
-
-       btrfs_free_path(path);
-       return ret;
+       if (!found_ref)
+               err |= BACKREF_MISSING;
+out:
+       btrfs_release_path(&path);
+       if (eb && (err & BACKREF_MISSING))
+               error("extent[%llu %u] backref lost (owner: %llu, level: %u)",
+                       bytenr, nodesize, owner, level);
+       return err;
 }
 
-static int fixup_extent_flags(struct btrfs_fs_info *fs_info,
-                             struct extent_record *rec)
+/*
+ * Check EXTENT_DATA item, mainly for its dbackref in extent tree
+ *
+ * Return >0 any error found and output error message
+ * Return 0 for no error found
+ */
+static int check_extent_data_item(struct btrfs_root *root,
+                                 struct extent_buffer *eb, int slot)
 {
-       struct btrfs_trans_handle *trans;
-       struct btrfs_root *root = fs_info->extent_root;
-       struct btrfs_path *path;
+       struct btrfs_file_extent_item *fi;
+       struct btrfs_path path;
+       struct btrfs_root *extent_root = root->fs_info->extent_root;
+       struct btrfs_key fi_key;
+       struct btrfs_key dbref_key;
+       struct extent_buffer *leaf;
        struct btrfs_extent_item *ei;
-       struct btrfs_key key;
-       u64 flags;
-       int ret = 0;
+       struct btrfs_extent_inline_ref *iref;
+       struct btrfs_extent_data_ref *dref;
+       u64 owner;
+       u64 file_extent_gen;
+       u64 disk_bytenr;
+       u64 disk_num_bytes;
+       u64 extent_num_bytes;
+       u64 extent_flags;
+       u64 extent_gen;
+       u32 item_size;
+       unsigned long end;
+       unsigned long ptr;
+       int type;
+       u64 ref_root;
+       int found_dbackref = 0;
+       int err = 0;
+       int ret;
 
-       key.objectid = rec->start;
-       if (rec->metadata) {
-               key.type = BTRFS_METADATA_ITEM_KEY;
-               key.offset = rec->info_level;
+       btrfs_item_key_to_cpu(eb, &fi_key, slot);
+       fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+       file_extent_gen = btrfs_file_extent_generation(eb, fi);
+
+       /* Nothing to check for hole and inline data extents */
+       if (btrfs_file_extent_type(eb, fi) == BTRFS_FILE_EXTENT_INLINE ||
+           btrfs_file_extent_disk_bytenr(eb, fi) == 0)
+               return 0;
+
+       disk_bytenr = btrfs_file_extent_disk_bytenr(eb, fi);
+       disk_num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);
+       extent_num_bytes = btrfs_file_extent_num_bytes(eb, fi);
+
+       /* Check unaligned disk_num_bytes and num_bytes */
+       if (!IS_ALIGNED(disk_num_bytes, root->sectorsize)) {
+               error(
+"file extent [%llu, %llu] has unaligned disk num bytes: %llu, should be aligned to %u",
+                       fi_key.objectid, fi_key.offset, disk_num_bytes,
+                       root->sectorsize);
+               err |= BYTES_UNALIGNED;
        } else {
-               key.type = BTRFS_EXTENT_ITEM_KEY;
-               key.offset = rec->max_size;
+               data_bytes_allocated += disk_num_bytes;
+       }
+       if (!IS_ALIGNED(extent_num_bytes, root->sectorsize)) {
+               error(
+"file extent [%llu, %llu] has unaligned num bytes: %llu, should be aligned to %u",
+                       fi_key.objectid, fi_key.offset, extent_num_bytes,
+                       root->sectorsize);
+               err |= BYTES_UNALIGNED;
+       } else {
+               data_bytes_referenced += extent_num_bytes;
        }
+       owner = btrfs_header_owner(eb);
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
+       /* Check the extent item of the file extent in extent tree */
+       btrfs_init_path(&path);
+       dbref_key.objectid = btrfs_file_extent_disk_bytenr(eb, fi);
+       dbref_key.type = BTRFS_EXTENT_ITEM_KEY;
+       dbref_key.offset = btrfs_file_extent_disk_num_bytes(eb, fi);
 
-       trans = btrfs_start_transaction(root, 0);
-       if (IS_ERR(trans)) {
-               btrfs_free_path(path);
-               return PTR_ERR(trans);
+       ret = btrfs_search_slot(NULL, extent_root, &dbref_key, &path, 0, 0);
+       if (ret) {
+               err |= BACKREF_MISSING;
+               goto error;
        }
 
-       ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
-       if (ret < 0) {
-               btrfs_free_path(path);
-               btrfs_commit_transaction(trans, root);
-               return ret;
-       } else if (ret) {
-               fprintf(stderr, "Didn't find extent for %llu\n",
-                       (unsigned long long)rec->start);
-               btrfs_free_path(path);
-               btrfs_commit_transaction(trans, root);
-               return -ENOENT;
+       leaf = path.nodes[0];
+       slot = path.slots[0];
+       ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
+
+       extent_flags = btrfs_extent_flags(leaf, ei);
+       extent_gen = btrfs_extent_generation(leaf, ei);
+
+       if (!(extent_flags & BTRFS_EXTENT_FLAG_DATA)) {
+               error(
+                   "extent[%llu %llu] backref type mismatch, wanted bit: %llx",
+                   disk_bytenr, disk_num_bytes,
+                   BTRFS_EXTENT_FLAG_DATA);
+               err |= BACKREF_MISMATCH;
        }
 
-       ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
-                           struct btrfs_extent_item);
-       flags = btrfs_extent_flags(path->nodes[0], ei);
-       if (rec->flag_block_full_backref) {
-               fprintf(stderr, "setting full backref on %llu\n",
-                       (unsigned long long)key.objectid);
-               flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
-       } else {
-               fprintf(stderr, "clearing full backref on %llu\n",
-                       (unsigned long long)key.objectid);
-               flags &= ~BTRFS_BLOCK_FLAG_FULL_BACKREF;
+       if (file_extent_gen < extent_gen) {
+               error(
+"extent[%llu %llu] backref generation mismatch, wanted: <=%llu, have: %llu",
+                       disk_bytenr, disk_num_bytes, file_extent_gen,
+                       extent_gen);
+               err |= BACKREF_MISMATCH;
        }
-       btrfs_set_extent_flags(path->nodes[0], ei, flags);
-       btrfs_mark_buffer_dirty(path->nodes[0]);
-       btrfs_free_path(path);
-       return btrfs_commit_transaction(trans, root);
+
+       /* Check data backref inside that extent item */
+       item_size = btrfs_item_size_nr(leaf, path.slots[0]);
+       iref = (struct btrfs_extent_inline_ref *)(ei + 1);
+       ptr = (unsigned long)iref;
+       end = (unsigned long)ei + item_size;
+       while (ptr < end) {
+               iref = (struct btrfs_extent_inline_ref *)ptr;
+               type = btrfs_extent_inline_ref_type(leaf, iref);
+               dref = (struct btrfs_extent_data_ref *)(&iref->offset);
+
+               if (type == BTRFS_EXTENT_DATA_REF_KEY) {
+                       ref_root = btrfs_extent_data_ref_root(leaf, dref);
+                       if (ref_root == owner || ref_root == root->objectid)
+                               found_dbackref = 1;
+               } else if (type == BTRFS_SHARED_DATA_REF_KEY) {
+                       found_dbackref = !check_tree_block_ref(root, NULL,
+                               btrfs_extent_inline_ref_offset(leaf, iref),
+                               0, owner);
+               }
+
+               if (found_dbackref)
+                       break;
+               ptr += btrfs_extent_inline_ref_size(type);
+       }
+
+       /* Didn't found inlined data backref, try EXTENT_DATA_REF_KEY */
+       if (!found_dbackref) {
+               btrfs_release_path(&path);
+
+               btrfs_init_path(&path);
+               dbref_key.objectid = btrfs_file_extent_disk_bytenr(eb, fi);
+               dbref_key.type = BTRFS_EXTENT_DATA_REF_KEY;
+               dbref_key.offset = hash_extent_data_ref(root->objectid,
+                               fi_key.objectid, fi_key.offset);
+
+               ret = btrfs_search_slot(NULL, root->fs_info->extent_root,
+                                       &dbref_key, &path, 0, 0);
+               if (!ret)
+                       found_dbackref = 1;
+       }
+
+       if (!found_dbackref)
+               err |= BACKREF_MISSING;
+error:
+       btrfs_release_path(&path);
+       if (err & BACKREF_MISSING) {
+               error("data extent[%llu %llu] backref lost",
+                     disk_bytenr, disk_num_bytes);
+       }
+       return err;
 }
 
-/* right now we only prune from the extent allocation tree */
-static int prune_one_block(struct btrfs_trans_handle *trans,
-                          struct btrfs_fs_info *info,
-                          struct btrfs_corrupt_block *corrupt)
+/*
+ * Get real tree block level for the case like shared block
+ * Return >= 0 as tree level
+ * Return <0 for error
+ */
+static int query_tree_block_level(struct btrfs_fs_info *fs_info, u64 bytenr)
 {
-       int ret;
-       struct btrfs_path path;
        struct extent_buffer *eb;
-       u64 found;
-       int slot;
-       int nritems;
-       int level = corrupt->level + 1;
-
-       btrfs_init_path(&path);
-again:
-       /* we want to stop at the parent to our busted block */
-       path.lowest_level = level;
+       struct btrfs_path path;
+       struct btrfs_key key;
+       struct btrfs_extent_item *ei;
+       u64 flags;
+       u64 transid;
+       u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       u8 backref_level;
+       u8 header_level;
+       int ret;
 
-       ret = btrfs_search_slot(trans, info->extent_root,
-                               &corrupt->key, &path, -1, 1);
+       /* Search extent tree for extent generation and level */
+       key.objectid = bytenr;
+       key.type = BTRFS_METADATA_ITEM_KEY;
+       key.offset = (u64)-1;
 
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, &path, 0, 0);
        if (ret < 0)
-               goto out;
+               goto release_out;
+       ret = btrfs_previous_extent_item(fs_info->extent_root, &path, bytenr);
+       if (ret < 0)
+               goto release_out;
+       if (ret > 0) {
+               ret = -ENOENT;
+               goto release_out;
+       }
 
-       eb = path.nodes[level];
-       if (!eb) {
+       btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+       ei = btrfs_item_ptr(path.nodes[0], path.slots[0],
+                           struct btrfs_extent_item);
+       flags = btrfs_extent_flags(path.nodes[0], ei);
+       if (!(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
                ret = -ENOENT;
-               goto out;
+               goto release_out;
        }
 
-       /*
-        * hopefully the search gave us the block we want to prune,
-        * lets try that first
-        */
-       slot = path.slots[level];
-       found =  btrfs_node_blockptr(eb, slot);
-       if (found == corrupt->cache.start)
-               goto del_ptr;
+       /* Get transid for later read_tree_block() check */
+       transid = btrfs_extent_generation(path.nodes[0], ei);
 
-       nritems = btrfs_header_nritems(eb);
+       /* Get backref level as one source */
+       if (key.type == BTRFS_METADATA_ITEM_KEY) {
+               backref_level = key.offset;
+       } else {
+               struct btrfs_tree_block_info *info;
 
-       /* the search failed, lets scan this node and hope we find it */
-       for (slot = 0; slot < nritems; slot++) {
-               found =  btrfs_node_blockptr(eb, slot);
-               if (found == corrupt->cache.start)
-                       goto del_ptr;
+               info = (struct btrfs_tree_block_info *)(ei + 1);
+               backref_level = btrfs_tree_block_level(path.nodes[0], info);
        }
-       /*
-        * we couldn't find the bad block.  TODO, search all the nodes for pointers
-        * to this block
-        */
-       if (eb == info->extent_root->node) {
-               ret = -ENOENT;
-               goto out;
-       } else {
-               level++;
-               btrfs_release_path(&path);
-               goto again;
+       btrfs_release_path(&path);
+
+       /* Get level from tree block as an alternative source */
+       eb = read_tree_block_fs_info(fs_info, bytenr, nodesize, transid);
+       if (!extent_buffer_uptodate(eb)) {
+               free_extent_buffer(eb);
+               return -EIO;
        }
+       header_level = btrfs_header_level(eb);
+       free_extent_buffer(eb);
 
-del_ptr:
-       printk("deleting pointer to block %Lu\n", corrupt->cache.start);
-       ret = btrfs_del_ptr(trans, info->extent_root, &path, level, slot);
+       if (header_level != backref_level)
+               return -EIO;
+       return header_level;
 
-out:
+release_out:
        btrfs_release_path(&path);
        return ret;
 }
 
-static int prune_corrupt_blocks(struct btrfs_fs_info *info)
+/*
+ * Check if a tree block backref is valid (points to a valid tree block)
+ * if level == -1, level will be resolved
+ * Return >0 for any error found and print error message
+ */
+static int check_tree_block_backref(struct btrfs_fs_info *fs_info, u64 root_id,
+                                   u64 bytenr, int level)
 {
-       struct btrfs_trans_handle *trans = NULL;
-       struct cache_extent *cache;
-       struct btrfs_corrupt_block *corrupt;
+       struct btrfs_root *root;
+       struct btrfs_key key;
+       struct btrfs_path path;
+       struct extent_buffer *eb;
+       struct extent_buffer *node;
+       u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       int err = 0;
+       int ret;
 
-       while (1) {
-               cache = search_cache_extent(info->corrupt_blocks, 0);
-               if (!cache)
-                       break;
-               if (!trans) {
-                       trans = btrfs_start_transaction(info->extent_root, 1);
-                       if (IS_ERR(trans))
-                               return PTR_ERR(trans);
-               }
-               corrupt = container_of(cache, struct btrfs_corrupt_block, cache);
-               prune_one_block(trans, info, corrupt);
-               remove_cache_extent(info->corrupt_blocks, cache);
+       /* Query level for level == -1 special case */
+       if (level == -1)
+               level = query_tree_block_level(fs_info, bytenr);
+       if (level < 0) {
+               err |= REFERENCER_MISSING;
+               goto out;
+       }
+
+       key.objectid = root_id;
+       key.type = BTRFS_ROOT_ITEM_KEY;
+       key.offset = (u64)-1;
+
+       root = btrfs_read_fs_root(fs_info, &key);
+       if (IS_ERR(root)) {
+               err |= REFERENCER_MISSING;
+               goto out;
+       }
+
+       /* Read out the tree block to get item/node key */
+       eb = read_tree_block(root, bytenr, root->nodesize, 0);
+       if (!extent_buffer_uptodate(eb)) {
+               err |= REFERENCER_MISSING;
+               free_extent_buffer(eb);
+               goto out;
+       }
+
+       /* Empty tree, no need to check key */
+       if (!btrfs_header_nritems(eb) && !level) {
+               free_extent_buffer(eb);
+               goto out;
        }
-       if (trans)
-               return btrfs_commit_transaction(trans, info->extent_root);
-       return 0;
-}
 
