dm mpath: return DM_MAPIO_DELAY_REQUEUE if QUEUE_IO or PG_INIT_REQUIRED

Avoid using DM_MAPIO_REQUEUE unless absolutely necessary because it
results in dm-rq.c:dm_mq_queue_rq() returning BLK_STS_RESOURCE to
blk-mq -- doing so should only ever be done if the underlying queue is
out of resources.  So switch to returning DM_MAPIO_DELAY_REQUEUE from
multipath_clone_and_map() if either MPATHF_QUEUE_IO or
MPATHF_PG_INIT_REQUIRED are set.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-mpath.c

@@ -517,9 +517,8 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 		return DM_MAPIO_KILL;
 	} else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 		   test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
-		if (pg_init_all_paths(m))
-			return DM_MAPIO_DELAY_REQUEUE;
-		return DM_MAPIO_REQUEUE;
+		pg_init_all_paths(m);
+		return DM_MAPIO_DELAY_REQUEUE;
 	}
 
 	mpio->pgpath = pgpath;