dm: do not return early from dm_io_complete if BLK_STS_AGAIN without polling

Commit 5291984004 ("dm: fix bio polling to handle possibile
BLK_STS_AGAIN") inadvertently introduced an early return from
dm_io_complete() without first queueing the bio to DM if BLK_STS_AGAIN
occurs and bio-polling is _not_ being used.

Fix this by only returning early from dm_io_complete() if the bio has
first been properly queued to DM. Otherwise, the bio will never finish
via bio_endio.

Fixes: 5291984004 ("dm: fix bio polling to handle possibile BLK_STS_AGAIN")
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

drivers/md/dm.c

@@ -939,9 +939,11 @@ static void dm_io_complete(struct dm_io *io)
 			if (io_error == BLK_STS_AGAIN) {
 				/* io_uring doesn't handle BLK_STS_AGAIN (yet) */
 				queue_io(md, bio);
+				return;
 			}
 		}
-		return;
+		if (io_error == BLK_STS_DM_REQUEUE)
+			return;
 	}
 
 	if (bio_is_flush_with_data(bio)) {