Commit 1f14a098 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: factor out a blk_try_enter_queue helper 



Factor out the code to try to get q_usage_counter without blocking into
a separate helper.  Both to improve code readability and to prepare for
splitting bio_queue_enter from blk_queue_enter.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Tested-by: default avatarDarrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20210929071241.934472-3-hch@lst.de


Tested-by: default avatarYi Zhang <yi.zhang@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent cc9c884d

block/blk-core.c

+32 −28
Original line number Diff line number Diff line
@@ -416,6 +416,30 @@ void blk_cleanup_queue(struct request_queue *q) 
}

EXPORT_SYMBOL(blk_cleanup_queue);



static bool blk_try_enter_queue(struct request_queue *q, bool pm)

{

	rcu_read_lock();

	if (!percpu_ref_tryget_live(&q->q_usage_counter))

		goto fail;



	/*

	 * The code that increments the pm_only counter must ensure that the

	 * counter is globally visible before the queue is unfrozen.

	 */

	if (blk_queue_pm_only(q) &&

	    (!pm || queue_rpm_status(q) == RPM_SUSPENDED))

		goto fail_put;



	rcu_read_unlock();

	return true;



fail_put:

	percpu_ref_put(&q->q_usage_counter);

fail:

	rcu_read_unlock();

	return false;

}



/**

 * blk_queue_enter() - try to increase q->q_usage_counter

 * @q: request queue pointer
@@ -425,40 +449,18 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) 
{

	const bool pm = flags & BLK_MQ_REQ_PM;



	while (true) {

		bool success = false;



		rcu_read_lock();

		if (percpu_ref_tryget_live(&q->q_usage_counter)) {

			/*

			 * The code that increments the pm_only counter is

			 * responsible for ensuring that that counter is

			 * globally visible before the queue is unfrozen.

			 */

			if ((pm && queue_rpm_status(q) != RPM_SUSPENDED) ||

			    !blk_queue_pm_only(q)) {

				success = true;

			} else {

				percpu_ref_put(&q->q_usage_counter);

			}

		}

		rcu_read_unlock();



		if (success)

			return 0;



	while (!blk_try_enter_queue(q, pm)) {

		if (flags & BLK_MQ_REQ_NOWAIT)

			return -EBUSY;



		/*

		 * read pair of barrier in blk_freeze_queue_start(),

		 * we need to order reading __PERCPU_REF_DEAD flag of

		 * .q_usage_counter and reading .mq_freeze_depth or

		 * queue dying flag, otherwise the following wait may

		 * never return if the two reads are reordered.

		 * read pair of barrier in blk_freeze_queue_start(), we need to

		 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and

		 * reading .mq_freeze_depth or queue dying flag, otherwise the

		 * following wait may never return if the two reads are

		 * reordered.

		 */

		smp_rmb();



		wait_event(q->mq_freeze_wq,

			   (!q->mq_freeze_depth &&

			    blk_pm_resume_queue(pm, q)) ||
@@ -466,6 +468,8 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) 
		if (blk_queue_dying(q))

			return -ENODEV;

	}



	return 0;

}



static inline int bio_queue_enter(struct bio *bio)