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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: Christoph Hellwig <hch@lst.de>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20210929071241.934472-3-hch@lst.de
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2021-09-29 09:12:38 +02:00 committed by Jens Axboe
parent cc9c884dd7
commit 1f14a09890
1 changed files with 32 additions and 28 deletions
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60
block/blk-core.c
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@ -416,6 +416,30 @@ void blk_cleanup_queue(struct request_queue *q)
} }
EXPORT_SYMBOL(blk_cleanup_queue); 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 * blk_queue_enter() - try to increase q->q_usage_counter
* @q: request queue pointer * @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; const bool pm = flags & BLK_MQ_REQ_PM;
while (true) { while (!blk_try_enter_queue(q, pm)) {
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;
if (flags & BLK_MQ_REQ_NOWAIT) if (flags & BLK_MQ_REQ_NOWAIT)
return -EBUSY; return -EBUSY;
/* /*
* read pair of barrier in blk_freeze_queue_start(), * read pair of barrier in blk_freeze_queue_start(), we need to
* we need to order reading __PERCPU_REF_DEAD flag of * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
* .q_usage_counter and reading .mq_freeze_depth or * reading .mq_freeze_depth or queue dying flag, otherwise the
* queue dying flag, otherwise the following wait may * following wait may never return if the two reads are
* never return if the two reads are reordered. * reordered.
*/ */
smp_rmb(); smp_rmb();
wait_event(q->mq_freeze_wq, wait_event(q->mq_freeze_wq,
(!q->mq_freeze_depth && (!q->mq_freeze_depth &&
blk_pm_resume_queue(pm, q)) || 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)) if (blk_queue_dying(q))
return -ENODEV; return -ENODEV;
} }
return 0;
} }
static inline int bio_queue_enter(struct bio *bio) static inline int bio_queue_enter(struct bio *bio)