Btrfs: fix backref walking race with tree deletions

When a subvolume is removed, we remove the root item from the root tree,
while the tree blocks and backrefs remain for a while. When backref walking
comes across one of those orphan tree blocks, it can find a backref for a
no longer existing root. This is all good, we only must tolerate
__resolve_indirect_ref returning an error and continue with the good refs
found.

Reported-by: Alex Lyakas <alex.btrfs@zadarastorage.com>
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 1 insertions, 4 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 04edf69be875..bd605c87adfd 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -352,11 +352,8 @@ static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
                 err = __resolve_indirect_ref(fs_info, search_commit_root,
                                              time_seq, ref, parents,
                                              extent_item_pos);
-                if (err) {
-                        if (ret == 0)
-                                ret = err;
+                if (err)
                         continue;
-                }
 
                 /* we put the first parent into the ref at hand */
                 ULIST_ITER_INIT(&uiter);