-static void reset_cached_block_groups(struct btrfs_fs_info *fs_info)
-{
-       struct btrfs_block_group_cache *cache;
-       u64 start, end;
-       int ret;
+       if (level)
+               btrfs_node_key_to_cpu(eb, &key, 0);
+       else
+               btrfs_item_key_to_cpu(eb, &key, 0);
 
-       while (1) {
-               ret = find_first_extent_bit(&fs_info->free_space_cache, 0,
-                                           &start, &end, EXTENT_DIRTY);
-               if (ret)
-                       break;
-               clear_extent_dirty(&fs_info->free_space_cache, start, end,
-                                  GFP_NOFS);
+       free_extent_buffer(eb);
+
+       btrfs_init_path(&path);
+       path.lowest_level = level;
+       /* Search with the first key, to ensure we can reach it */
+       ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+       if (ret < 0) {
+               err |= REFERENCER_MISSING;
+               goto release_out;
        }
 
-       start = 0;
-       while (1) {
-               cache = btrfs_lookup_first_block_group(fs_info, start);
-               if (!cache)
-                       break;
-               if (cache->cached)
-                       cache->cached = 0;
-               start = cache->key.objectid + cache->key.offset;
+       node = path.nodes[level];
+       if (btrfs_header_bytenr(node) != bytenr) {
+               error(
+       "extent [%llu %d] referencer bytenr mismatch, wanted: %llu, have: %llu",
+                       bytenr, nodesize, bytenr,
+                       btrfs_header_bytenr(node));
+               err |= REFERENCER_MISMATCH;
+       }
+       if (btrfs_header_level(node) != level) {
+               error(
+       "extent [%llu %d] referencer level mismatch, wanted: %d, have: %d",
+                       bytenr, nodesize, level,
+                       btrfs_header_level(node));
+               err |= REFERENCER_MISMATCH;
+       }
+
+release_out:
+       btrfs_release_path(&path);
+out:
+       if (err & REFERENCER_MISSING) {
+               if (level < 0)
+                       error("extent [%llu %d] lost referencer (owner: %llu)",
+                               bytenr, nodesize, root_id);
+               else
+                       error(
+               "extent [%llu %d] lost referencer (owner: %llu, level: %u)",
+                               bytenr, nodesize, root_id, level);
        }
+
+       return err;
 }
 
-static int check_extent_refs(struct btrfs_root *root,
-                            struct cache_tree *extent_cache)
+/*
+ * Check referencer for shared block backref
+ * If level == -1, this function will resolve the level.
+ */
+static int check_shared_block_backref(struct btrfs_fs_info *fs_info,
+                                    u64 parent, u64 bytenr, int level)
 {
-       struct extent_record *rec;
-       struct cache_extent *cache;
-       int err = 0;
-       int ret = 0;
-       int fixed = 0;
-       int had_dups = 0;
-       int recorded = 0;
+       struct extent_buffer *eb;
+       u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       u32 nr;
+       int found_parent = 0;
+       int i;
 
-       if (repair) {
-               /*
-                * if we're doing a repair, we have to make sure
-                * we don't allocate from the problem extents.
-                * In the worst case, this will be all the
-                * extents in the FS
-                */
-               cache = search_cache_extent(extent_cache, 0);
-               while(cache) {
-                       rec = container_of(cache, struct extent_record, cache);
-                       set_extent_dirty(root->fs_info->excluded_extents,
-                                        rec->start,
-                                        rec->start + rec->max_size - 1,
-                                        GFP_NOFS);
-                       cache = next_cache_extent(cache);
-               }
+       eb = read_tree_block_fs_info(fs_info, parent, nodesize, 0);
+       if (!extent_buffer_uptodate(eb))
+               goto out;
 
-               /* pin down all the corrupted blocks too */
-               cache = search_cache_extent(root->fs_info->corrupt_blocks, 0);
-               while(cache) {
-                       set_extent_dirty(root->fs_info->excluded_extents,
-                                        cache->start,
-                                        cache->start + cache->size - 1,
-                                        GFP_NOFS);
-                       cache = next_cache_extent(cache);
+       if (level == -1)
+               level = query_tree_block_level(fs_info, bytenr);
+       if (level < 0)
+               goto out;
+
+       if (level + 1 != btrfs_header_level(eb))
+               goto out;
+
+       nr = btrfs_header_nritems(eb);
+       for (i = 0; i < nr; i++) {
+               if (bytenr == btrfs_node_blockptr(eb, i)) {
+                       found_parent = 1;
+                       break;
                }
-               prune_corrupt_blocks(root->fs_info);
-               reset_cached_block_groups(root->fs_info);
        }
+out:
+       free_extent_buffer(eb);
+       if (!found_parent) {
+               error(
+       "shared extent[%llu %u] lost its parent (parent: %llu, level: %u)",
+                       bytenr, nodesize, parent, level);
+               return REFERENCER_MISSING;
+       }
+       return 0;
+}
 
-       reset_cached_block_groups(root->fs_info);
+/*
+ * Check referencer for normal (inlined) data ref
+ * If len == 0, it will be resolved by searching in extent tree
+ */
+static int check_extent_data_backref(struct btrfs_fs_info *fs_info,
+                                    u64 root_id, u64 objectid, u64 offset,
+                                    u64 bytenr, u64 len, u32 count)
+{
+       struct btrfs_root *root;
+       struct btrfs_root *extent_root = fs_info->extent_root;
+       struct btrfs_key key;
+       struct btrfs_path path;
+       struct extent_buffer *leaf;
+       struct btrfs_file_extent_item *fi;
+       u32 found_count = 0;
+       int slot;
+       int ret = 0;
 
-       /*
-        * We need to delete any duplicate entries we find first otherwise we
-        * could mess up the extent tree when we have backrefs that actually
-        * belong to a different extent item and not the weird duplicate one.
-        */
-       while (repair && !list_empty(&duplicate_extents)) {
-               rec = list_entry(duplicate_extents.next, struct extent_record,
-                                list);
-               list_del_init(&rec->list);
+       if (!len) {
+               key.objectid = bytenr;
+               key.type = BTRFS_EXTENT_ITEM_KEY;
+               key.offset = (u64)-1;
 
-               /* Sometimes we can find a backref before we find an actual
-                * extent, so we need to process it a little bit to see if there
-                * truly are multiple EXTENT_ITEM_KEY's for the same range, or
-                * if this is a backref screwup.  If we need to delete stuff
-                * process_duplicates() will return 0, otherwise it will return
-                * 1 and we
-                */
-               if (process_duplicates(root, extent_cache, rec))
-                       continue;
-               ret = delete_duplicate_records(root, rec);
+               btrfs_init_path(&path);
+               ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
                if (ret < 0)
-                       return ret;
-               /*
-                * delete_duplicate_records will return the number of entries
-                * deleted, so if it's greater than 0 then we know we actually
-                * did something and we need to remove.
-                */
+                       goto out;
+               ret = btrfs_previous_extent_item(extent_root, &path, bytenr);
                if (ret)
-                       had_dups = 1;
+                       goto out;
+               btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+               if (key.objectid != bytenr ||
+                   key.type != BTRFS_EXTENT_ITEM_KEY)
+                       goto out;
+               len = key.offset;
+               btrfs_release_path(&path);
        }
+       key.objectid = root_id;
+       key.type = BTRFS_ROOT_ITEM_KEY;
+       key.offset = (u64)-1;
+       btrfs_init_path(&path);
 
-       if (had_dups)
-               return -EAGAIN;
+       root = btrfs_read_fs_root(fs_info, &key);
+       if (IS_ERR(root))
+               goto out;
 
-       while(1) {
-               int cur_err = 0;
+       key.objectid = objectid;
+       key.type = BTRFS_EXTENT_DATA_KEY;
+       /*
+        * It can be nasty as data backref offset is
+        * file offset - file extent offset, which is smaller or
+        * equal to original backref offset.  The only special case is
+        * overflow.  So we need to special check and do further search.
+        */
+       key.offset = offset & (1ULL << 63) ? 0 : offset;
 
-               fixed = 0;
-               recorded = 0;
-               cache = search_cache_extent(extent_cache, 0);
-               if (!cache)
-                       break;
-               rec = container_of(cache, struct extent_record, cache);
-               if (rec->num_duplicates) {
-                       fprintf(stderr, "extent item %llu has multiple extent "
-                               "items\n", (unsigned long long)rec->start);
-                       err = 1;
-                       cur_err = 1;
-               }
+       ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+       if (ret < 0)
+               goto out;
 
-               if (rec->refs != rec->extent_item_refs) {
-                       fprintf(stderr, "ref mismatch on [%llu %llu] ",
-                               (unsigned long long)rec->start,
-                               (unsigned long long)rec->nr);
-                       fprintf(stderr, "extent item %llu, found %llu\n",
-                               (unsigned long long)rec->extent_item_refs,
-                               (unsigned long long)rec->refs);
-                       ret = record_orphan_data_extents(root->fs_info, rec);
-                       if (ret < 0)
-                               goto repair_abort;
-                       if (ret == 0) {
-                               recorded = 1;
-                       } else {
-                               /*
-                                * we can't use the extent to repair file
-                                * extent, let the fallback method handle it.
-                                */
-                               if (!fixed && repair) {
-                                       ret = fixup_extent_refs(
-                                                       root->fs_info,
-                                                       extent_cache, rec);
-                                       if (ret)
-                                               goto repair_abort;
-                                       fixed = 1;
-                               }
-                       }
-                       err = 1;
-                       cur_err = 1;
-               }
-               if (all_backpointers_checked(rec, 1)) {
-                       fprintf(stderr, "backpointer mismatch on [%llu %llu]\n",
-                               (unsigned long long)rec->start,
-                               (unsigned long long)rec->nr);
+       /*
+        * Search afterwards to get correct one
+        * NOTE: As we must do a comprehensive check on the data backref to
+        * make sure the dref count also matches, we must iterate all file
+        * extents for that inode.
+        */
+       while (1) {
+               leaf = path.nodes[0];
+               slot = path.slots[0];
 
-                       if (!fixed && !recorded && repair) {
-                               ret = fixup_extent_refs(root->fs_info,
-                                                       extent_cache, rec);
-                               if (ret)
-                                       goto repair_abort;
-                               fixed = 1;
-                       }
-                       cur_err = 1;
-                       err = 1;
-               }
-               if (!rec->owner_ref_checked) {
-                       fprintf(stderr, "owner ref check failed [%llu %llu]\n",
-                               (unsigned long long)rec->start,
-                               (unsigned long long)rec->nr);
-                       if (!fixed && !recorded && repair) {
-                               ret = fixup_extent_refs(root->fs_info,
-                                                       extent_cache, rec);
-                               if (ret)
-                                       goto repair_abort;
-                               fixed = 1;
-                       }
-                       err = 1;
-                       cur_err = 1;
-               }
-               if (rec->bad_full_backref) {
-                       fprintf(stderr, "bad full backref, on [%llu]\n",
-                               (unsigned long long)rec->start);
-                       if (repair) {
-                               ret = fixup_extent_flags(root->fs_info, rec);
-                               if (ret)
-                                       goto repair_abort;
-                               fixed = 1;
-                       }
-                       err = 1;
-                       cur_err = 1;
-               }
+               btrfs_item_key_to_cpu(leaf, &key, slot);
+               if (key.objectid != objectid || key.type != BTRFS_EXTENT_DATA_KEY)
+                       break;
+               fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
                /*
-                * Although it's not a extent ref's problem, we reuse this
-                * routine for error reporting.
-                * No repair function yet.
+                * Except normal disk bytenr and disk num bytes, we still
+                * need to do extra check on dbackref offset as
+                * dbackref offset = file_offset - file_extent_offset
                 */
-               if (rec->crossing_stripes) {
-                       fprintf(stderr,
-                               "bad metadata [%llu, %llu) crossing stripe boundary\n",
-                               rec->start, rec->start + rec->max_size);
-                       err = 1;
-                       cur_err = 1;
-               }
-
-               if (rec->wrong_chunk_type) {
-                       fprintf(stderr,
-                               "bad extent [%llu, %llu), type mismatch with chunk\n",
-                               rec->start, rec->start + rec->max_size);
-                       err = 1;
-                       cur_err = 1;
-               }
+               if (btrfs_file_extent_disk_bytenr(leaf, fi) == bytenr &&
+                   btrfs_file_extent_disk_num_bytes(leaf, fi) == len &&
+                   (u64)(key.offset - btrfs_file_extent_offset(leaf, fi)) ==
+                   offset)
+                       found_count++;
 
-               remove_cache_extent(extent_cache, cache);
-               free_all_extent_backrefs(rec);
-               if (!init_extent_tree && repair && (!cur_err || fixed))
-                       clear_extent_dirty(root->fs_info->excluded_extents,
-                                          rec->start,
-                                          rec->start + rec->max_size - 1,
-                                          GFP_NOFS);
-               free(rec);
+               ret = btrfs_next_item(root, &path);
+               if (ret)
+                       break;
        }
-repair_abort:
-       if (repair) {
-               if (ret && ret != -EAGAIN) {
-                       fprintf(stderr, "failed to repair damaged filesystem, aborting\n");
-                       exit(1);
-               } else if (!ret) {
-                       struct btrfs_trans_handle *trans;
+out:
+       btrfs_release_path(&path);
+       if (found_count != count) {
+               error(
+"extent[%llu, %llu] referencer count mismatch (root: %llu, owner: %llu, offset: %llu) wanted: %u, have: %u",
+                       bytenr, len, root_id, objectid, offset, count, found_count);
+               return REFERENCER_MISSING;
+       }
+       return 0;
+}
 
-                       root = root->fs_info->extent_root;
-                       trans = btrfs_start_transaction(root, 1);
-                       if (IS_ERR(trans)) {
-                               ret = PTR_ERR(trans);
-                               goto repair_abort;
-                       }
+/*
+ * Check if the referencer of a shared data backref exists
+ */
+static int check_shared_data_backref(struct btrfs_fs_info *fs_info,
+                                    u64 parent, u64 bytenr)
+{
+       struct extent_buffer *eb;
+       struct btrfs_key key;
+       struct btrfs_file_extent_item *fi;
+       u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       u32 nr;
+       int found_parent = 0;
+       int i;
 
