btrfs-progs: check: introduce low memory mode
[platform/upstream/btrfs-progs.git] / cmds-check.c
index 6a748ac..c40e5da 100644 (file)
@@ -70,6 +70,7 @@ static LIST_HEAD(delete_items);
 static int no_holes = 0;
 static int init_extent_tree = 0;
 static int check_data_csum = 0;
+static int low_memory = 0;
 static struct btrfs_fs_info *global_info;
 static struct task_ctx ctx = { 0 };
 static struct cache_tree *roots_info_cache = NULL;
@@ -434,6 +435,23 @@ 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;
@@ -1953,8 +1971,14 @@ 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;
@@ -1967,12 +1991,20 @@ 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) {
@@ -2003,10 +2035,19 @@ 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,
@@ -3619,6 +3660,7 @@ 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
@@ -3640,6 +3682,7 @@ 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,
@@ -3689,7 +3732,7 @@ 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)
@@ -8514,172 +8557,1625 @@ loop:
        goto again;
 }
 
-static int btrfs_fsck_reinit_root(struct btrfs_trans_handle *trans,
-                          struct btrfs_root *root, int overwrite)
+/*
+ * 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 check_tree_block_ref(struct btrfs_root *root,
+                               struct extent_buffer *eb, u64 bytenr,
+                               int level, u64 owner)
 {
-       struct extent_buffer *c;
-       struct extent_buffer *old = root->node;
-       int level;
+       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_disk_key disk_key = {0,0,0};
 
-       level = 0;
+       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;
 
-       if (overwrite) {
-               c = old;
-               extent_buffer_get(c);
-               goto init;
+       /* 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;
        }
-       c = btrfs_alloc_free_block(trans, root,
-                                  root->nodesize,
-                                  root->root_key.objectid,
-                                  &disk_key, level, 0, 0);
-       if (IS_ERR(c)) {
-               c = old;
-               extent_buffer_get(c);
-               overwrite = 1;
+       ret = btrfs_previous_extent_item(extent_root, &path, bytenr);
+       if (ret) {
+               err |= BACKREF_MISSING;
+               goto out;
        }
-init:
-       memset_extent_buffer(c, 0, 0, sizeof(struct btrfs_header));
-       btrfs_set_header_level(c, level);
-       btrfs_set_header_bytenr(c, c->start);
-       btrfs_set_header_generation(c, trans->transid);
-       btrfs_set_header_backref_rev(c, BTRFS_MIXED_BACKREF_REV);
-       btrfs_set_header_owner(c, root->root_key.objectid);
 
-       write_extent_buffer(c, root->fs_info->fsid,
-                           btrfs_header_fsid(), BTRFS_FSID_SIZE);
+       leaf = path.nodes[0];
+       slot = path.slots[0];
+       btrfs_item_key_to_cpu(leaf, &key, slot);
 
-       write_extent_buffer(c, root->fs_info->chunk_tree_uuid,
-                           btrfs_header_chunk_tree_uuid(c),
-                           BTRFS_UUID_SIZE);
+       ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
+
+       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;
+
+               info = (struct btrfs_tree_block_info *)(ei + 1);
+               skinny_level = btrfs_tree_block_level(leaf, info);
+               iref = (struct btrfs_extent_inline_ref *)(info + 1);
+       }
+
+       if (eb) {
+               u64 header_gen;
+               u64 extent_gen;
+
+               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;
+               }
+       }
 
