dm raid1: fix immutable biovec related BUG when retrying read bio

When restoring bi_end_io, increase bi_remaining before retrying the bio
to avoid BUG_ON(atomic_read(&bio->bi_remaining) <= 0) in bio_endio().

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-raid1.c

@@ -1244,6 +1244,9 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
 
 			dm_bio_restore(bd, bio);
 			bio_record->details.bi_bdev = NULL;
+
+			atomic_inc(&bio->bi_remaining);
+
 			queue_bio(ms, bio, rw);
 			return DM_ENDIO_INCOMPLETE;
 		}