-                       btrfs_fix_block_accounting(trans, root);
-                       ret = btrfs_commit_transaction(trans, root);
-                       if (ret)
-                               goto repair_abort;
+       eb = read_tree_block_fs_info(fs_info, parent, nodesize, 0);
+       if (!extent_buffer_uptodate(eb))
+               goto out;
+
+       nr = btrfs_header_nritems(eb);
+       for (i = 0; i < nr; i++) {
+               btrfs_item_key_to_cpu(eb, &key, i);
+               if (key.type != BTRFS_EXTENT_DATA_KEY)
+                       continue;
+
+               fi = btrfs_item_ptr(eb, i, struct btrfs_file_extent_item);
+               if (btrfs_file_extent_type(eb, fi) == BTRFS_FILE_EXTENT_INLINE)
+                       continue;
+
+               if (btrfs_file_extent_disk_bytenr(eb, fi) == bytenr) {
+                       found_parent = 1;
+                       break;
                }
-               if (err)
-                       fprintf(stderr, "repaired damaged extent references\n");
-               return ret;
        }
-       return err;
+
+out:
+       free_extent_buffer(eb);
+       if (!found_parent) {
+               error("shared extent %llu referencer lost (parent: %llu)",
+                       bytenr, parent);
+               return REFERENCER_MISSING;
+       }
+       return 0;
 }
 
-u64 calc_stripe_length(u64 type, u64 length, int num_stripes)
+/*
+ * This function will check a given extent item, including its backref and
+ * itself (like crossing stripe boundary and type)
+ *
+ * Since we don't use extent_record anymore, introduce new error bit
+ */
+static int check_extent_item(struct btrfs_fs_info *fs_info,
+                            struct extent_buffer *eb, int slot)
 {
-       u64 stripe_size;
+       struct btrfs_extent_item *ei;
+       struct btrfs_extent_inline_ref *iref;
+       struct btrfs_extent_data_ref *dref;
+       unsigned long end;
+       unsigned long ptr;
+       int type;
+       u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       u32 item_size = btrfs_item_size_nr(eb, slot);
+       u64 flags;
+       u64 offset;
+       int metadata = 0;
+       int level;
+       struct btrfs_key key;
+       int ret;
+       int err = 0;
 
-       if (type & BTRFS_BLOCK_GROUP_RAID0) {
-               stripe_size = length;
-               stripe_size /= num_stripes;
-       } else if (type & BTRFS_BLOCK_GROUP_RAID10) {
-               stripe_size = length * 2;
-               stripe_size /= num_stripes;
-       } else if (type & BTRFS_BLOCK_GROUP_RAID5) {
-               stripe_size = length;
-               stripe_size /= (num_stripes - 1);
-       } else if (type & BTRFS_BLOCK_GROUP_RAID6) {
-               stripe_size = length;
-               stripe_size /= (num_stripes - 2);
+       btrfs_item_key_to_cpu(eb, &key, slot);
+       if (key.type == BTRFS_EXTENT_ITEM_KEY)
+               bytes_used += key.offset;
+       else
+               bytes_used += nodesize;
+
+       if (item_size < sizeof(*ei)) {
+               /*
+                * COMPAT_EXTENT_TREE_V0 case, but it's already a super
+                * old thing when on disk format is still un-determined.
+                * No need to care about it anymore
+                */
+               error("unsupported COMPAT_EXTENT_TREE_V0 detected");
+               return -ENOTTY;
+       }
+
+       ei = btrfs_item_ptr(eb, slot, struct btrfs_extent_item);
+       flags = btrfs_extent_flags(eb, ei);
+
+       if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+               metadata = 1;
+       if (metadata && check_crossing_stripes(global_info, key.objectid,
+                                              eb->len)) {
+               error("bad metadata [%llu, %llu) crossing stripe boundary",
+                     key.objectid, key.objectid + nodesize);
+               err |= CROSSING_STRIPE_BOUNDARY;
+       }
+
+       ptr = (unsigned long)(ei + 1);
+
+       if (metadata && key.type == BTRFS_EXTENT_ITEM_KEY) {
+               /* Old EXTENT_ITEM metadata */
+               struct btrfs_tree_block_info *info;
+
+               info = (struct btrfs_tree_block_info *)ptr;
+               level = btrfs_tree_block_level(eb, info);
+               ptr += sizeof(struct btrfs_tree_block_info);
        } else {
-               stripe_size = length;
+               /* New METADATA_ITEM */
+               level = key.offset;
        }
-       return stripe_size;
+       end = (unsigned long)ei + item_size;
+
+       if (ptr >= end) {
+               err |= ITEM_SIZE_MISMATCH;
+               goto out;
+       }
+
+       /* Now check every backref in this extent item */
+next:
+       iref = (struct btrfs_extent_inline_ref *)ptr;
+       type = btrfs_extent_inline_ref_type(eb, iref);
+       offset = btrfs_extent_inline_ref_offset(eb, iref);
+       switch (type) {
+       case BTRFS_TREE_BLOCK_REF_KEY:
+               ret = check_tree_block_backref(fs_info, offset, key.objectid,
+                                              level);
+               err |= ret;
+               break;
+       case BTRFS_SHARED_BLOCK_REF_KEY:
+               ret = check_shared_block_backref(fs_info, offset, key.objectid,
+                                                level);
+               err |= ret;
+               break;
+       case BTRFS_EXTENT_DATA_REF_KEY:
+               dref = (struct btrfs_extent_data_ref *)(&iref->offset);
+               ret = check_extent_data_backref(fs_info,
+                               btrfs_extent_data_ref_root(eb, dref),
+                               btrfs_extent_data_ref_objectid(eb, dref),
+                               btrfs_extent_data_ref_offset(eb, dref),
+                               key.objectid, key.offset,
+                               btrfs_extent_data_ref_count(eb, dref));
+               err |= ret;
+               break;
+       case BTRFS_SHARED_DATA_REF_KEY:
+               ret = check_shared_data_backref(fs_info, offset, key.objectid);
+               err |= ret;
+               break;
+       default:
+               error("extent[%llu %d %llu] has unknown ref type: %d",
+                       key.objectid, key.type, key.offset, type);
+               err |= UNKNOWN_TYPE;
+               goto out;
+       }
+
+       ptr += btrfs_extent_inline_ref_size(type);
+       if (ptr < end)
+               goto next;
+
+out:
+       return err;
 }
 
 /*
- * Check the chunk with its block group/dev list ref:
- * Return 0 if all refs seems valid.
- * Return 1 if part of refs seems valid, need later check for rebuild ref
- * like missing block group and needs to search extent tree to rebuild them.
- * Return -1 if essential refs are missing and unable to rebuild.
+ * Check if a dev extent item is referred correctly by its chunk
  */
-static int check_chunk_refs(struct chunk_record *chunk_rec,
-                           struct block_group_tree *block_group_cache,
-                           struct device_extent_tree *dev_extent_cache,
-                           int silent)
+static int check_dev_extent_item(struct btrfs_fs_info *fs_info,
+                                struct extent_buffer *eb, int slot)
 {
-       struct cache_extent *block_group_item;
-       struct block_group_record *block_group_rec;
-       struct cache_extent *dev_extent_item;
-       struct device_extent_record *dev_extent_rec;
-       u64 devid;
-       u64 offset;
+       struct btrfs_root *chunk_root = fs_info->chunk_root;
+       struct btrfs_dev_extent *ptr;
+       struct btrfs_path path;
+       struct btrfs_key chunk_key;
+       struct btrfs_key devext_key;
+       struct btrfs_chunk *chunk;
+       struct extent_buffer *l;
+       int num_stripes;
        u64 length;
-       int metadump_v2 = 0;
        int i;
-       int ret = 0;
+       int found_chunk = 0;
+       int ret;
 
-       block_group_item = lookup_cache_extent(&block_group_cache->tree,
-                                              chunk_rec->offset,
-                                              chunk_rec->length);
-       if (block_group_item) {
-               block_group_rec = container_of(block_group_item,
-                                              struct block_group_record,
-                                              cache);
-               if (chunk_rec->length != block_group_rec->offset ||
-                   chunk_rec->offset != block_group_rec->objectid ||
-                   (!metadump_v2 &&
-                    chunk_rec->type_flags != block_group_rec->flags)) {
-                       if (!silent)
-                               fprintf(stderr,
-                                       "Chunk[%llu, %u, %llu]: length(%llu), offset(%llu), type(%llu) mismatch with block group[%llu, %u, %llu]: offset(%llu), objectid(%llu), flags(%llu)\n",
-                                       chunk_rec->objectid,
-                                       chunk_rec->type,
-                                       chunk_rec->offset,
-                                       chunk_rec->length,
-                                       chunk_rec->offset,
-                                       chunk_rec->type_flags,
-                                       block_group_rec->objectid,
-                                       block_group_rec->type,
-                                       block_group_rec->offset,
-                                       block_group_rec->offset,
-                                       block_group_rec->objectid,
-                                       block_group_rec->flags);
-                       ret = -1;
-               } else {
-                       list_del_init(&block_group_rec->list);
-                       chunk_rec->bg_rec = block_group_rec;
+       btrfs_item_key_to_cpu(eb, &devext_key, slot);
+       ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_extent);
+       length = btrfs_dev_extent_length(eb, ptr);
+
+       chunk_key.objectid = btrfs_dev_extent_chunk_objectid(eb, ptr);
+       chunk_key.type = BTRFS_CHUNK_ITEM_KEY;
+       chunk_key.offset = btrfs_dev_extent_chunk_offset(eb, ptr);
+
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, chunk_root, &chunk_key, &path, 0, 0);
+       if (ret)
+               goto out;
+
+       l = path.nodes[0];
+       chunk = btrfs_item_ptr(l, path.slots[0], struct btrfs_chunk);
+       if (btrfs_chunk_length(l, chunk) != length)
+               goto out;
+
+       num_stripes = btrfs_chunk_num_stripes(l, chunk);
+       for (i = 0; i < num_stripes; i++) {
+               u64 devid = btrfs_stripe_devid_nr(l, chunk, i);
+               u64 offset = btrfs_stripe_offset_nr(l, chunk, i);
+
+               if (devid == devext_key.objectid &&
+                   offset == devext_key.offset) {
+                       found_chunk = 1;
+                       break;
                }
-       } else {
-               if (!silent)
-                       fprintf(stderr,
-                               "Chunk[%llu, %u, %llu]: length(%llu), offset(%llu), type(%llu) is not found in block group\n",
-                               chunk_rec->objectid,
-                               chunk_rec->type,
-                               chunk_rec->offset,
-                               chunk_rec->length,
-                               chunk_rec->offset,
-                               chunk_rec->type_flags);
-               ret = 1;
        }
+out:
+       btrfs_release_path(&path);
+       if (!found_chunk) {
+               error(
+               "device extent[%llu, %llu, %llu] did not find the related chunk",
+                       devext_key.objectid, devext_key.offset, length);
+               return REFERENCER_MISSING;
+       }
+       return 0;
+}
 
-       if (metadump_v2)
-               return ret;
+/*
+ * Check if the used space is correct with the dev item
+ */
+static int check_dev_item(struct btrfs_fs_info *fs_info,
+                         struct extent_buffer *eb, int slot)
+{
+       struct btrfs_root *dev_root = fs_info->dev_root;
+       struct btrfs_dev_item *dev_item;
+       struct btrfs_path path;
+       struct btrfs_key key;
+       struct btrfs_dev_extent *ptr;
+       u64 dev_id;
+       u64 used;
+       u64 total = 0;
+       int ret;
 
-       length = calc_stripe_length(chunk_rec->type_flags, chunk_rec->length,
-                                   chunk_rec->num_stripes);
-       for (i = 0; i < chunk_rec->num_stripes; ++i) {
-               devid = chunk_rec->stripes[i].devid;
-               offset = chunk_rec->stripes[i].offset;
-               dev_extent_item = lookup_cache_extent2(&dev_extent_cache->tree,
-                                                      devid, offset, length);
-               if (dev_extent_item) {
-                       dev_extent_rec = container_of(dev_extent_item,
-                                               struct device_extent_record,
-                                               cache);
-                       if (dev_extent_rec->objectid != devid ||
-                           dev_extent_rec->offset != offset ||
-                           dev_extent_rec->chunk_offset != chunk_rec->offset ||
-                           dev_extent_rec->length != length) {
-                               if (!silent)
-                                       fprintf(stderr,
-                                               "Chunk[%llu, %u, %llu] stripe[%llu, %llu] dismatch dev extent[%llu, %llu, %llu]\n",
-                                               chunk_rec->objectid,
-                                               chunk_rec->type,
-                                               chunk_rec->offset,
-                                               chunk_rec->stripes[i].devid,
-                                               chunk_rec->stripes[i].offset,
-                                               dev_extent_rec->objectid,
-                                               dev_extent_rec->offset,
-                                               dev_extent_rec->length);
-                               ret = -1;
-                       } else {
-                               list_move(&dev_extent_rec->chunk_list,
-                                         &chunk_rec->dextents);
-                       }
-               } else {
-                       if (!silent)
-                               fprintf(stderr,
-                                       "Chunk[%llu, %u, %llu] stripe[%llu, %llu] is not found in dev extent\n",
-                                       chunk_rec->objectid,
-                                       chunk_rec->type,
-                                       chunk_rec->offset,
-                                       chunk_rec->stripes[i].devid,
-                                       chunk_rec->stripes[i].offset);
-                       ret = -1;
-               }
+       dev_item = btrfs_item_ptr(eb, slot, struct btrfs_dev_item);
+       dev_id = btrfs_device_id(eb, dev_item);
+       used = btrfs_device_bytes_used(eb, dev_item);
+
+       key.objectid = dev_id;
+       key.type = BTRFS_DEV_EXTENT_KEY;
+       key.offset = 0;
+
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, dev_root, &key, &path, 0, 0);
+       if (ret < 0) {
+               btrfs_item_key_to_cpu(eb, &key, slot);
+               error("cannot find any related dev extent for dev[%llu, %u, %llu]",
+                       key.objectid, key.type, key.offset);
+               btrfs_release_path(&path);
+               return REFERENCER_MISSING;
        }
-       return ret;
+
+       /* Iterate dev_extents to calculate the used space of a device */
+       while (1) {
+               btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+
+               if (key.objectid > dev_id)
+                       break;
+               if (key.type != BTRFS_DEV_EXTENT_KEY || key.objectid != dev_id)
+                       goto next;
+
+               ptr = btrfs_item_ptr(path.nodes[0], path.slots[0],
+                                    struct btrfs_dev_extent);
+               total += btrfs_dev_extent_length(path.nodes[0], ptr);
+next:
+               ret = btrfs_next_item(dev_root, &path);
+               if (ret)
+                       break;
+       }
+       btrfs_release_path(&path);
+
+       if (used != total) {
+               btrfs_item_key_to_cpu(eb, &key, slot);
+               error(
+"Dev extent's total-byte %llu is not equal to bytes-used %llu in dev[%llu, %u, %llu]",
+                       total, used, BTRFS_ROOT_TREE_OBJECTID,
+                       BTRFS_DEV_EXTENT_KEY, dev_id);
+               return ACCOUNTING_MISMATCH;
+       }
+       return 0;
 }
 
