btrfs: remove BUG_ON() at btrfs_destroy_delayed_refs()

At btrfs_destroy_delayed_refs() it's unexpected to not find the block
group to which a delayed reference's extent belongs to, so we have this
BUG_ON(), not just because it's highly unexpected but also because we
don't know what to do there.

Since we are in the transaction abort path, there's nothing we can do
other than proceed and cleanup all used resources we can. So remove
the BUG_ON() and deal with a missing block group by logging an error
message and continuing to cleanup all we can related to the current
delayed ref head and moving to other delayed refs.

Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 24 insertions, 13 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index bcf6e53bc2a7..47598e525ea5 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4571,19 +4571,30 @@ static void btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
 			struct btrfs_block_group *cache;
 
 			cache = btrfs_lookup_block_group(fs_info, head->bytenr);
-			BUG_ON(!cache);
-
-			spin_lock(&cache->space_info->lock);
-			spin_lock(&cache->lock);
-			cache->pinned += head->num_bytes;
-			btrfs_space_info_update_bytes_pinned(fs_info,
-				cache->space_info, head->num_bytes);
-			cache->reserved -= head->num_bytes;
-			cache->space_info->bytes_reserved -= head->num_bytes;
-			spin_unlock(&cache->lock);
-			spin_unlock(&cache->space_info->lock);
-
-			btrfs_put_block_group(cache);
+			if (WARN_ON_ONCE(cache == NULL)) {
+				/*
+				 * Unexpected and there's nothing we can do here
+				 * because we are in a transaction abort path,
+				 * so any errors can only be ignored or reported
+				 * while attempting to cleanup all resources.
+				 */
+				btrfs_err(fs_info,
+"block group for delayed ref at %llu was not found while destroying ref head",
+					  head->bytenr);
+			} else {
+				spin_lock(&cache->space_info->lock);
+				spin_lock(&cache->lock);
+				cache->pinned += head->num_bytes;
+				btrfs_space_info_update_bytes_pinned(fs_info,
+								     cache->space_info,
+								     head->num_bytes);
+				cache->reserved -= head->num_bytes;
+				cache->space_info->bytes_reserved -= head->num_bytes;
+				spin_unlock(&cache->lock);
+				spin_unlock(&cache->space_info->lock);
+
+				btrfs_put_block_group(cache);
+			}
 
 			btrfs_error_unpin_extent_range(fs_info, head->bytenr,
 				head->bytenr + head->num_bytes - 1);