-       btrfs_mark_buffer_dirty(c);
        /*
-        * this case can happen in the following case:
-        *
-        * 1.overwrite previous root.
-        *
-        * 2.reinit reloc data root, this is because we skip pin
-        * down reloc data tree before which means we can allocate
-        * same block bytenr here.
+        * Iterate the extent/metadata item to find the exact backref
         */
-       if (old->start == c->start) {
-               btrfs_set_root_generation(&root->root_item,
-                                         trans->transid);
-               root->root_item.level = btrfs_header_level(root->node);
-               ret = btrfs_update_root(trans, root->fs_info->tree_root,
-                                       &root->root_key, &root->root_item);
-               if (ret) {
-                       free_extent_buffer(c);
-                       return ret;
+       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 (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);
        }
-       free_extent_buffer(old);
-       root->node = c;
-       add_root_to_dirty_list(root);
-       return 0;
+
+       /*
+        * 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)
+                       found_ref = 1;
+       }
+       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 pin_down_tree_blocks(struct btrfs_fs_info *fs_info,
-                               struct extent_buffer *eb, int tree_root)
+/*
+ * 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 extent_buffer *tmp;
-       struct btrfs_root_item *ri;
-       struct btrfs_key key;
-       u64 bytenr;
-       u32 nodesize;
-       int level = btrfs_header_level(eb);
-       int nritems;
+       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_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;
-       int i;
 
-       /*
-        * If we have pinned this block before, don't pin it again.
-        * This can not only avoid forever loop with broken filesystem
-        * but also give us some speedups.
-        */
-       if (test_range_bit(&fs_info->pinned_extents, eb->start,
-                          eb->start + eb->len - 1, EXTENT_DIRTY, 0))
+       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;
 
-       btrfs_pin_extent(fs_info, eb->start, eb->len);
+       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 {
+               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);
 
-       nodesize = btrfs_super_nodesize(fs_info->super_copy);
-       nritems = btrfs_header_nritems(eb);
-       for (i = 0; i < nritems; i++) {
-               if (level == 0) {
-                       btrfs_item_key_to_cpu(eb, &key, i);
-                       if (key.type != BTRFS_ROOT_ITEM_KEY)
-                               continue;
-                       /* Skip the extent root and reloc roots */
-                       if (key.objectid == BTRFS_EXTENT_TREE_OBJECTID ||
-                           key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
-                           key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
-                               continue;
-                       ri = btrfs_item_ptr(eb, i, struct btrfs_root_item);
-                       bytenr = btrfs_disk_root_bytenr(eb, ri);
+       /* 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);
 
-                       /*
-                        * If at any point we start needing the real root we
-                        * will have to build a stump root for the root we are
-                        * in, but for now this doesn't actually use the root so
-                        * just pass in extent_root.
-                        */
-                       tmp = read_tree_block(fs_info->extent_root, bytenr,
-                                             nodesize, 0);
-                       if (!extent_buffer_uptodate(tmp)) {
-                               fprintf(stderr, "Error reading root block\n");
-                               return -EIO;
-                       }
-                       ret = pin_down_tree_blocks(fs_info, tmp, 0);
-                       free_extent_buffer(tmp);
-                       if (ret)
-                               return ret;
-               } else {
-                       bytenr = btrfs_node_blockptr(eb, i);
+       ret = btrfs_search_slot(NULL, extent_root, &dbref_key, &path, 0, 0);
+       if (ret) {
+               err |= BACKREF_MISSING;
+               goto error;
+       }
 
-                       /* If we aren't the tree root don't read the block */
-                       if (level == 1 && !tree_root) {
-                               btrfs_pin_extent(fs_info, bytenr, nodesize);
-                               continue;
-                       }
+       leaf = path.nodes[0];
+       slot = path.slots[0];
+       ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 
-                       tmp = read_tree_block(fs_info->extent_root, bytenr,
-                                             nodesize, 0);
-                       if (!extent_buffer_uptodate(tmp)) {
-                               fprintf(stderr, "Error reading tree block\n");
-                               return -EIO;
-                       }
-                       ret = pin_down_tree_blocks(fs_info, tmp, tree_root);
-                       free_extent_buffer(tmp);
-                       if (ret)
-                               return ret;
+       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;
+       }
+
+       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;
+       }
+
+       /* 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);
        }
 
-       return 0;
-}
+       /* Didn't found inlined data backref, try EXTENT_DATA_REF_KEY */
+       if (!found_dbackref) {
+               btrfs_release_path(&path);
 
-static int pin_metadata_blocks(struct btrfs_fs_info *fs_info)
-{
-       int ret;
+               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 = pin_down_tree_blocks(fs_info, fs_info->chunk_root->node, 0);
-       if (ret)
-               return ret;
+               ret = btrfs_search_slot(NULL, root->fs_info->extent_root,
+                                       &dbref_key, &path, 0, 0);
+               if (!ret)
+                       found_dbackref = 1;
+       }
 