-/* check btrfs_chunk -> btrfs_dev_extent / btrfs_block_group_item */
-int check_chunks(struct cache_tree *chunk_cache,
-                struct block_group_tree *block_group_cache,
-                struct device_extent_tree *dev_extent_cache,
-                struct list_head *good, struct list_head *bad,
-                struct list_head *rebuild, int silent)
+/*
+ * Check a block group item with its referener (chunk) and its used space
+ * with extent/metadata item
+ */
+static int check_block_group_item(struct btrfs_fs_info *fs_info,
+                                 struct extent_buffer *eb, int slot)
 {
-       struct cache_extent *chunk_item;
-       struct chunk_record *chunk_rec;
-       struct block_group_record *bg_rec;
-       struct device_extent_record *dext_rec;
-       int err;
-       int ret = 0;
+       struct btrfs_root *extent_root = fs_info->extent_root;
+       struct btrfs_root *chunk_root = fs_info->chunk_root;
+       struct btrfs_block_group_item *bi;
+       struct btrfs_block_group_item bg_item;
+       struct btrfs_path path;
+       struct btrfs_key bg_key;
+       struct btrfs_key chunk_key;
+       struct btrfs_key extent_key;
+       struct btrfs_chunk *chunk;
+       struct extent_buffer *leaf;
+       struct btrfs_extent_item *ei;
+       u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       u64 flags;
+       u64 bg_flags;
+       u64 used;
+       u64 total = 0;
+       int ret;
+       int err = 0;
 
-       chunk_item = first_cache_extent(chunk_cache);
-       while (chunk_item) {
-               chunk_rec = container_of(chunk_item, struct chunk_record,
-                                        cache);
-               err = check_chunk_refs(chunk_rec, block_group_cache,
-                                      dev_extent_cache, silent);
-               if (err < 0)
-                       ret = err;
-               if (err == 0 && good)
-                       list_add_tail(&chunk_rec->list, good);
-               if (err > 0 && rebuild)
-                       list_add_tail(&chunk_rec->list, rebuild);
-               if (err < 0 && bad)
-                       list_add_tail(&chunk_rec->list, bad);
-               chunk_item = next_cache_extent(chunk_item);
-       }
+       btrfs_item_key_to_cpu(eb, &bg_key, slot);
+       bi = btrfs_item_ptr(eb, slot, struct btrfs_block_group_item);
+       read_extent_buffer(eb, &bg_item, (unsigned long)bi, sizeof(bg_item));
+       used = btrfs_block_group_used(&bg_item);
+       bg_flags = btrfs_block_group_flags(&bg_item);
 
-       list_for_each_entry(bg_rec, &block_group_cache->block_groups, list) {
-               if (!silent)
-                       fprintf(stderr,
-                               "Block group[%llu, %llu] (flags = %llu) didn't find the relative chunk.\n",
-                               bg_rec->objectid,
-                               bg_rec->offset,
-                               bg_rec->flags);
-               if (!ret)
-                       ret = 1;
-       }
+       chunk_key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+       chunk_key.type = BTRFS_CHUNK_ITEM_KEY;
+       chunk_key.offset = bg_key.objectid;
 
-       list_for_each_entry(dext_rec, &dev_extent_cache->no_chunk_orphans,
-                           chunk_list) {
-               if (!silent)
-                       fprintf(stderr,
-                               "Device extent[%llu, %llu, %llu] didn't find the relative chunk.\n",
-                               dext_rec->objectid,
-                               dext_rec->offset,
-                               dext_rec->length);
-               if (!ret)
-                       ret = 1;
+       btrfs_init_path(&path);
+       /* Search for the referencer chunk */
+       ret = btrfs_search_slot(NULL, chunk_root, &chunk_key, &path, 0, 0);
+       if (ret) {
+               error(
+               "block group[%llu %llu] did not find the related chunk item",
+                       bg_key.objectid, bg_key.offset);
+               err |= REFERENCER_MISSING;
+       } else {
+               chunk = btrfs_item_ptr(path.nodes[0], path.slots[0],
+                                       struct btrfs_chunk);
+               if (btrfs_chunk_length(path.nodes[0], chunk) !=
+                                               bg_key.offset) {
+                       error(
+       "block group[%llu %llu] related chunk item length does not match",
+                               bg_key.objectid, bg_key.offset);
+                       err |= REFERENCER_MISMATCH;
+               }
        }
-       return ret;
-}
+       btrfs_release_path(&path);
 
+       /* Search from the block group bytenr */
+       extent_key.objectid = bg_key.objectid;
+       extent_key.type = 0;
+       extent_key.offset = 0;
 
-static int check_device_used(struct device_record *dev_rec,
-                            struct device_extent_tree *dext_cache)
-{
-       struct cache_extent *cache;
-       struct device_extent_record *dev_extent_rec;
-       u64 total_byte = 0;
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, extent_root, &extent_key, &path, 0, 0);
+       if (ret < 0)
+               goto out;
 
-       cache = search_cache_extent2(&dext_cache->tree, dev_rec->devid, 0);
-       while (cache) {
-               dev_extent_rec = container_of(cache,
-                                             struct device_extent_record,
-                                             cache);
-               if (dev_extent_rec->objectid != dev_rec->devid)
+       /* Iterate extent tree to account used space */
+       while (1) {
+               leaf = path.nodes[0];
+               btrfs_item_key_to_cpu(leaf, &extent_key, path.slots[0]);
+               if (extent_key.objectid >= bg_key.objectid + bg_key.offset)
                        break;
 
-               list_del_init(&dev_extent_rec->device_list);
-               total_byte += dev_extent_rec->length;
-               cache = next_cache_extent(cache);
+               if (extent_key.type != BTRFS_METADATA_ITEM_KEY &&
+                   extent_key.type != BTRFS_EXTENT_ITEM_KEY)
+                       goto next;
+               if (extent_key.objectid < bg_key.objectid)
+                       goto next;
+
+               if (extent_key.type == BTRFS_METADATA_ITEM_KEY)
+                       total += nodesize;
+               else
+                       total += extent_key.offset;
+
+               ei = btrfs_item_ptr(leaf, path.slots[0],
+                                   struct btrfs_extent_item);
+               flags = btrfs_extent_flags(leaf, ei);
+               if (flags & BTRFS_EXTENT_FLAG_DATA) {
+                       if (!(bg_flags & BTRFS_BLOCK_GROUP_DATA)) {
+                               error(
+                       "bad extent[%llu, %llu) type mismatch with chunk",
+                                       extent_key.objectid,
+                                       extent_key.objectid + extent_key.offset);
+                               err |= CHUNK_TYPE_MISMATCH;
+                       }
+               } else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
+                       if (!(bg_flags & (BTRFS_BLOCK_GROUP_SYSTEM |
+                                   BTRFS_BLOCK_GROUP_METADATA))) {
+                               error(
+                       "bad extent[%llu, %llu) type mismatch with chunk",
+                                       extent_key.objectid,
+                                       extent_key.objectid + nodesize);
+                               err |= CHUNK_TYPE_MISMATCH;
+                       }
+               }
+next:
+               ret = btrfs_next_item(extent_root, &path);
+               if (ret)
+                       break;
        }
 
-       if (total_byte != dev_rec->byte_used) {
-               fprintf(stderr,
-                       "Dev extent's total-byte(%llu) is not equal to byte-used(%llu) in dev[%llu, %u, %llu]\n",
-                       total_byte, dev_rec->byte_used, dev_rec->objectid,
-                       dev_rec->type, dev_rec->offset);
-               return -1;
-       } else {
-               return 0;
+out:
+       btrfs_release_path(&path);
+
+       if (total != used) {
+               error(
+               "block group[%llu %llu] used %llu but extent items used %llu",
+                       bg_key.objectid, bg_key.offset, used, total);
+               err |= ACCOUNTING_MISMATCH;
        }
+       return err;
 }
 
-/* check btrfs_dev_item -> btrfs_dev_extent */
-static int check_devices(struct rb_root *dev_cache,
-                        struct device_extent_tree *dev_extent_cache)
+/*
+ * Check a chunk item.
+ * Including checking all referred dev_extents and block group
+ */
+static int check_chunk_item(struct btrfs_fs_info *fs_info,
+                           struct extent_buffer *eb, int slot)
 {
-       struct rb_node *dev_node;
-       struct device_record *dev_rec;
-       struct device_extent_record *dext_rec;
-       int err;
-       int ret = 0;
+       struct btrfs_root *extent_root = fs_info->extent_root;
+       struct btrfs_root *dev_root = fs_info->dev_root;
+       struct btrfs_path path;
+       struct btrfs_key chunk_key;
+       struct btrfs_key bg_key;
+       struct btrfs_key devext_key;
+       struct btrfs_chunk *chunk;
+       struct extent_buffer *leaf;
+       struct btrfs_block_group_item *bi;
+       struct btrfs_block_group_item bg_item;
+       struct btrfs_dev_extent *ptr;
+       u32 sectorsize = btrfs_super_sectorsize(fs_info->super_copy);
+       u64 length;
+       u64 chunk_end;
+       u64 type;
+       u64 profile;
+       int num_stripes;
+       u64 offset;
+       u64 objectid;
+       int i;
+       int ret;
+       int err = 0;
 
-       dev_node = rb_first(dev_cache);
-       while (dev_node) {
-               dev_rec = container_of(dev_node, struct device_record, node);
-               err = check_device_used(dev_rec, dev_extent_cache);
-               if (err)
-                       ret = err;
+       btrfs_item_key_to_cpu(eb, &chunk_key, slot);
+       chunk = btrfs_item_ptr(eb, slot, struct btrfs_chunk);
+       length = btrfs_chunk_length(eb, chunk);
+       chunk_end = chunk_key.offset + length;
+       if (!IS_ALIGNED(length, sectorsize)) {
+               error("chunk[%llu %llu) not aligned to %u",
+                       chunk_key.offset, chunk_end, sectorsize);
+               err |= BYTES_UNALIGNED;
+               goto out;
+       }
 
-               dev_node = rb_next(dev_node);
+       type = btrfs_chunk_type(eb, chunk);
+       profile = type & BTRFS_BLOCK_GROUP_PROFILE_MASK;
+       if (!(type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
+               error("chunk[%llu %llu) has no chunk type",
+                       chunk_key.offset, chunk_end);
+               err |= UNKNOWN_TYPE;
        }
-       list_for_each_entry(dext_rec, &dev_extent_cache->no_device_orphans,
-                           device_list) {
-               fprintf(stderr,
-                       "Device extent[%llu, %llu, %llu] didn't find its device.\n",
-                       dext_rec->objectid, dext_rec->offset, dext_rec->length);
-               if (!ret)
-                       ret = 1;
+       if (profile && (profile & (profile - 1))) {
+               error("chunk[%llu %llu) multiple profiles detected: %llx",
+                       chunk_key.offset, chunk_end, profile);
+               err |= UNKNOWN_TYPE;
        }
-       return ret;
-}
 
-static int add_root_item_to_list(struct list_head *head,
-                                 u64 objectid, u64 bytenr, u64 last_snapshot,
-                                 u8 level, u8 drop_level,
-                                 int level_size, struct btrfs_key *drop_key)
-{
+       bg_key.objectid = chunk_key.offset;
+       bg_key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+       bg_key.offset = length;
 
-       struct root_item_record *ri_rec;
-       ri_rec = malloc(sizeof(*ri_rec));
-       if (!ri_rec)
-               return -ENOMEM;
-       ri_rec->bytenr = bytenr;
-       ri_rec->objectid = objectid;
-       ri_rec->level = level;
-       ri_rec->level_size = level_size;
-       ri_rec->drop_level = drop_level;
-       ri_rec->last_snapshot = last_snapshot;
-       if (drop_key)
-               memcpy(&ri_rec->drop_key, drop_key, sizeof(*drop_key));
-       list_add_tail(&ri_rec->list, head);
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, extent_root, &bg_key, &path, 0, 0);
+       if (ret) {
+               error(
+               "chunk[%llu %llu) did not find the related block group item",
+                       chunk_key.offset, chunk_end);
+               err |= REFERENCER_MISSING;
+       } else{
+               leaf = path.nodes[0];
+               bi = btrfs_item_ptr(leaf, path.slots[0],
+                                   struct btrfs_block_group_item);
+               read_extent_buffer(leaf, &bg_item, (unsigned long)bi,
+                                  sizeof(bg_item));
+               if (btrfs_block_group_flags(&bg_item) != type) {
+                       error(
+"chunk[%llu %llu) related block group item flags mismatch, wanted: %llu, have: %llu",
+                               chunk_key.offset, chunk_end, type,
+                               btrfs_block_group_flags(&bg_item));
+                       err |= REFERENCER_MISSING;
+               }
+       }
 
-       return 0;
-}
+       num_stripes = btrfs_chunk_num_stripes(eb, chunk);
+       for (i = 0; i < num_stripes; i++) {
+               btrfs_release_path(&path);
+               btrfs_init_path(&path);
+               devext_key.objectid = btrfs_stripe_devid_nr(eb, chunk, i);
+               devext_key.type = BTRFS_DEV_EXTENT_KEY;
+               devext_key.offset = btrfs_stripe_offset_nr(eb, chunk, i);
 
-static void free_root_item_list(struct list_head *list)
-{
-       struct root_item_record *ri_rec;
+               ret = btrfs_search_slot(NULL, dev_root, &devext_key, &path,
+                                       0, 0);
+               if (ret)
+                       goto not_match_dev;
 
