[PATCH btrfs-progs] btrfs-progs: do not fail when offset of a ROOT_ITEM is not -1

[Marek Behún]

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 at nic.cz>
Cc: David Sterba <dsterba at suse.com>
Cc: Qu Wenruo <wqu at suse.com>
Cc: Tom Rini <trini at konsulko.com>
---
 kernel-shared/disk-io.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel-shared/disk-io.c b/kernel-shared/disk-io.c
index 6f584986..ba8ffd8b 100644
--- a/kernel-shared/disk-io.c
+++ b/kernel-shared/disk-io.c
@@ -752,8 +752,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
 		return fs_info->free_space_root ? fs_info->free_space_root :
 						ERR_PTR(-ENOENT);
 
-	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);
-- 
2.26.2