-       return pin_down_tree_blocks(fs_info, fs_info->tree_root->node, 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;
 }
 
-static int reset_block_groups(struct btrfs_fs_info *fs_info)
+/*
+ * 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)
 {
-       struct btrfs_block_group_cache *cache;
-       struct btrfs_path *path;
-       struct extent_buffer *leaf;
-       struct btrfs_chunk *chunk;
+       struct extent_buffer *eb;
+       struct btrfs_path path;
        struct btrfs_key key;
-       int ret;
+       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;
+
+       /* 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 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;
+       }
+
+       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 release_out;
+       }
+
+       /* Get transid for later read_tree_block() check */
+       transid = btrfs_extent_generation(path.nodes[0], ei);
+
+       /* Get backref level as one source */
+       if (key.type == BTRFS_METADATA_ITEM_KEY) {
+               backref_level = key.offset;
+       } else {
+               struct btrfs_tree_block_info *info;
+
+               info = (struct btrfs_tree_block_info *)(ei + 1);
+               backref_level = btrfs_tree_block_level(path.nodes[0], info);
+       }
+       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);
+
+       if (header_level != backref_level)
+               return -EIO;
+       return header_level;
+
+release_out:
+       btrfs_release_path(&path);
+       return ret;
+}
+
+/*
+ * 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_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;
+
+       /* 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 (level)
+               btrfs_node_key_to_cpu(eb, &key, 0);
+       else
+               btrfs_item_key_to_cpu(eb, &key, 0);
+
+       free_extent_buffer(eb);
+
+       btrfs_init_path(&path);
+       /* Search with the first key, to ensure we can reach it */
+       ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+       if (ret) {
+               err |= REFERENCER_MISSING;
+               goto release_out;
+       }
+
+       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;
+}
+
+/*
+ * 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_buffer *eb;
+       u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       u32 nr;
+       int found_parent = 0;
+       int i;
+
+       eb = read_tree_block_fs_info(fs_info, parent, nodesize, 0);
+       if (!extent_buffer_uptodate(eb))
+               goto out;
+
+       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;
+               }
+       }
+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;
+}
+
+/*
+ * 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;
+
+       if (!len) {
+               key.objectid = bytenr;
+               key.type = BTRFS_EXTENT_ITEM_KEY;
+               key.offset = (u64)-1;
+
+               btrfs_init_path(&path);
+               ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
+               if (ret < 0)
+                       goto out;
+               ret = btrfs_previous_extent_item(extent_root, &path, bytenr);
+               if (ret)
+                       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;
+       btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
+       key.offset = (u64)-1;
+       btrfs_init_path(&path);
+
+       root = btrfs_read_fs_root(fs_info, &key);
+       if (IS_ERR(root))
+               goto out;
+
+       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;
+
+       ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+       if (ret < 0)
+               goto out;
+
+       /*
+        * 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];
+
+               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);
+               /*
+                * 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 (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++;
+
+               ret = btrfs_next_item(root, &path);
+               if (ret)
+                       break;
+       }
+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;
+}
+
+/*
+ * 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;
+
+       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;
+               }
+       }
+
+out:
+       free_extent_buffer(eb);
+       if (!found_parent) {
+               error("shared extent %llu referencer lost (parent: %llu)",
+                       bytenr, parent);
+               return REFERENCER_MISSING;
+       }
+       return 0;
+}
+
+/*
+ * 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)
+{
+       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;
+
+       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(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 {
+               /* New METADATA_ITEM */
+               level = key.offset;
+       }
+       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 if a dev extent item is referred correctly by its chunk
+ */
+static int check_dev_extent_item(struct btrfs_fs_info *fs_info,
+                                struct extent_buffer *eb, int slot)
+{
+       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 i;
+       int found_chunk = 0;
+       int ret;
+
+       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;
+               }
+       }
+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;
+}
+
+/*