-       while (!list_empty(list)) {
-               ri_rec = list_first_entry(list, struct root_item_record,
-                                         list);
-               list_del_init(&ri_rec->list);
-               free(ri_rec);
+               leaf = path.nodes[0];
+               ptr = btrfs_item_ptr(leaf, path.slots[0],
+                                    struct btrfs_dev_extent);
+               objectid = btrfs_dev_extent_chunk_objectid(leaf, ptr);
+               offset = btrfs_dev_extent_chunk_offset(leaf, ptr);
+               if (objectid != chunk_key.objectid ||
+                   offset != chunk_key.offset ||
+                   btrfs_dev_extent_length(leaf, ptr) != length)
+                       goto not_match_dev;
+               continue;
+not_match_dev:
+               err |= BACKREF_MISSING;
+               error(
+               "chunk[%llu %llu) stripe %d did not find the related dev extent",
+                       chunk_key.objectid, chunk_end, i);
+               continue;
        }
+       btrfs_release_path(&path);
+out:
+       return err;
 }
 
-static int deal_root_from_list(struct list_head *list,
-                              struct btrfs_root *root,
-                              struct block_info *bits,
-                              int bits_nr,
-                              struct cache_tree *pending,
-                              struct cache_tree *seen,
-                              struct cache_tree *reada,
-                              struct cache_tree *nodes,
-                              struct cache_tree *extent_cache,
-                              struct cache_tree *chunk_cache,
-                              struct rb_root *dev_cache,
-                              struct block_group_tree *block_group_cache,
-                              struct device_extent_tree *dev_extent_cache)
+/*
+ * Main entry function to check known items and update related accounting info
+ */
+static int check_leaf_items(struct btrfs_root *root, struct extent_buffer *eb)
 {
-       int ret = 0;
-       u64 last;
+       struct btrfs_fs_info *fs_info = root->fs_info;
+       struct btrfs_key key;
+       int slot = 0;
+       int type;
+       struct btrfs_extent_data_ref *dref;
+       int ret;
+       int err = 0;
 
-       while (!list_empty(list)) {
-               struct root_item_record *rec;
-               struct extent_buffer *buf;
-               rec = list_entry(list->next,
-                                struct root_item_record, list);
-               last = 0;
-               buf = read_tree_block(root->fs_info->tree_root,
-                                     rec->bytenr, rec->level_size, 0);
-               if (!extent_buffer_uptodate(buf)) {
-                       free_extent_buffer(buf);
-                       ret = -EIO;
-                       break;
-               }
-               add_root_to_pending(buf, extent_cache, pending,
-                                   seen, nodes, rec->objectid);
-               /*
-                * To rebuild extent tree, we need deal with snapshot
-                * one by one, otherwise we deal with node firstly which
-                * can maximize readahead.
-                */
-               while (1) {
-                       ret = run_next_block(root, bits, bits_nr, &last,
-                                            pending, seen, reada, nodes,
-                                            extent_cache, chunk_cache,
-                                            dev_cache, block_group_cache,
-                                            dev_extent_cache, rec);
-                       if (ret != 0)
-                               break;
-               }
-               free_extent_buffer(buf);
-               list_del(&rec->list);
-               free(rec);
-               if (ret < 0)
-                       break;
-       }
-       while (ret >= 0) {
-               ret = run_next_block(root, bits, bits_nr, &last, pending, seen,
-                                    reada, nodes, extent_cache, chunk_cache,
-                                    dev_cache, block_group_cache,
-                                    dev_extent_cache, NULL);
-               if (ret != 0) {
-                       if (ret > 0)
-                               ret = 0;
-                       break;
-               }
-       }
-       return ret;
+next:
+       btrfs_item_key_to_cpu(eb, &key, slot);
+       type = key.type;
+
+       switch (type) {
+       case BTRFS_EXTENT_DATA_KEY:
+               ret = check_extent_data_item(root, eb, slot);
+               err |= ret;
+               break;
+       case BTRFS_BLOCK_GROUP_ITEM_KEY:
+               ret = check_block_group_item(fs_info, eb, slot);
+               err |= ret;
+               break;
+       case BTRFS_DEV_ITEM_KEY:
+               ret = check_dev_item(fs_info, eb, slot);
+               err |= ret;
+               break;
+       case BTRFS_CHUNK_ITEM_KEY:
+               ret = check_chunk_item(fs_info, eb, slot);
+               err |= ret;
+               break;
+       case BTRFS_DEV_EXTENT_KEY:
+               ret = check_dev_extent_item(fs_info, eb, slot);
+               err |= ret;
+               break;
+       case BTRFS_EXTENT_ITEM_KEY:
+       case BTRFS_METADATA_ITEM_KEY:
+               ret = check_extent_item(fs_info, eb, slot);
+               err |= ret;
+               break;
+       case BTRFS_EXTENT_CSUM_KEY:
+               total_csum_bytes += btrfs_item_size_nr(eb, slot);
+               break;
+       case BTRFS_TREE_BLOCK_REF_KEY:
+               ret = check_tree_block_backref(fs_info, key.offset,
+                                              key.objectid, -1);
+               err |= ret;
+               break;
+       case BTRFS_EXTENT_DATA_REF_KEY:
+               dref = btrfs_item_ptr(eb, slot, struct btrfs_extent_data_ref);
+               ret = check_extent_data_backref(fs_info,
+                               btrfs_extent_data_ref_root(eb, dref),
+                               btrfs_extent_data_ref_objectid(eb, dref),
+                               btrfs_extent_data_ref_offset(eb, dref),
+                               key.objectid, 0,
+                               btrfs_extent_data_ref_count(eb, dref));
+               err |= ret;
+               break;
+       case BTRFS_SHARED_BLOCK_REF_KEY:
+               ret = check_shared_block_backref(fs_info, key.offset,
+                                                key.objectid, -1);
+               err |= ret;
+               break;
+       case BTRFS_SHARED_DATA_REF_KEY:
+               ret = check_shared_data_backref(fs_info, key.offset,
+                                               key.objectid);
+               err |= ret;
+               break;
+       default:
+               break;
+       }
+
+       if (++slot < btrfs_header_nritems(eb))
+               goto next;
+
+       return err;
 }
 
-static int check_chunks_and_extents(struct btrfs_root *root)
+/*
+ * Helper function for later fs/subvol tree check.  To determine if a tree
+ * block should be checked.
+ * This function will ensure only the direct referencer with lowest rootid to
+ * check a fs/subvolume tree block.
+ *
+ * Backref check at extent tree would detect errors like missing subvolume
+ * tree, so we can do aggressive check to reduce duplicated checks.
+ */
+static int should_check(struct btrfs_root *root, struct extent_buffer *eb)
 {
-       struct rb_root dev_cache;
-       struct cache_tree chunk_cache;
-       struct block_group_tree block_group_cache;
-       struct device_extent_tree dev_extent_cache;
-       struct cache_tree extent_cache;
-       struct cache_tree seen;
-       struct cache_tree pending;
-       struct cache_tree reada;
-       struct cache_tree nodes;
-       struct extent_io_tree excluded_extents;
-       struct cache_tree corrupt_blocks;
-       struct btrfs_path path;
+       struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct btrfs_key key;
-       struct btrfs_key found_key;
-       int ret, err = 0;
-       struct block_info *bits;
-       int bits_nr;
+       struct btrfs_path path;
        struct extent_buffer *leaf;
        int slot;
-       struct btrfs_root_item ri;
-       struct list_head dropping_trees;
-       struct list_head normal_trees;
-       struct btrfs_root *root1;
-       u64 objectid;
-       u32 level_size;
-       u8 level;
+       struct btrfs_extent_item *ei;
+       unsigned long ptr;
+       unsigned long end;
+       int type;
+       u32 item_size;
+       u64 offset;
+       struct btrfs_extent_inline_ref *iref;
+       int ret;
 
-       dev_cache = RB_ROOT;
-       cache_tree_init(&chunk_cache);
-       block_group_tree_init(&block_group_cache);
-       device_extent_tree_init(&dev_extent_cache);
+       btrfs_init_path(&path);
+       key.objectid = btrfs_header_bytenr(eb);
+       key.type = BTRFS_METADATA_ITEM_KEY;
+       key.offset = (u64)-1;
 
-       cache_tree_init(&extent_cache);
-       cache_tree_init(&seen);
-       cache_tree_init(&pending);
-       cache_tree_init(&nodes);
-       cache_tree_init(&reada);
-       cache_tree_init(&corrupt_blocks);
-       extent_io_tree_init(&excluded_extents);
-       INIT_LIST_HEAD(&dropping_trees);
-       INIT_LIST_HEAD(&normal_trees);
+       /*
+        * Any failure in backref resolving means we can't determine
+        * whom the tree block belongs to.
+        * So in that case, we need to check that tree block
+        */
+       ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
+       if (ret < 0)
+               goto need_check;
 
-       if (repair) {
-               root->fs_info->excluded_extents = &excluded_extents;
-               root->fs_info->fsck_extent_cache = &extent_cache;
-               root->fs_info->free_extent_hook = free_extent_hook;
-               root->fs_info->corrupt_blocks = &corrupt_blocks;
-       }
+       ret = btrfs_previous_extent_item(extent_root, &path,
+                                        btrfs_header_bytenr(eb));
+       if (ret)
+               goto need_check;
 
-       bits_nr = 1024;
-       bits = malloc(bits_nr * sizeof(struct block_info));
-       if (!bits) {
-               perror("malloc");
-               exit(1);
-       }
+       leaf = path.nodes[0];
+       slot = path.slots[0];
+       btrfs_item_key_to_cpu(leaf, &key, slot);
+       ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 
-       if (ctx.progress_enabled) {
-               ctx.tp = TASK_EXTENTS;
-               task_start(ctx.info);
+       if (key.type == BTRFS_METADATA_ITEM_KEY) {
+               iref = (struct btrfs_extent_inline_ref *)(ei + 1);
+       } else {
+               struct btrfs_tree_block_info *info;
+
+               info = (struct btrfs_tree_block_info *)(ei + 1);
+               iref = (struct btrfs_extent_inline_ref *)(info + 1);
        }
 
-again:
-       root1 = root->fs_info->tree_root;
-       level = btrfs_header_level(root1->node);
-       ret = add_root_item_to_list(&normal_trees, root1->root_key.objectid,
-                                   root1->node->start, 0, level, 0,
-                                   root1->nodesize, NULL);
-       if (ret < 0)
-               goto out;
-       root1 = root->fs_info->chunk_root;
-       level = btrfs_header_level(root1->node);
-       ret = add_root_item_to_list(&normal_trees, root1->root_key.objectid,
-                                   root1->node->start, 0, level, 0,
-                                   root1->nodesize, NULL);
-       if (ret < 0)
-               goto out;
-       btrfs_init_path(&path);
-       key.offset = 0;
-       key.objectid = 0;
-       btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
-       ret = btrfs_search_slot(NULL, root->fs_info->tree_root,
-                                       &key, &path, 0, 0);
-       if (ret < 0)
-               goto out;
-       while(1) {
-               leaf = path.nodes[0];
-               slot = path.slots[0];
-               if (slot >= btrfs_header_nritems(path.nodes[0])) {
-                       ret = btrfs_next_leaf(root, &path);
-                       if (ret != 0)
-                               break;
-                       leaf = path.nodes[0];
-                       slot = path.slots[0];
-               }
-               btrfs_item_key_to_cpu(leaf, &found_key, path.slots[0]);
-               if (btrfs_key_type(&found_key) == BTRFS_ROOT_ITEM_KEY) {
-                       unsigned long offset;
-                       u64 last_snapshot;
+       item_size = btrfs_item_size_nr(leaf, slot);
+       ptr = (unsigned long)iref;
+       end = (unsigned long)ei + item_size;
+       while (ptr < end) {
+               iref = (struct btrfs_extent_inline_ref *)ptr;
+               type = btrfs_extent_inline_ref_type(leaf, iref);
+               offset = btrfs_extent_inline_ref_offset(leaf, iref);
 
-                       offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
-                       read_extent_buffer(leaf, &ri, offset, sizeof(ri));
-                       last_snapshot = btrfs_root_last_snapshot(&ri);
-                       if (btrfs_disk_key_objectid(&ri.drop_progress) == 0) {
-                               level = btrfs_root_level(&ri);
-                               level_size = root->nodesize;
-                               ret = add_root_item_to_list(&normal_trees,
-                                               found_key.objectid,
-                                               btrfs_root_bytenr(&ri),
-                                               last_snapshot, level,
-                                               0, level_size, NULL);
-                               if (ret < 0)
-                                       goto out;
-                       } else {
-                               level = btrfs_root_level(&ri);
-                               level_size = root->nodesize;
-                               objectid = found_key.objectid;
-                               btrfs_disk_key_to_cpu(&found_key,
-                                                     &ri.drop_progress);
-                               ret = add_root_item_to_list(&dropping_trees,
-                                               objectid,
-                                               btrfs_root_bytenr(&ri),
-                                               last_snapshot, level,
-                                               ri.drop_level,
-                                               level_size, &found_key);
-                               if (ret < 0)
-                                       goto out;
-                       }
+               /*
+                * We only check the tree block if current root is
+                * the lowest referencer of it.
+                */
+               if (type == BTRFS_TREE_BLOCK_REF_KEY &&
+                   offset < root->objectid) {
+                       btrfs_release_path(&path);
+                       return 0;
                }
-               path.slots[0]++;
+
+               ptr += btrfs_extent_inline_ref_size(type);
        }
+       /*
+        * Normally we should also check keyed tree block ref, but that may be
+        * very time consuming.  Inlined ref should already make us skip a lot
+        * of refs now.  So skip search keyed tree block ref.
+        */
+
+need_check:
        btrfs_release_path(&path);
+       return 1;
+}
+
+/*
+ * Traversal function for tree block. We will do:
+ * 1) Skip shared fs/subvolume tree blocks
+ * 2) Update related bytes accounting
+ * 3) Pre-order traversal
+ */
+static int traverse_tree_block(struct btrfs_root *root,
+                               struct extent_buffer *node)
+{
+       struct extent_buffer *eb;
+       struct btrfs_key key;
+       struct btrfs_key drop_key;
+       int level;
+       u64 nr;
+       int i;
+       int err = 0;
+       int ret;
 
