btrfs: do not warn if we can't find the reloc root when looking up backref

The backref code is looking for a reloc_root that corresponds to the
given fs root.  However any number of things could have gone wrong while
initializing that reloc_root, like ENOMEM while trying to allocate the
root itself, or EIO while trying to write the root item.  This would
result in no corresponding reloc_root being in the reloc root cache, and
thus would return NULL when we do the find_reloc_root() call.

Because of this we do not want to WARN_ON().  This presumably was meant
to catch developer errors, cases where we messed up adding the reloc
root.  However we can easily hit this case with error injection, and
thus should not do a WARN_ON().

CC: stable@vger.kernel.org # 5.10+
Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 701124c3e0b140060316682c31faee40d395de05..f47c1528eb9a69aeba5f2cd0740333a05aa9238d 100644 (file)
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -2623,7 +2623,7 @@ static int handle_direct_tree_backref(struct btrfs_backref_cache *cache,
                /* Only reloc backref cache cares about a specific root */
                if (cache->is_reloc) {
                        root = find_reloc_root(cache->fs_info, cur->bytenr);
                /* Only reloc backref cache cares about a specific root */
                if (cache->is_reloc) {
                        root = find_reloc_root(cache->fs_info, cur->bytenr);

-                       if (WARN_ON(!root))
+                       if (!root)

                                return -ENOENT;
                        cur->root = root;
                } else {
                                return -ENOENT;
                        cur->root = root;
                } else {