Btrfs: Properly find the root for snapshotted blocks during chunk relocation

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 33ab165..f4b4677 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1459,6 +1459,8 @@ int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root
                      *item);
 int btrfs_find_last_root(struct btrfs_root *root, u64 objectid, struct
                         btrfs_root_item *item, struct btrfs_key *key);
+int btrfs_search_root(struct btrfs_root *root, u64 search_start,
+                     u64 *found_objectid);
 int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid,
                          struct btrfs_root *latest_root);
 /* dir-item.c */

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index c0e67bd..8e69b5a 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2422,6 +2422,85 @@ truncate_racing:
 }
 
 /*
+ * The back references tell us which tree holds a ref on a block,
+ * but it is possible for the tree root field in the reference to
+ * reflect the original root before a snapshot was made.  In this
+ * case we should search through all the children of a given root
+ * to find potential holders of references on a block.
+ *
+ * Instead, we do something a little less fancy and just search
+ * all the roots for a given key/block combination.
+ */
+static int find_root_for_ref(struct btrfs_root *root,
+                            struct btrfs_path *path,
+                            struct btrfs_key *key0,
+                            int level,
+                            int file_key,
+                            struct btrfs_root **found_root,
+                            u64 bytenr)
+{
+       struct btrfs_key root_location;
+       struct btrfs_root *cur_root = *found_root;
+       struct btrfs_file_extent_item *file_extent;
+       u64 root_search_start = BTRFS_FS_TREE_OBJECTID;
+       u64 found_bytenr;
+       int ret;
+       int i;
+
+       root_location.offset = (u64)-1;
+       root_location.type = BTRFS_ROOT_ITEM_KEY;
+       path->lowest_level = level;
+       path->reada = 0;
+       while(1) {
+               ret = btrfs_search_slot(NULL, cur_root, key0, path, 0, 0);
+               found_bytenr = 0;
+               if (ret == 0 && file_key) {
+                       struct extent_buffer *leaf = path->nodes[0];
+                       file_extent = btrfs_item_ptr(leaf, path->slots[0],
+                                            struct btrfs_file_extent_item);
+                       if (btrfs_file_extent_type(leaf, file_extent) ==
+                           BTRFS_FILE_EXTENT_REG) {
+                               found_bytenr =
+                                       btrfs_file_extent_disk_bytenr(leaf,
+                                                              file_extent);
+                      }
+               } else if (ret == 0) {
+                       if (path->nodes[level])
+                               found_bytenr = path->nodes[level]->start;
+               }
+
+               for (i = level; i < BTRFS_MAX_LEVEL; i++) {
+                       if (!path->nodes[i])
+                               break;
+                       free_extent_buffer(path->nodes[i]);
+                       path->nodes[i] = NULL;
+               }
+               btrfs_release_path(cur_root, path);
+
+               if (found_bytenr == bytenr) {
+                       *found_root = cur_root;
+                       ret = 0;
+                       goto out;
+               }
+               ret = btrfs_search_root(root->fs_info->tree_root,
+                                       root_search_start, &root_search_start);
+               if (ret)
+                       break;
+
+               root_location.objectid = root_search_start;
+               cur_root = btrfs_read_fs_root_no_name(root->fs_info,
+                                                     &root_location);
+               if (!cur_root) {
+                       ret = 1;
+                       break;
+               }
+       }
+out:
+       path->lowest_level = 0;
+       return ret;
+}
+
+/*
  * note, this releases the path
  */
 static int noinline relocate_one_reference(struct btrfs_root *extent_root,
@@ -2430,13 +2509,15 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
 {
        struct inode *inode;
        struct btrfs_root *found_root;
-       struct btrfs_key *root_location;
+       struct btrfs_key root_location;
+       struct btrfs_key found_key;
        struct btrfs_extent_ref *ref;
        u64 ref_root;
        u64 ref_gen;
        u64 ref_objectid;
        u64 ref_offset;
        int ret;
+       int level;
 
        ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
                             struct btrfs_extent_ref);
@@ -2446,20 +2527,30 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
        ref_offset = btrfs_ref_offset(path->nodes[0], ref);
        btrfs_release_path(extent_root, path);
 