        /*
-        * check_block can return -EAGAIN if it fixes something, please keep
-        * this in mind when dealing with return values from these functions, if
-        * we get -EAGAIN we want to fall through and restart the loop.
+        * Skip shared fs/subvolume tree block, in that case they will
+        * be checked by referencer with lowest rootid
         */
-       ret = deal_root_from_list(&normal_trees, root, bits, bits_nr, &pending,
-                                 &seen, &reada, &nodes, &extent_cache,
-                                 &chunk_cache, &dev_cache, &block_group_cache,
-                                 &dev_extent_cache);
-       if (ret < 0) {
-               if (ret == -EAGAIN)
-                       goto loop;
-               goto out;
-       }
-       ret = deal_root_from_list(&dropping_trees, root, bits, bits_nr,
-                                 &pending, &seen, &reada, &nodes,
-                                 &extent_cache, &chunk_cache, &dev_cache,
-                                 &block_group_cache, &dev_extent_cache);
-       if (ret < 0) {
-               if (ret == -EAGAIN)
-                       goto loop;
-               goto out;
+       if (is_fstree(root->objectid) && !should_check(root, node))
+               return 0;
+
+       /* Update bytes accounting */
+       total_btree_bytes += node->len;
+       if (fs_root_objectid(btrfs_header_owner(node)))
+               total_fs_tree_bytes += node->len;
+       if (btrfs_header_owner(node) == BTRFS_EXTENT_TREE_OBJECTID)
+               total_extent_tree_bytes += node->len;
+       if (!found_old_backref &&
+           btrfs_header_owner(node) == BTRFS_TREE_RELOC_OBJECTID &&
+           btrfs_header_backref_rev(node) == BTRFS_MIXED_BACKREF_REV &&
+           !btrfs_header_flag(node, BTRFS_HEADER_FLAG_RELOC))
+               found_old_backref = 1;
+
+       /* pre-order tranversal, check itself first */
+       level = btrfs_header_level(node);
+       ret = check_tree_block_ref(root, node, btrfs_header_bytenr(node),
+                                  btrfs_header_level(node),
+                                  btrfs_header_owner(node));
+       err |= ret;
+       if (err)
+               error(
+       "check %s failed root %llu bytenr %llu level %d, force continue check",
+                       level ? "node":"leaf", root->objectid,
+                       btrfs_header_bytenr(node), btrfs_header_level(node));
+
+       if (!level) {
+               btree_space_waste += btrfs_leaf_free_space(root, node);
+               ret = check_leaf_items(root, node);
+               err |= ret;
+               return err;
        }
 
-       ret = check_chunks(&chunk_cache, &block_group_cache,
-                          &dev_extent_cache, NULL, NULL, NULL, 0);
-       if (ret) {
-               if (ret == -EAGAIN)
-                       goto loop;
-               err = ret;
+       nr = btrfs_header_nritems(node);
+       btrfs_disk_key_to_cpu(&drop_key, &root->root_item.drop_progress);
+       btree_space_waste += (BTRFS_NODEPTRS_PER_BLOCK(root) - nr) *
+               sizeof(struct btrfs_key_ptr);
+
+       /* Then check all its children */
+       for (i = 0; i < nr; i++) {
+               u64 blocknr = btrfs_node_blockptr(node, i);
+
+               btrfs_node_key_to_cpu(node, &key, i);
+               if (level == root->root_item.drop_level &&
+                   is_dropped_key(&key, &drop_key))
+                       continue;
+
+               /*
+                * As a btrfs tree has most 8 levels (0..7), so it's quite safe
+                * to call the function itself.
+                */
+               eb = read_tree_block(root, blocknr, root->nodesize, 0);
+               if (extent_buffer_uptodate(eb)) {
+                       ret = traverse_tree_block(root, eb);
+                       err |= ret;
+               }
+               free_extent_buffer(eb);
        }
 
-       ret = check_extent_refs(root, &extent_cache);
-       if (ret < 0) {
-               if (ret == -EAGAIN)
-                       goto loop;
+       return err;
+}
+
+/*
+ * Low memory usage version check_chunks_and_extents.
+ */
+static int check_chunks_and_extents_v2(struct btrfs_root *root)
+{
+       struct btrfs_path path;
+       struct btrfs_key key;
+       struct btrfs_root *root1;
+       struct btrfs_root *cur_root;
+       int err = 0;
+       int ret;
+
+       root1 = root->fs_info->chunk_root;
+       ret = traverse_tree_block(root1, root1->node);
+       err |= ret;
+
+       root1 = root->fs_info->tree_root;
+       ret = traverse_tree_block(root1, root1->node);
+       err |= ret;
+
+       btrfs_init_path(&path);
+       key.objectid = BTRFS_EXTENT_TREE_OBJECTID;
+       key.offset = 0;
+       key.type = BTRFS_ROOT_ITEM_KEY;
+
+       ret = btrfs_search_slot(NULL, root1, &key, &path, 0, 0);
+       if (ret) {
+               error("cannot find extent treet in tree_root");
                goto out;
        }
 
-       ret = check_devices(&dev_cache, &dev_extent_cache);
-       if (ret && err)
-               ret = err;
+       while (1) {
+               btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+               if (key.type != BTRFS_ROOT_ITEM_KEY)
+                       goto next;
+               key.offset = (u64)-1;
 
-out:
-       task_stop(ctx.info);
-       if (repair) {
-               free_corrupt_blocks_tree(root->fs_info->corrupt_blocks);
-               extent_io_tree_cleanup(&excluded_extents);
-               root->fs_info->fsck_extent_cache = NULL;
-               root->fs_info->free_extent_hook = NULL;
-               root->fs_info->corrupt_blocks = NULL;
-               root->fs_info->excluded_extents = NULL;
+               cur_root = btrfs_read_fs_root(root->fs_info, &key);
+               if (IS_ERR(cur_root) || !cur_root) {
+                       error("failed to read tree: %lld", key.objectid);
+                       goto next;
+               }
+
+               ret = traverse_tree_block(cur_root, cur_root->node);
+               err |= ret;
+
+next:
+               ret = btrfs_next_item(root1, &path);
+               if (ret)
+                       goto out;
        }
-       free(bits);
-       free_chunk_cache_tree(&chunk_cache);
-       free_device_cache_tree(&dev_cache);
-       free_block_group_tree(&block_group_cache);
-       free_device_extent_tree(&dev_extent_cache);
-       free_extent_cache_tree(&seen);
-       free_extent_cache_tree(&pending);
-       free_extent_cache_tree(&reada);
-       free_extent_cache_tree(&nodes);
-       return ret;
-loop:
-       free_corrupt_blocks_tree(root->fs_info->corrupt_blocks);
-       free_extent_cache_tree(&seen);
-       free_extent_cache_tree(&pending);
-       free_extent_cache_tree(&reada);
-       free_extent_cache_tree(&nodes);
-       free_chunk_cache_tree(&chunk_cache);
-       free_block_group_tree(&block_group_cache);
-       free_device_cache_tree(&dev_cache);
-       free_device_extent_tree(&dev_extent_cache);
-       free_extent_record_cache(root->fs_info, &extent_cache);
-       free_root_item_list(&normal_trees);
-       free_root_item_list(&dropping_trees);
-       extent_io_tree_cleanup(&excluded_extents);
-       goto again;
+
+out:
+       btrfs_release_path(&path);
+       return err;
 }
 
 static int btrfs_fsck_reinit_root(struct btrfs_trans_handle *trans,
@@ -8536,24 +11306,20 @@ static int pin_metadata_blocks(struct btrfs_fs_info *fs_info)
 static int reset_block_groups(struct btrfs_fs_info *fs_info)
 {
        struct btrfs_block_group_cache *cache;
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_chunk *chunk;
        struct btrfs_key key;
        int ret;
        u64 start;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
+       btrfs_init_path(&path);
        key.objectid = 0;
        key.type = BTRFS_CHUNK_ITEM_KEY;
        key.offset = 0;
-
-       ret = btrfs_search_slot(NULL, fs_info->chunk_root, &key, path, 0, 0);
+       ret = btrfs_search_slot(NULL, fs_info->chunk_root, &key, &path, 0, 0);
        if (ret < 0) {
-               btrfs_free_path(path);
+               btrfs_release_path(&path);
                return ret;
        }
 
@@ -8568,10 +11334,10 @@ static int reset_block_groups(struct btrfs_fs_info *fs_info)
 
        /* First we need to create the in-memory block groups */
        while (1) {
-               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-                       ret = btrfs_next_leaf(fs_info->chunk_root, path);
+               if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
+                       ret = btrfs_next_leaf(fs_info->chunk_root, &path);
                        if (ret < 0) {
-                               btrfs_free_path(path);
+                               btrfs_release_path(&path);
                                return ret;
                        }
                        if (ret) {
@@ -8579,15 +11345,14 @@ static int reset_block_groups(struct btrfs_fs_info *fs_info)
                                break;
                        }
                }
-               leaf = path->nodes[0];
-               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+               leaf = path.nodes[0];
+               btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.type != BTRFS_CHUNK_ITEM_KEY) {
-                       path->slots[0]++;
+                       path.slots[0]++;
                        continue;
                }
 
-               chunk = btrfs_item_ptr(leaf, path->slots[0],
-                                      struct btrfs_chunk);
+               chunk = btrfs_item_ptr(leaf, path.slots[0], struct btrfs_chunk);
                btrfs_add_block_group(fs_info, 0,
                                      btrfs_chunk_type(leaf, chunk),
                                      key.objectid, key.offset,
@@ -8595,7 +11360,7 @@ static int reset_block_groups(struct btrfs_fs_info *fs_info)
                set_extent_dirty(&fs_info->free_space_cache, key.offset,
                                 key.offset + btrfs_chunk_length(leaf, chunk),
                                 GFP_NOFS);
-               path->slots[0]++;
+               path.slots[0]++;
        }
        start = 0;
        while (1) {
@@ -8606,7 +11371,7 @@ static int reset_block_groups(struct btrfs_fs_info *fs_info)
                start = cache->key.objectid + cache->key.offset;
        }
 
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return 0;
 }
 
@@ -8614,22 +11379,18 @@ static int reset_balance(struct btrfs_trans_handle *trans,
                         struct btrfs_fs_info *fs_info)
 {
        struct btrfs_root *root = fs_info->tree_root;
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        int del_slot, del_nr = 0;
        int ret;
        int found = 0;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
+       btrfs_init_path(&path);
        key.objectid = BTRFS_BALANCE_OBJECTID;
        key.type = BTRFS_BALANCE_ITEM_KEY;
        key.offset = 0;
-
-       ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+       ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
        if (ret) {
                if (ret > 0)
                        ret = 0;
@@ -8639,64 +11400,63 @@ static int reset_balance(struct btrfs_trans_handle *trans,
                        goto out;
        }
 
-       ret = btrfs_del_item(trans, root, path);
+       ret = btrfs_del_item(trans, root, &path);
        if (ret)
                goto out;
-       btrfs_release_path(path);
+       btrfs_release_path(&path);
 
        key.objectid = BTRFS_TREE_RELOC_OBJECTID;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = 0;
-
-       ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+       ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
        if (ret < 0)
                goto out;
        while (1) {
-               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+               if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                        if (!found)
                                break;
 
                        if (del_nr) {
-                               ret = btrfs_del_items(trans, root, path,
+                               ret = btrfs_del_items(trans, root, &path,
                                                      del_slot, del_nr);
                                del_nr = 0;
                                if (ret)
                                        goto out;
                        }
                        key.offset++;
-                       btrfs_release_path(path);
+                       btrfs_release_path(&path);
 
                        found = 0;
-                       ret = btrfs_search_slot(trans, root, &key, path,
+                       ret = btrfs_search_slot(trans, root, &key, &path,
                                                -1, 1);
                        if (ret < 0)
                                goto out;
                        continue;
                }
                found = 1;
-               leaf = path->nodes[0];
-               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+               leaf = path.nodes[0];
+               btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.objectid > BTRFS_TREE_RELOC_OBJECTID)
                        break;
                if (key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
-                       path->slots[0]++;
+                       path.slots[0]++;
                        continue;
                }
                if (!del_nr) {
-                       del_slot = path->slots[0];
+                       del_slot = path.slots[0];
                        del_nr = 1;
                } else {
                        del_nr++;
                }
-               path->slots[0]++;
+               path.slots[0]++;
        }
 
        if (del_nr) {
-               ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
+               ret = btrfs_del_items(trans, root, &path, del_slot, del_nr);
                if (ret)
                        goto out;
        }
-       btrfs_release_path(path);
+       btrfs_release_path(&path);
 
 reinit_data_reloc:
        key.objectid = BTRFS_DATA_RELOC_TREE_OBJECTID;
@@ -8714,7 +11474,7 @@ reinit_data_reloc:
                goto out;
        ret = btrfs_make_root_dir(trans, root, BTRFS_FIRST_FREE_OBJECTID);
 out:
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return ret;
 }
 
@@ -8797,14 +11557,14 @@ static int reinit_extent_tree(struct btrfs_trans_handle *trans,
 
        ret = reset_balance(trans, fs_info);
        if (ret)
-               fprintf(stderr, "error reseting the pending balance\n");
+               fprintf(stderr, "error resetting the pending balance\n");
 
        return ret;
 }
 
 static int recow_extent_buffer(struct btrfs_root *root, struct extent_buffer *eb)
 {
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_trans_handle *trans;
        struct btrfs_key key;
        int ret;
@@ -8821,31 +11581,26 @@ static int recow_extent_buffer(struct btrfs_root *root, struct extent_buffer *eb
                return PTR_ERR(root);
        }
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
        trans = btrfs_start_transaction(root, 1);
-       if (IS_ERR(trans)) {
-               btrfs_free_path(path);
+       if (IS_ERR(trans))
                return PTR_ERR(trans);
-       }
 
-       path->lowest_level = btrfs_header_level(eb);
-       if (path->lowest_level)
+       btrfs_init_path(&path);
+       path.lowest_level = btrfs_header_level(eb);
+       if (path.lowest_level)
                btrfs_node_key_to_cpu(eb, &key, 0);
        else
                btrfs_item_key_to_cpu(eb, &key, 0);
 
-       ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+       ret = btrfs_search_slot(trans, root, &key, &path, 0, 1);
        btrfs_commit_transaction(trans, root);
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return ret;
 }
 
 static int delete_bad_item(struct btrfs_root *root, struct bad_item *bad)
 {
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_trans_handle *trans;
        struct btrfs_key key;
        int ret;
@@ -8863,26 +11618,21 @@ static int delete_bad_item(struct btrfs_root *root, struct bad_item *bad)
                return PTR_ERR(root);
        }
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
        trans = btrfs_start_transaction(root, 1);
-       if (IS_ERR(trans)) {
-               btrfs_free_path(path);
+       if (IS_ERR(trans))
                return PTR_ERR(trans);
-       }
 
