md: fix bi_status reporting in md_end_clone_io

md_end_clone_io() may overwrite error status in orig_bio->bi_status with
BLK_STS_OK. This could happen when orig_bio has BIO_CHAIN (split by
md_submit_bio => bio_split_to_limits, for example). As a result, upper
layer may miss error reported from md (or the device) and consider the
failed IO was successful.

Fix this by only update orig_bio->bi_status when current bio reports
error and orig_bio is BLK_STS_OK. This is the same behavior as
__bio_chain_endio().

Fixes: 10764815 ("md: add io accounting for raid0 and raid5")
Cc: stable@vger.kernel.org # v5.14+
Reported-by: Bhanu Victor DiCara <00bvd0+linux@gmail.com>
Closes: https://lore.kernel.org/regressions/5727380.DvuYhMxLoT@bvd0/Signed-off-by: Song Liu <song@kernel.org>
Tested-by: Xiao Ni <xni@redhat.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>

drivers/md/md.c

@@ -8666,7 +8666,8 @@ static void md_end_clone_io(struct bio *bio)
 	struct bio *orig_bio = md_io_clone->orig_bio;
 	struct mddev *mddev = md_io_clone->mddev;
 
-	orig_bio->bi_status = bio->bi_status;
+	if (bio->bi_status && !orig_bio->bi_status)
+		orig_bio->bi_status = bio->bi_status;
 
 	if (md_io_clone->start_time)
 		bio_end_io_acct(orig_bio, md_io_clone->start_time);