+ * 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;
+
+       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;
+       }
+
+       /* 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 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 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;
+
+       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);
+
+       chunk_key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+       chunk_key.type = BTRFS_CHUNK_ITEM_KEY;
+       chunk_key.offset = bg_key.objectid;
+
+       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;
+               }
+       }
+       btrfs_release_path(&path);
+
+       /* Search from the block group bytenr */
+       extent_key.objectid = bg_key.objectid;
+       extent_key.type = 0;
+       extent_key.offset = 0;
+
+       btrfs_init_path(&path);
+       ret = btrfs_search_slot(NULL, extent_root, &extent_key, &path, 0, 0);
+       if (ret < 0)
+               goto out;
+
+       /* 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;
+
+               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;
+       }
+
+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 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 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;
+
+       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;
+       }
+
+       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;
+       }
+       if (profile && (profile & (profile - 1))) {
+               error("chunk[%llu %llu) multiple profiles detected: %llx",
+                       chunk_key.offset, chunk_end, profile);
+               err |= UNKNOWN_TYPE;
+       }
+
+       bg_key.objectid = chunk_key.offset;
+       bg_key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+       bg_key.offset = length;
+
+       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;
+               }
+       }
+
+       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);
+
+               ret = btrfs_search_slot(NULL, dev_root, &devext_key, &path,
+                                       0, 0);
+               if (ret)
+                       goto not_match_dev;
+
+               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;
+}
+
+/*
+ * 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)
+{
+       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;
+
+next:
+       btrfs_item_key_to_cpu(eb, &key, slot);
+       type = btrfs_key_type(&key);
+
+       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;
+}
+
+/*
+ * 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 btrfs_root *extent_root = root->fs_info->extent_root;
+       struct btrfs_key key;
+       struct btrfs_path path;
+       struct extent_buffer *leaf;
+       int slot;
+       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;
+
+       btrfs_init_path(&path);
+       key.objectid = btrfs_header_bytenr(eb);
+       key.type = BTRFS_METADATA_ITEM_KEY;
+       key.offset = (u64)-1;
+
+       /*
+        * 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;
+
+       ret = btrfs_previous_extent_item(extent_root, &path,
+                                        btrfs_header_bytenr(eb));
+       if (ret)
+               goto need_check;
+
+       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 (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);
+       }
+
+       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);
+
+               /*
+                * 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;
+               }
+
+               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;
+       int level;
+       u64 nr;
+       int i;
+       int err = 0;
+       int ret;
+
+       /*
+        * Skip shared fs/subvolume tree block, in that case they will
+        * be checked by referencer with lowest rootid
+        */
+       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;
+       }
+
+       nr = btrfs_header_nritems(node);
+       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);
+
+               /*
+                * 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);
+       }
+
+       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;
+       }
+
+       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;
+
+               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;
+       }
+
+out:
+       btrfs_release_path(&path);
+       return err;
+}
+
+static int btrfs_fsck_reinit_root(struct btrfs_trans_handle *trans,
+                          struct btrfs_root *root, int overwrite)
+{
+       struct extent_buffer *c;
+       struct extent_buffer *old = root->node;
+       int level;
+       int ret;
+       struct btrfs_disk_key disk_key = {0,0,0};
+
+       level = 0;
+
+       if (overwrite) {
+               c = old;
+               extent_buffer_get(c);
+               goto init;
+       }
+       c = btrfs_alloc_free_block(trans, root,
+                                  root->nodesize,
+                                  root->root_key.objectid,
+                                  &disk_key, level, 0, 0);
+       if (IS_ERR(c)) {
+               c = old;
+               extent_buffer_get(c);
+               overwrite = 1;
+       }
+init:
+       memset_extent_buffer(c, 0, 0, sizeof(struct btrfs_header));
+       btrfs_set_header_level(c, level);
+       btrfs_set_header_bytenr(c, c->start);
+       btrfs_set_header_generation(c, trans->transid);