-       ret = btrfs_search_slot(trans, root, &bad->key, path, -1, 1);
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(trans, root, &bad->key, &path, -1, 1);
        if (ret) {
                if (ret > 0)
                        ret = 0;
                goto out;
        }
-       ret = btrfs_del_item(trans, root, path);
+       ret = btrfs_del_item(trans, root, &path);
 out:
        btrfs_commit_transaction(trans, root);
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return ret;
 }
 
@@ -8929,7 +11679,7 @@ static int fill_csum_tree_from_one_fs_root(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *csum_root,
                                      struct btrfs_root *cur_root)
 {
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_key key;
        struct extent_buffer *node;
        struct btrfs_file_extent_item *fi;
@@ -8939,30 +11689,25 @@ static int fill_csum_tree_from_one_fs_root(struct btrfs_trans_handle *trans,
        int slot = 0;
        int ret = 0;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
        buf = malloc(cur_root->fs_info->csum_root->sectorsize);
-       if (!buf) {
-               ret = -ENOMEM;
-               goto out;
-       }
+       if (!buf)
+               return -ENOMEM;
 
+       btrfs_init_path(&path);
        key.objectid = 0;
        key.offset = 0;
        key.type = 0;
-
-       ret = btrfs_search_slot(NULL, cur_root, &key, path, 0, 0);
+       ret = btrfs_search_slot(NULL, cur_root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        /* Iterate all regular file extents and fill its csum */
        while (1) {
-               btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+               btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
 
                if (key.type != BTRFS_EXTENT_DATA_KEY)
                        goto next;
-               node = path->nodes[0];
-               slot = path->slots[0];
+               node = path.nodes[0];
+               slot = path.slots[0];
                fi = btrfs_item_ptr(node, slot, struct btrfs_file_extent_item);
                if (btrfs_file_extent_type(node, fi) != BTRFS_FILE_EXTENT_REG)
                        goto next;
@@ -8979,7 +11724,7 @@ next:
                 * TODO: if next leaf is corrupted, jump to nearest next valid
                 * leaf.
                 */
-               ret = btrfs_next_item(cur_root, path);
+               ret = btrfs_next_item(cur_root, &path);
                if (ret < 0)
                        goto out;
                if (ret > 0) {
@@ -8989,7 +11734,7 @@ next:
        }
 
 out:
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        free(buf);
        return ret;
 }
@@ -8998,7 +11743,7 @@ static int fill_csum_tree_from_fs(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *csum_root)
 {
        struct btrfs_fs_info *fs_info = csum_root->fs_info;
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *cur_root;
        struct extent_buffer *node;
@@ -9006,15 +11751,11 @@ static int fill_csum_tree_from_fs(struct btrfs_trans_handle *trans,
        int slot = 0;
        int ret = 0;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
+       btrfs_init_path(&path);
        key.objectid = BTRFS_FS_TREE_OBJECTID;
        key.offset = 0;
        key.type = BTRFS_ROOT_ITEM_KEY;
-
-       ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
+       ret = btrfs_search_slot(NULL, tree_root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        if (ret > 0) {
@@ -9023,8 +11764,8 @@ static int fill_csum_tree_from_fs(struct btrfs_trans_handle *trans,
        }
 
        while (1) {
-               node = path->nodes[0];
-               slot = path->slots[0];
+               node = path.nodes[0];
+               slot = path.slots[0];
                btrfs_item_key_to_cpu(node, &key, slot);
                if (key.objectid > BTRFS_LAST_FREE_OBJECTID)
                        goto out;
@@ -9045,7 +11786,7 @@ static int fill_csum_tree_from_fs(struct btrfs_trans_handle *trans,
                if (ret < 0)
                        goto out;
 next:
-               ret = btrfs_next_item(tree_root, path);
+               ret = btrfs_next_item(tree_root, &path);
                if (ret > 0) {
                        ret = 0;
                        goto out;
@@ -9055,7 +11796,7 @@ next:
        }
 
 out:
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        return ret;
 }
 
@@ -9063,36 +11804,32 @@ static int fill_csum_tree_from_extent(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *csum_root)
 {
        struct btrfs_root *extent_root = csum_root->fs_info->extent_root;
-       struct btrfs_path *path;
+       struct btrfs_path path;
        struct btrfs_extent_item *ei;
        struct extent_buffer *leaf;
        char *buf;
        struct btrfs_key key;
        int ret;
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
+       btrfs_init_path(&path);
        key.objectid = 0;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = 0;
-
-       ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
+       ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
        if (ret < 0) {
-               btrfs_free_path(path);
+               btrfs_release_path(&path);
                return ret;
        }
 
        buf = malloc(csum_root->sectorsize);
        if (!buf) {
-               btrfs_free_path(path);
+               btrfs_release_path(&path);
                return -ENOMEM;
        }
 
        while (1) {
-               if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-                       ret = btrfs_next_leaf(extent_root, path);
+               if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
+                       ret = btrfs_next_leaf(extent_root, &path);
                        if (ret < 0)
                                break;
                        if (ret) {
@@ -9100,19 +11837,19 @@ static int fill_csum_tree_from_extent(struct btrfs_trans_handle *trans,
                                break;
                        }
                }
-               leaf = path->nodes[0];
+               leaf = path.nodes[0];
 
-               btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+               btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.type != BTRFS_EXTENT_ITEM_KEY) {
-                       path->slots[0]++;
+                       path.slots[0]++;
                        continue;
                }
 
-               ei = btrfs_item_ptr(leaf, path->slots[0],
+               ei = btrfs_item_ptr(leaf, path.slots[0],
                                    struct btrfs_extent_item);
                if (!(btrfs_extent_flags(leaf, ei) &
                      BTRFS_EXTENT_FLAG_DATA)) {
-                       path->slots[0]++;
+                       path.slots[0]++;
                        continue;
                }
 
@@ -9120,10 +11857,10 @@ static int fill_csum_tree_from_extent(struct btrfs_trans_handle *trans,
                                    key.offset);
                if (ret)
                        break;
-               path->slots[0]++;
+               path.slots[0]++;
        }
 
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        free(buf);
        return ret;
 }
@@ -9171,7 +11908,7 @@ static int build_roots_info_cache(struct btrfs_fs_info *info)
        int ret = 0;
        struct btrfs_key key;
        struct extent_buffer *leaf;
-       struct btrfs_path *path;
+       struct btrfs_path path;
 
        if (!roots_info_cache) {
                roots_info_cache = malloc(sizeof(*roots_info_cache));
@@ -9180,24 +11917,20 @@ static int build_roots_info_cache(struct btrfs_fs_info *info)
                cache_tree_init(roots_info_cache);
        }
 
-       path = btrfs_alloc_path();
-       if (!path)
-               return -ENOMEM;
-
+       btrfs_init_path(&path);
        key.objectid = 0;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = 0;
-
-       ret = btrfs_search_slot(NULL, info->extent_root, &key, path, 0, 0);
+       ret = btrfs_search_slot(NULL, info->extent_root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
-       leaf = path->nodes[0];
+       leaf = path.nodes[0];
 
        while (1) {
                struct btrfs_key found_key;
                struct btrfs_extent_item *ei;
                struct btrfs_extent_inline_ref *iref;
-               int slot = path->slots[0];
+               int slot = path.slots[0];
                int type;
                u64 flags;
                u64 root_id;
@@ -9206,18 +11939,18 @@ static int build_roots_info_cache(struct btrfs_fs_info *info)
                struct root_item_info *rii;
 
                if (slot >= btrfs_header_nritems(leaf)) {
-                       ret = btrfs_next_leaf(info->extent_root, path);
+                       ret = btrfs_next_leaf(info->extent_root, &path);
                        if (ret < 0) {
                                break;
                        } else if (ret) {
                                ret = 0;
                                break;
                        }
-                       leaf = path->nodes[0];
-                       slot = path->slots[0];
+                       leaf = path.nodes[0];
+                       slot = path.slots[0];
                }
 
-               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+               btrfs_item_key_to_cpu(leaf, &found_key, path.slots[0]);
 
                if (found_key.type != BTRFS_EXTENT_ITEM_KEY &&
                    found_key.type != BTRFS_METADATA_ITEM_KEY)
@@ -9280,11 +12013,11 @@ static int build_roots_info_cache(struct btrfs_fs_info *info)
                        rii->node_count++;
                }
 next:
-               path->slots[0]++;
+               path.slots[0]++;
        }
 
 out:
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
 
        return ret;
 }
@@ -9380,7 +12113,7 @@ static int maybe_repair_root_item(struct btrfs_fs_info *info,
  */
 static int repair_root_items(struct btrfs_fs_info *info)
 {
-       struct btrfs_path *path = NULL;
+       struct btrfs_path path;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct btrfs_trans_handle *trans = NULL;
@@ -9388,16 +12121,12 @@ static int repair_root_items(struct btrfs_fs_info *info)
        int bad_roots = 0;
        int need_trans = 0;
 
+       btrfs_init_path(&path);
+
        ret = build_roots_info_cache(info);
        if (ret)
                goto out;
 
-       path = btrfs_alloc_path();
-       if (!path) {
-               ret = -ENOMEM;
-               goto out;
-       }
-
        key.objectid = BTRFS_FIRST_FREE_OBJECTID;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = 0;
@@ -9416,19 +12145,19 @@ again:
                }
        }
 
-       ret = btrfs_search_slot(trans, info->tree_root, &key, path,
+       ret = btrfs_search_slot(trans, info->tree_root, &key, &path,
                                0, trans ? 1 : 0);
        if (ret < 0)
                goto out;
-       leaf = path->nodes[0];
+       leaf = path.nodes[0];
 
        while (1) {
                struct btrfs_key found_key;
 
-               if (path->slots[0] >= btrfs_header_nritems(leaf)) {
-                       int no_more_keys = find_next_key(path, &key);
+               if (path.slots[0] >= btrfs_header_nritems(leaf)) {
+                       int no_more_keys = find_next_key(&path, &key);
 
-                       btrfs_release_path(path);
+                       btrfs_release_path(&path);
                        if (trans) {
                                ret = btrfs_commit_transaction(trans,
                                                               info->tree_root);
@@ -9442,14 +12171,14 @@ again:
                        goto again;
                }
 
-               btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+               btrfs_item_key_to_cpu(leaf, &found_key, path.slots[0]);
 
                if (found_key.type != BTRFS_ROOT_ITEM_KEY)
                        goto next;
                if (found_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
                        goto next;
 
-               ret = maybe_repair_root_item(info, path, &found_key,
+               ret = maybe_repair_root_item(info, &path, &found_key,
                                             trans ? 0 : 1);
                if (ret < 0)
                        goto out;
@@ -9457,18 +12186,18 @@ again:
                        if (!trans && repair) {
                                need_trans = 1;
                                key = found_key;
-                               btrfs_release_path(path);
+                               btrfs_release_path(&path);
                                goto again;
                        }
                        bad_roots++;
                }
 next:
-               path->slots[0]++;
+               path.slots[0]++;
        }
        ret = 0;
 out:
        free_roots_info_cache();
-       btrfs_free_path(path);
+       btrfs_release_path(&path);
        if (trans)
                btrfs_commit_transaction(trans, info->tree_root);
        if (ret < 0)
@@ -9477,12 +12206,42 @@ out:
        return bad_roots;
 }
 
+static int clear_free_space_cache(struct btrfs_fs_info *fs_info)
+{
+       struct btrfs_trans_handle *trans;
+       struct btrfs_block_group_cache *bg_cache;
+       u64 current = 0;
+       int ret = 0;
+
+       /* Clear all free space cache inodes and its extent data */
+       while (1) {
+               bg_cache = btrfs_lookup_first_block_group(fs_info, current);
+               if (!bg_cache)
+                       break;
+               ret = btrfs_clear_free_space_cache(fs_info, bg_cache);
+               if (ret < 0)
+                       return ret;
+               current = bg_cache->key.objectid + bg_cache->key.offset;
+       }
+
+       /* Don't forget to set cache_generation to -1 */
+       trans = btrfs_start_transaction(fs_info->tree_root, 0);
+       if (IS_ERR(trans)) {
+               error("failed to update super block cache generation");
+               return PTR_ERR(trans);
+       }
+       btrfs_set_super_cache_generation(fs_info->super_copy, (u64)-1);
+       btrfs_commit_transaction(trans, fs_info->tree_root);
+
+       return ret;
+}
+
 const char * const cmd_check_usage[] = {
        "btrfs check [options] <device>",
-       "Check structural inegrity of a filesystem (unmounted).",
-       "Check structural inegrity of an unmounted filesystem. Verify internal",
+       "Check structural integrity of a filesystem (unmounted).",
+       "Check structural integrity of an unmounted filesystem. Verify internal",
        "trees' consistency and item connectivity. In the repair mode try to",
-       "fix the problems found.",
+       "fix the problems found. ",
        "WARNING: the repair mode is considered dangerous",
        "",
        "-s|--super <superblock>     use this superblock copy",
@@ -9491,13 +12250,20 @@ const char * const cmd_check_usage[] = {
        "--readonly                  run in read-only mode (default)",
        "--init-csum-tree            create a new CRC tree",
        "--init-extent-tree          create a new extent tree",
-       "--check-data-csum           verify checkums of data blocks",
-       "-Q|--qgroup-report           print a report on qgroup consistency",
+       "--mode <MODE>               allows choice of memory/IO trade-offs",
+       "                            where MODE is one of:",
+       "                            original - read inodes and extents to memory (requires",
+       "                                       more memory, does less IO)",
+       "                            lowmem   - try to use less memory but read blocks again",
+       "                                       when needed",
+       "--check-data-csum           verify checksums of data blocks",
+       "-Q|--qgroup-report          print a report on qgroup consistency",
        "-E|--subvol-extents <subvolid>",
        "                            print subvolume extents and sharing state",
        "-r|--tree-root <bytenr>     use the given bytenr for the tree root",
        "--chunk-root <bytenr>       use the given bytenr for the chunk tree root",
        "-p|--progress               indicate progress",
+       "--clear-space-cache v1|v2   clear space cache for v1 or v2",
        NULL
 };
 
