[PATCH v2 6/8] blk-mq: don't stop queue for quiescing

[Ming Lei <ming.lei@redhat.com>]

Queue can be started by other blk-mq APIs and can be used in
different cases, this limits uses of blk_mq_quiesce_queue()
if it is based on stopping queue, and make its usage very
difficult, especially users have to use the stop queue APIs
carefully for avoiding to break blk_mq_quiesce_queue().

We have applied the QUIESCED flag for draining and blocking
dispatch, so it isn't necessary to stop queue any more.

After stopping queue is removed, blk_mq_quiesce_queue() can
be used safely and easily, then users won't worry about queue
restarting during quiescing at all.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 032045841856..84cce67caee3 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -168,8 +168,6 @@ void blk_mq_quiesce_queue(struct request_queue *q)
 	unsigned int i;
 	bool rcu = false;
 
-	__blk_mq_stop_hw_queues(q, true);
-
 	spin_lock_irq(q->queue_lock);
 	queue_flag_set(QUEUE_FLAG_QUIESCED, q);
 	spin_unlock_irq(q->queue_lock);
@@ -198,7 +196,12 @@ void blk_mq_unquiesce_queue(struct request_queue *q)
 	queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
 	spin_unlock_irq(q->queue_lock);
 
-	blk_mq_start_stopped_hw_queues(q, true);
+	/*
+	 * During quiescing, requests can be inserted
+	 * to scheduler's queue or sw queue, so we run
+	 * queues for dispatching these requests.
+	 */
+	blk_mq_start_hw_queues(q);
 }
 EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
 
-- 
2.9.4