+       btrfs_set_header_backref_rev(c, BTRFS_MIXED_BACKREF_REV);
+       btrfs_set_header_owner(c, root->root_key.objectid);
+
+       write_extent_buffer(c, root->fs_info->fsid,
+                           btrfs_header_fsid(), BTRFS_FSID_SIZE);
+
+       write_extent_buffer(c, root->fs_info->chunk_tree_uuid,
+                           btrfs_header_chunk_tree_uuid(c),
+                           BTRFS_UUID_SIZE);
+
+       btrfs_mark_buffer_dirty(c);
+       /*
+        * this case can happen in the following case:
+        *
+        * 1.overwrite previous root.
+        *
+        * 2.reinit reloc data root, this is because we skip pin
+        * down reloc data tree before which means we can allocate
+        * same block bytenr here.
+        */
+       if (old->start == c->start) {
+               btrfs_set_root_generation(&root->root_item,
+                                         trans->transid);
+               root->root_item.level = btrfs_header_level(root->node);
+               ret = btrfs_update_root(trans, root->fs_info->tree_root,
+                                       &root->root_key, &root->root_item);
+               if (ret) {
+                       free_extent_buffer(c);
+                       return ret;
+               }
+       }
+       free_extent_buffer(old);
+       root->node = c;
+       add_root_to_dirty_list(root);
+       return 0;
+}
+
+static int pin_down_tree_blocks(struct btrfs_fs_info *fs_info,
+                               struct extent_buffer *eb, int tree_root)
+{
+       struct extent_buffer *tmp;
+       struct btrfs_root_item *ri;
+       struct btrfs_key key;
+       u64 bytenr;
+       u32 nodesize;
+       int level = btrfs_header_level(eb);
+       int nritems;
+       int ret;
+       int i;
+
+       /*
+        * If we have pinned this block before, don't pin it again.
+        * This can not only avoid forever loop with broken filesystem
+        * but also give us some speedups.
+        */
+       if (test_range_bit(&fs_info->pinned_extents, eb->start,
+                          eb->start + eb->len - 1, EXTENT_DIRTY, 0))
+               return 0;
+
+       btrfs_pin_extent(fs_info, eb->start, eb->len);
+
+       nodesize = btrfs_super_nodesize(fs_info->super_copy);
+       nritems = btrfs_header_nritems(eb);
+       for (i = 0; i < nritems; i++) {
+               if (level == 0) {
+                       btrfs_item_key_to_cpu(eb, &key, i);
+                       if (key.type != BTRFS_ROOT_ITEM_KEY)
+                               continue;
+                       /* Skip the extent root and reloc roots */
+                       if (key.objectid == BTRFS_EXTENT_TREE_OBJECTID ||
+                           key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
+                           key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
+                               continue;
+                       ri = btrfs_item_ptr(eb, i, struct btrfs_root_item);
+                       bytenr = btrfs_disk_root_bytenr(eb, ri);
+
+                       /*
+                        * If at any point we start needing the real root we
+                        * will have to build a stump root for the root we are
+                        * in, but for now this doesn't actually use the root so
+                        * just pass in extent_root.
+                        */
+                       tmp = read_tree_block(fs_info->extent_root, bytenr,
+                                             nodesize, 0);
+                       if (!extent_buffer_uptodate(tmp)) {
+                               fprintf(stderr, "Error reading root block\n");
+                               return -EIO;
+                       }
+                       ret = pin_down_tree_blocks(fs_info, tmp, 0);
+                       free_extent_buffer(tmp);
+                       if (ret)
+                               return ret;
+               } else {
+                       bytenr = btrfs_node_blockptr(eb, i);
+
+                       /* If we aren't the tree root don't read the block */
+                       if (level == 1 && !tree_root) {
+                               btrfs_pin_extent(fs_info, bytenr, nodesize);
+                               continue;
+                       }
+
+                       tmp = read_tree_block(fs_info->extent_root, bytenr,
+                                             nodesize, 0);
+                       if (!extent_buffer_uptodate(tmp)) {
+                               fprintf(stderr, "Error reading tree block\n");
+                               return -EIO;
+                       }
+                       ret = pin_down_tree_blocks(fs_info, tmp, tree_root);
+                       free_extent_buffer(tmp);
+                       if (ret)
+                               return ret;
+               }
+       }
+
+       return 0;
+}
+
+static int pin_metadata_blocks(struct btrfs_fs_info *fs_info)
+{
+       int ret;
+
+       ret = pin_down_tree_blocks(fs_info, fs_info->chunk_root->node, 0);
+       if (ret)
+               return ret;
+
+       return pin_down_tree_blocks(fs_info, fs_info->tree_root->node, 1);
+}
+
+static int reset_block_groups(struct btrfs_fs_info *fs_info)
+{
+       struct btrfs_block_group_cache *cache;
+       struct btrfs_path *path;
+       struct extent_buffer *leaf;
+       struct btrfs_chunk *chunk;
+       struct btrfs_key key;
+       int ret;
        u64 start;
 
