[PATCH AUTOSEL 6.4 14/15] btrfs: abort transaction at update_ref_for_cow() when ref count is zero

[Sasha Levin]

From: Filipe Manana <fdmanana@xxxxxxxx>

[ Upstream commit eced687e224eb3cc5a501cf53ad9291337c8dbc5 ]

At update_ref_for_cow() we are calling btrfs_handle_fs_error() if we find
that the extent buffer has an unexpected ref count of zero, however we can
simply use btrfs_abort_transaction(), which achieves the same purposes: to
turn the fs to error state, abort the current transaction and turn the fs
to RO mode as well. Besides that, btrfs_abort_transaction() also prints a
stack trace which makes it more useful.

Also, as this is a very unexpected situation, indicating a serious
corruption/inconsistency, tag the if branch as 'unlikely', set the error
code to -EUCLEAN instead of -EROFS, and log an explicit message.

Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/btrfs/ctree.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 2ff2961b11830..0ba4d1e6a94ec 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -417,9 +417,13 @@ static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
 					       &refs, &flags);
 		if (ret)
 			return ret;
-		if (refs == 0) {
-			ret = -EROFS;
-			btrfs_handle_fs_error(fs_info, ret, NULL);
+		if (unlikely(refs == 0)) {
+			btrfs_crit(fs_info,
+		"found 0 references for tree block at bytenr %llu level %d root %llu",
+				   buf->start, btrfs_header_level(buf),
+				   btrfs_root_id(root));
+			ret = -EUCLEAN;
+			btrfs_abort_transaction(trans, ret);
 			return ret;
 		}
 	} else {
-- 
2.39.2