@@ -9512,17 +12278,21 @@ int cmd_check(int argc, char **argv)
        u64 chunk_root_bytenr = 0;
        char uuidbuf[BTRFS_UUID_UNPARSED_SIZE];
        int ret;
+       int err = 0;
        u64 num;
        int init_csum_tree = 0;
        int readonly = 0;
+       int clear_space_cache = 0;
        int qgroup_report = 0;
-       enum btrfs_open_ctree_flags ctree_flags = OPEN_CTREE_EXCLUSIVE;
+       int qgroups_repaired = 0;
+       unsigned ctree_flags = OPEN_CTREE_EXCLUSIVE;
 
        while(1) {
                int c;
                enum { GETOPT_VAL_REPAIR = 257, GETOPT_VAL_INIT_CSUM,
                        GETOPT_VAL_INIT_EXTENT, GETOPT_VAL_CHECK_CSUM,
-                       GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE };
+                       GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE,
+                       GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE };
                static const struct option long_options[] = {
                        { "super", required_argument, NULL, 's' },
                        { "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
@@ -9540,6 +12310,10 @@ int cmd_check(int argc, char **argv)
                        { "chunk-root", required_argument, NULL,
                                GETOPT_VAL_CHUNK_TREE },
                        { "progress", no_argument, NULL, 'p' },
+                       { "mode", required_argument, NULL,
+                               GETOPT_VAL_MODE },
+                       { "clear-space-cache", required_argument, NULL,
+                               GETOPT_VAL_CLEAR_SPACE_CACHE},
                        { NULL, 0, NULL, 0}
                };
 
@@ -9554,8 +12328,8 @@ int cmd_check(int argc, char **argv)
                        case 's':
                                num = arg_strtou64(optarg);
                                if (num >= BTRFS_SUPER_MIRROR_MAX) {
-                                       fprintf(stderr,
-                                               "ERROR: super mirror should be less than: %d\n",
+                                       error(
+                                       "super mirror should be less than %d",
                                                BTRFS_SUPER_MIRROR_MAX);
                                        exit(1);
                                }
@@ -9604,6 +12378,26 @@ int cmd_check(int argc, char **argv)
                        case GETOPT_VAL_CHECK_CSUM:
                                check_data_csum = 1;
                                break;
+                       case GETOPT_VAL_MODE:
+                               check_mode = parse_check_mode(optarg);
+                               if (check_mode == CHECK_MODE_UNKNOWN) {
+                                       error("unknown mode: %s", optarg);
+                                       exit(1);
+                               }
+                               break;
+                       case GETOPT_VAL_CLEAR_SPACE_CACHE:
+                               if (strcmp(optarg, "v1") == 0) {
+                                       clear_space_cache = 1;
+                               } else if (strcmp(optarg, "v2") == 0) {
+                                       clear_space_cache = 2;
+                                       ctree_flags |= OPEN_CTREE_INVALIDATE_FST;
+                               } else {
+                                       error(
+               "invalid argument to --clear-space-cache, must be v1 or v2");
+                                       exit(1);
+                               }
+                               ctree_flags |= OPEN_CTREE_WRITES;
+                               break;
                }
        }
 
@@ -9617,7 +12411,15 @@ int cmd_check(int argc, char **argv)
 
        /* This check is the only reason for --readonly to exist */
        if (readonly && repair) {
-               fprintf(stderr, "Repair options are not compatible with --readonly\n");
+               error("repair options are not compatible with --readonly");
+               exit(1);
+       }
+
+       /*
+        * Not supported yet
+        */
+       if (repair && check_mode == CHECK_MODE_LOWMEM) {
+               error("low memory mode doesn't support repair yet");
                exit(1);
        }
 
@@ -9625,11 +12427,13 @@ int cmd_check(int argc, char **argv)
        cache_tree_init(&root_cache);
 
        if((ret = check_mounted(argv[optind])) < 0) {
-               fprintf(stderr, "Could not check mount status: %s\n", strerror(-ret));
+               error("could not check mount status: %s", strerror(-ret));
+               err |= !!ret;
                goto err_out;
        } else if(ret) {
-               fprintf(stderr, "%s is currently mounted. Aborting.\n", argv[optind]);
+               error("%s is currently mounted, aborting", argv[optind]);
                ret = -EBUSY;
+               err |= !!ret;
                goto err_out;
        }
 
@@ -9640,27 +12444,64 @@ int cmd_check(int argc, char **argv)
        info = open_ctree_fs_info(argv[optind], bytenr, tree_root_bytenr,
                                  chunk_root_bytenr, ctree_flags);
        if (!info) {
-               fprintf(stderr, "Couldn't open file system\n");
+               error("cannot open file system");
                ret = -EIO;
+               err |= !!ret;
                goto err_out;
        }
 
        global_info = info;
        root = info->fs_root;
+       if (clear_space_cache == 1) {
+               if (btrfs_fs_compat_ro(info,
+                               BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE)) {
+                       error(
+               "free space cache v2 detected, use --clear-space-cache v2");
+                       ret = 1;
+                       goto close_out;
+               }
+               printf("Clearing free space cache\n");
+               ret = clear_free_space_cache(info);
+               if (ret) {
+                       error("failed to clear free space cache");
+                       ret = 1;
+               } else {
+                       printf("Free space cache cleared\n");
+               }
+               goto close_out;
+       } else if (clear_space_cache == 2) {
+               if (!btrfs_fs_compat_ro(info,
+                                       BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE)) {
+                       printf("no free space cache v2 to clear\n");
+                       ret = 0;
+                       goto close_out;
+               }
+               printf("Clear free space cache v2\n");
+               ret = btrfs_clear_free_space_tree(info);
+               if (ret) {
+                       error("failed to clear free space cache v2: %d", ret);
+                       ret = 1;
+               } else {
+                       printf("free space cache v2 cleared\n");
+               }
+               goto close_out;
+       }
 
        /*
         * repair mode will force us to commit transaction which
         * will make us fail to load log tree when mounting.
         */
        if (repair && btrfs_super_log_root(info->super_copy)) {
-               ret = ask_user("repair mode will force to clear out log tree, Are you sure?");
+               ret = ask_user("repair mode will force to clear out log tree, are you sure?");
                if (!ret) {
                        ret = 1;
+                       err |= !!ret;
                        goto close_out;
                }
                ret = zero_log_tree(root);
+               err |= !!ret;
                if (ret) {
-                       fprintf(stderr, "fail to zero log tree\n");
+                       error("failed to zero log tree: %d", ret);
                        goto close_out;
                }
        }
@@ -9670,14 +12511,16 @@ int cmd_check(int argc, char **argv)
                printf("Print quota groups for %s\nUUID: %s\n", argv[optind],
                       uuidbuf);
                ret = qgroup_verify_all(info);
+               err |= !!ret;
                if (ret == 0)
-                       ret = report_qgroups(1);
+                       report_qgroups(1);
                goto close_out;
        }
        if (subvolid) {
                printf("Print extent state for subvolume %llu on %s\nUUID: %s\n",
                       subvolid, argv[optind], uuidbuf);
                ret = print_extent_state(info, subvolid);
+               err |= !!ret;
                goto close_out;
        }
        printf("Checking filesystem on %s\nUUID: %s\n", argv[optind], uuidbuf);
@@ -9685,7 +12528,8 @@ int cmd_check(int argc, char **argv)
        if (!extent_buffer_uptodate(info->tree_root->node) ||
            !extent_buffer_uptodate(info->dev_root->node) ||
            !extent_buffer_uptodate(info->chunk_root->node)) {
-               fprintf(stderr, "Critical roots corrupted, unable to fsck the FS\n");
+               error("critical roots corrupted, unable to check the filesystem");
+               err |= !!ret;
                ret = -EIO;
                goto close_out;
        }
@@ -9695,31 +12539,36 @@ int cmd_check(int argc, char **argv)
 
                trans = btrfs_start_transaction(info->extent_root, 0);
                if (IS_ERR(trans)) {
-                       fprintf(stderr, "Error starting transaction\n");
+                       error("error starting transaction");
                        ret = PTR_ERR(trans);
+                       err |= !!ret;
                        goto close_out;
                }
 
                if (init_extent_tree) {
                        printf("Creating a new extent tree\n");
                        ret = reinit_extent_tree(trans, info);
+                       err |= !!ret;
                        if (ret)
                                goto close_out;
                }
 
                if (init_csum_tree) {
-                       fprintf(stderr, "Reinit crc root\n");
+                       printf("Reinitialize checksum tree\n");
                        ret = btrfs_fsck_reinit_root(trans, info->csum_root, 0);
                        if (ret) {
-                               fprintf(stderr, "crc root initialization failed\n");
+                               error("checksum tree initialization failed: %d",
+                                               ret);
                                ret = -EIO;
+                               err |= !!ret;
                                goto close_out;
                        }
 
                        ret = fill_csum_tree(trans, info->csum_root,
                                             init_extent_tree);
+                       err |= !!ret;
                        if (ret) {
-                               fprintf(stderr, "crc refilling failed\n");
+                               error("checksum tree refilling failed: %d", ret);
                                return -EIO;
                        }
                }
@@ -9728,27 +12577,36 @@ int cmd_check(int argc, char **argv)
                 * extent entries for all of the items it finds.
                 */
                ret = btrfs_commit_transaction(trans, info->extent_root);
+               err |= !!ret;
                if (ret)
                        goto close_out;
        }
        if (!extent_buffer_uptodate(info->extent_root->node)) {
-               fprintf(stderr, "Critical roots corrupted, unable to fsck the FS\n");
+               error("critical: extent_root, unable to check the filesystem");
                ret = -EIO;
+               err |= !!ret;
                goto close_out;
        }
        if (!extent_buffer_uptodate(info->csum_root->node)) {
-               fprintf(stderr, "Checksum root corrupted, rerun with --init-csum-tree option\n");
+               error("critical: csum_root, unable to check the filesystem");
                ret = -EIO;
+               err |= !!ret;
                goto close_out;
        }
 
        if (!ctx.progress_enabled)
                fprintf(stderr, "checking extents\n");
-       ret = check_chunks_and_extents(root);
+       if (check_mode == CHECK_MODE_LOWMEM)
+               ret = check_chunks_and_extents_v2(root);
+       else
+               ret = check_chunks_and_extents(root);
+       err |= !!ret;
        if (ret)
-               fprintf(stderr, "Errors found in extent allocation tree or chunk allocation\n");
+               error(
+               "errors found in extent allocation tree or chunk allocation");
 
        ret = repair_root_items(info);
+       err |= !!ret;
        if (ret < 0)
                goto close_out;
        if (repair) {
@@ -9761,6 +12619,7 @@ int cmd_check(int argc, char **argv)
                fprintf(stderr,
                        "Please run a filesystem check with the option --repair to fix them.\n");
                ret = 1;
+               err |= !!ret;
                goto close_out;
        }
 
@@ -9771,6 +12630,7 @@ int cmd_check(int argc, char **argv)
                        fprintf(stderr, "checking free space cache\n");
        }
        ret = check_space_cache(root);
+       err |= !!ret;
        if (ret)
                goto out;
 
@@ -9784,19 +12644,28 @@ int cmd_check(int argc, char **argv)
                                     BTRFS_FEATURE_INCOMPAT_NO_HOLES);
        if (!ctx.progress_enabled)
                fprintf(stderr, "checking fs roots\n");
-       ret = check_fs_roots(root, &root_cache);
+       if (check_mode == CHECK_MODE_LOWMEM)
+               ret = check_fs_roots_v2(root->fs_info);
+       else
+               ret = check_fs_roots(root, &root_cache);
+       err |= !!ret;
        if (ret)
                goto out;
 
        fprintf(stderr, "checking csums\n");
        ret = check_csums(root);
+       err |= !!ret;
        if (ret)
                goto out;
 
        fprintf(stderr, "checking root refs\n");
-       ret = check_root_refs(root, &root_cache);
-       if (ret)
-               goto out;
+       /* For low memory mode, check_fs_roots_v2 handles root refs */
+       if (check_mode != CHECK_MODE_LOWMEM) {
+               ret = check_root_refs(root, &root_cache);
+               err |= !!ret;
+               if (ret)
+                       goto out;
+       }
 
        while (repair && !list_empty(&root->fs_info->recow_ebs)) {
                struct extent_buffer *eb;
@@ -9805,6 +12674,7 @@ int cmd_check(int argc, char **argv)
                                      struct extent_buffer, recow);
                list_del_init(&eb->recow);
                ret = recow_extent_buffer(root, eb);
+               err |= !!ret;
                if (ret)
                        break;
        }
@@ -9814,29 +12684,33 @@ int cmd_check(int argc, char **argv)
 
                bad = list_first_entry(&delete_items, struct bad_item, list);
                list_del_init(&bad->list);
-               if (repair)
+               if (repair) {
                        ret = delete_bad_item(root, bad);
+                       err |= !!ret;
+               }
                free(bad);
        }
 
        if (info->quota_enabled) {
-               int err;
                fprintf(stderr, "checking quota groups\n");
-               err = qgroup_verify_all(info);
+               ret = qgroup_verify_all(info);
+               err |= !!ret;
+               if (ret)
+                       goto out;
+               report_qgroups(0);
+               ret = repair_qgroups(info, &qgroups_repaired);
+               err |= !!ret;
                if (err)
                        goto out;
+               ret = 0;
        }
 
        if (!list_empty(&root->fs_info->recow_ebs)) {
-               fprintf(stderr, "Transid errors in file system\n");
+               error("transid errors in file system");
                ret = 1;
+               err |= !!ret;
        }
 out:
-       /* Don't override original ret */
-       if (ret)
-               report_qgroups(0);
-       else
-               ret = report_qgroups(0);
        if (found_old_backref) { /*
                 * there was a disk format change when mixed
                 * backref was in testing tree. The old format
@@ -9846,7 +12720,7 @@ out:
                       "The old format is not supported! *"
                       "\n * Please mount the FS in readonly mode, "
                       "backup data and re-format the FS. *\n\n");
-               ret = 1;
+               err |= 1;
        }
        printf("found %llu bytes used err is %d\n",
               (unsigned long long)bytes_used, ret);
@@ -9863,6 +12737,7 @@ out:
                (unsigned long long)data_bytes_allocated,
                (unsigned long long)data_bytes_referenced);
 
+       free_qgroup_counts();
        free_root_recs_tree(&root_cache);
 close_out:
        close_ctree(root);
@@ -9870,5 +12745,5 @@ err_out:
        if (ctx.progress_enabled)
                task_deinit(ctx.info);
 
-       return ret;
+       return err;
 }