Btrfs: fix nocow when deleting the item

btrfs_previous_item() just search the b+ tree, do not COW the nodes or leaves,
if we modify the result of it, the meta-data will be broken. fix it.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f8e2943101a1..c37433d3cd82 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -999,7 +999,7 @@ static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
         key.objectid = device->devid;
         key.offset = start;
         key.type = BTRFS_DEV_EXTENT_KEY;
-
+again:
         ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
         if (ret > 0) {
                 ret = btrfs_previous_item(root, path, key.objectid,
@@ -1012,6 +1012,9 @@ static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
                                         struct btrfs_dev_extent);
                 BUG_ON(found_key.offset > start || found_key.offset +
                        btrfs_dev_extent_length(leaf, extent) < start);
+                key = found_key;
+                btrfs_release_path(path);
+                goto again;
         } else if (ret == 0) {
                 leaf = path->nodes[0];
                 extent = btrfs_item_ptr(leaf, path->slots[0],