When the btrfs_read_fs_root() function is searching a ROOT_ITEM with location key offset other than -1, it currently fails via BUG_ON.
The offset can have other value than -1, though. This can happen for example if a subvolume is renamed:
$ btrfs subvolume create X && sync Create subvolume './X' $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: X$ location key (270 ROOT_ITEM 18446744073709551615) type DIR transid 283 data_len 0 name_len 1 name: X $ mv X Y && sync $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: Y$ location key (270 ROOT_ITEM 0) type DIR transid 285 data_len 0 name_len 1 name: Y
As can be seen the offset changed from -1ULL to 0.
Do not fail in this case.
Signed-off-by: Marek Behún marek.behun@nic.cz Cc: David Sterba dsterba@suse.com Cc: Qu Wenruo wqu@suse.com Cc: Tom Rini trini@konsulko.com --- fs/btrfs/disk-io.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index b332ecb796..c6fdec95c1 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -732,8 +732,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info, return fs_info->chunk_root; if (location->objectid == BTRFS_CSUM_TREE_OBJECTID) return fs_info->csum_root; - BUG_ON(location->objectid == BTRFS_TREE_RELOC_OBJECTID || - location->offset != (u64)-1); + BUG_ON(location->objectid == BTRFS_TREE_RELOC_OBJECTID);
node = rb_search(&fs_info->fs_root_tree, (void *)&objectid, btrfs_fs_roots_compare_objectids, NULL);