        path = btrfs_alloc_path();
@@ -9630,6 +11126,7 @@ 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",
+       "--low-memory                check in low memory usage mode(experimental)",
        "--check-data-csum           verify checksums of data blocks",
        "-Q|--qgroup-report           print a report on qgroup consistency",
        "-E|--subvol-extents <subvolid>",
@@ -9655,13 +11152,15 @@ int cmd_check(int argc, char **argv)
        int init_csum_tree = 0;
        int readonly = 0;
        int qgroup_report = 0;
+       int qgroups_repaired = 0;
        enum btrfs_open_ctree_flags 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_LOW_MEMORY };
                static const struct option long_options[] = {
                        { "super", required_argument, NULL, 's' },
                        { "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
@@ -9679,6 +11178,8 @@ int cmd_check(int argc, char **argv)
                        { "chunk-root", required_argument, NULL,
                                GETOPT_VAL_CHUNK_TREE },
                        { "progress", no_argument, NULL, 'p' },
+                       { "low-memory", no_argument, NULL,
+                               GETOPT_VAL_LOW_MEMORY },
                        { NULL, 0, NULL, 0}
                };
 
@@ -9743,6 +11244,9 @@ int cmd_check(int argc, char **argv)
                        case GETOPT_VAL_CHECK_CSUM:
                                check_data_csum = 1;
                                break;
+                       case GETOPT_VAL_LOW_MEMORY:
+                               low_memory = 1;
+                               break;
                }
        }
 
@@ -9760,6 +11264,14 @@ int cmd_check(int argc, char **argv)
                exit(1);
        }
 
+       /*
+        * Not supported yet
+        */
+       if (repair && low_memory) {
+               error("Low memory mode doesn't support repair yet");
+               exit(1);
+       }
+
        radix_tree_init();
        cache_tree_init(&root_cache);
 
@@ -9810,7 +11322,7 @@ int cmd_check(int argc, char **argv)
                       uuidbuf);
                ret = qgroup_verify_all(info);
                if (ret == 0)
-                       ret = report_qgroups(1);
+                       report_qgroups(1);
                goto close_out;
        }
        if (subvolid) {
@@ -9883,7 +11395,10 @@ int cmd_check(int argc, char **argv)
 
        if (!ctx.progress_enabled)
                fprintf(stderr, "checking extents\n");
-       ret = check_chunks_and_extents(root);
+       if (low_memory)
+               ret = check_chunks_and_extents_v2(root);
+       else
+               ret = check_chunks_and_extents(root);
        if (ret)
                fprintf(stderr, "Errors found in extent allocation tree or chunk allocation\n");
 
@@ -9964,6 +11479,10 @@ int cmd_check(int argc, char **argv)
                err = qgroup_verify_all(info);
                if (err)
                        goto out;
+               report_qgroups(0);
+               err = repair_qgroups(info, &qgroups_repaired);
+               if (err)
+                       goto out;
        }
 
        if (!list_empty(&root->fs_info->recow_ebs)) {
@@ -9972,10 +11491,9 @@ int cmd_check(int argc, char **argv)
        }
 out:
        /* Don't override original ret */
-       if (ret)
-               report_qgroups(0);
-       else
-               ret = report_qgroups(0);
+       if (!ret && qgroups_repaired)
+               ret = qgroups_repaired;
+
        if (found_old_backref) { /*
                 * there was a disk format change when mixed
                 * backref was in testing tree. The old format