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Commit cddd5d17 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

blk-mq: blk_mq_freeze_queue() should allow nesting 



While converting to percpu_ref for freezing, add703fd ("blk-mq:
use percpu_ref for mq usage count") incorrectly made
blk_mq_freeze_queue() misbehave when freezing is nested due to
percpu_ref_kill() being invoked on an already killed ref.

Fix it by making blk_mq_freeze_queue() kill and kick the queue only
for the outermost freeze attempt.  All the nested ones can simply wait
for the ref to reach zero.

While at it, remove unnecessary @wake initialization from
blk_mq_unfreeze_queue().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarMing Lei <ming.lei@canonical.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent a68aafa5

block/blk-mq.c

+8 −4
Original line number Diff line number Diff line
@@ -112,18 +112,22 @@ static void blk_mq_usage_counter_release(struct percpu_ref *ref) 
 */

void blk_mq_freeze_queue(struct request_queue *q)

{

	bool freeze;



	spin_lock_irq(q->queue_lock);

	q->mq_freeze_depth++;

	freeze = !q->mq_freeze_depth++;

	spin_unlock_irq(q->queue_lock);



	if (freeze) {

		percpu_ref_kill(&q->mq_usage_counter);

		blk_mq_run_queues(q, false);

	}

	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));

}



static void blk_mq_unfreeze_queue(struct request_queue *q)

{

	bool wake = false;

	bool wake;



	spin_lock_irq(q->queue_lock);

	wake = !--q->mq_freeze_depth;