Commit e70feb8b authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

blk-mq: support concurrent queue quiesce/unquiesce 

blk_mq_quiesce_queue() has been used a bit wide now, so far we don't support
concurrent/nested quiesce. One biggest issue is that unquiesce can happen
unexpectedly in case that quiesce/unquiesce are run concurrently from
more than one context.

This patch introduces q->mq_quiesce_depth to deal concurrent quiesce,
and we only unquiesce queue when it is the last/outer-most one of all
contexts.

Several kernel panic issue has been reported[1][2][3] when running stress
quiesce test. And this patch has been verified in these reports.

[1] https://lore.kernel.org/linux-block/9b21c797-e505-3821-4f5b-df7bf9380328@huawei.com/T/#m1fc52431fad7f33b1ffc3f12c4450e4238540787
[2] https://lore.kernel.org/linux-block/9b21c797-e505-3821-4f5b-df7bf9380328@huawei.com/T/#m10ad90afeb9c8cc318334190a7c24c8b5c5e0722
[3] https://listman.redhat.com/archives/dm-devel/2021-September/msg00189.html



Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211014081710.1871747-7-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 1d35d519

block/blk-mq.c

+19 −3
Original line number Diff line number Diff line
@@ -241,7 +241,12 @@ EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue); 
 */

void blk_mq_quiesce_queue_nowait(struct request_queue *q)

{

	unsigned long flags;



	spin_lock_irqsave(&q->queue_lock, flags);

	if (!q->quiesce_depth++)

		blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);

	spin_unlock_irqrestore(&q->queue_lock, flags);

}

EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
@@ -282,9 +287,20 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue); 
 */

void blk_mq_unquiesce_queue(struct request_queue *q)

{

	unsigned long flags;

	bool run_queue = false;



	spin_lock_irqsave(&q->queue_lock, flags);

	if (WARN_ON_ONCE(q->quiesce_depth <= 0)) {

		;

	} else if (!--q->quiesce_depth) {

		blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);

		run_queue = true;

	}

	spin_unlock_irqrestore(&q->queue_lock, flags);



	/* dispatch requests which are inserted during quiescing */

	if (run_queue)

		blk_mq_run_hw_queues(q, true);

}

EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);

include/linux/blkdev.h

+2 −0
Original line number Diff line number Diff line
@@ -315,6 +315,8 @@ struct request_queue { 
	 */

	struct mutex		mq_freeze_lock;



	int			quiesce_depth;



	struct blk_mq_tag_set	*tag_set;

	struct list_head	tag_set_list;

	struct bio_set		bio_split;