[PATCH 2/8] blk-mq: skip non-mq queues in blk_mq_quiesce_queue

[Christoph Hellwig]

For submit_bio based queues there is no (S)RCU critical section during
I/O submission and thus nothing to wait for in blk_mq_wait_quiesce_done,
so skip doing any synchronization.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 block/blk-mq.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 33292c01875d5..df967c8af9fee 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -280,7 +280,9 @@ EXPORT_SYMBOL_GPL(blk_mq_wait_quiesce_done);
 void blk_mq_quiesce_queue(struct request_queue *q)
 {
 	blk_mq_quiesce_queue_nowait(q);
-	blk_mq_wait_quiesce_done(q);
+	/* nothing to wait for non-mq queues */
+	if (queue_is_mq(q))
+		blk_mq_wait_quiesce_done(q);
 }
 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
 
-- 
2.30.2