-       root_location = kmalloc(sizeof(*root_location), GFP_NOFS);
-       root_location->objectid = ref_root;
+       root_location.objectid = ref_root;
        if (ref_gen == 0)
-               root_location->offset = 0;
+               root_location.offset = 0;
        else
-               root_location->offset = (u64)-1;
-       root_location->type = BTRFS_ROOT_ITEM_KEY;
+               root_location.offset = (u64)-1;
+       root_location.type = BTRFS_ROOT_ITEM_KEY;
 
        found_root = btrfs_read_fs_root_no_name(extent_root->fs_info,
-                                               root_location);
+                                               &root_location);
        BUG_ON(!found_root);
-       kfree(root_location);
 
        if (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID) {
+               found_key.objectid = ref_objectid;
+               found_key.type = BTRFS_EXTENT_DATA_KEY;
+               found_key.offset = ref_offset;
+               level = 0;
+
+               ret = find_root_for_ref(extent_root, path, &found_key,
+                                       level, 1, &found_root,
+                                       extent_key->objectid);
+
+               if (ret)
+                       goto out;
+
                mutex_unlock(&extent_root->fs_info->fs_mutex);
                inode = btrfs_iget_locked(extent_root->fs_info->sb,
                                          ref_objectid, found_root);
@@ -2485,12 +2576,9 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
                mutex_lock(&extent_root->fs_info->fs_mutex);
        } else {
                struct btrfs_trans_handle *trans;
-               struct btrfs_key found_key;
                struct extent_buffer *eb;
-               int level;
                int i;
 
-               trans = btrfs_start_transaction(found_root, 1);
                eb = read_tree_block(found_root, extent_key->objectid,
                                     extent_key->offset);
                level = btrfs_header_level(eb);
@@ -2502,6 +2590,15 @@ static int noinline relocate_one_reference(struct btrfs_root *extent_root,
 
                free_extent_buffer(eb);
 
+               ret = find_root_for_ref(extent_root, path, &found_key,
+                                       level, 0, &found_root,
+                                       extent_key->objectid);
+
+               if (ret)
+                       goto out;
+
+               trans = btrfs_start_transaction(found_root, 1);
+
                path->lowest_level = level;
                path->reada = 2;
                ret = btrfs_search_slot(trans, found_root, &found_key, path,
@@ -2578,6 +2675,7 @@ static int noinline relocate_one_extent(struct btrfs_root *extent_root,
                        }
                        if (ret < 0)
                                goto out;
+                       leaf = path->nodes[0];
                }
 
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 08f19ec..8bf21ba 100644 (file)
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -21,6 +21,51 @@
 #include "disk-io.h"
 #include "print-tree.h"
 
+/*
+ * returns 0 on finding something, 1 if no more roots are there
+ * and < 0 on error
+ */
+int btrfs_search_root(struct btrfs_root *root, u64 search_start,
+                     u64 *found_objectid)
+{
+       struct btrfs_path *path;
+       struct btrfs_key search_key;
+       int ret;
+
+       root = root->fs_info->tree_root;
+       search_key.objectid = search_start;
+       search_key.type = (u8)-1;
+       search_key.offset = (u64)-1;
+
+       path = btrfs_alloc_path();
+       BUG_ON(!path);
+again:
+       ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
+       if (ret < 0)
+               goto out;
+       if (ret == 0) {
+               ret = 1;
+               goto out;
+       }
+       if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+               ret = btrfs_next_leaf(root, path);
+               if (ret)
+                       goto out;
+       }
+       btrfs_item_key_to_cpu(path->nodes[0], &search_key, path->slots[0]);
+       if (search_key.type != BTRFS_ROOT_ITEM_KEY) {
+               search_key.offset++;
+               btrfs_release_path(root, path);
+               goto again;
+       }
+       ret = 0;
+       *found_objectid = search_key.objectid;
+
+out:
+       btrfs_free_path(path);
+       return ret;
+}
+
 int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
                        struct btrfs_root_item *item, struct btrfs_key *key)
 {
@@ -55,7 +100,6 @@ int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
        memcpy(key, &found_key, sizeof(found_key));
        ret = 0;
 out:
-       btrfs_release_path(root, path);
        btrfs_free_path(path);
        return ret;
 }