From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Tejun Heo <tj@kernel.org>,
linux-block@vger.kernel.org, Ming Lei <ming.lei@redhat.com>
Subject: [PATCH 1/4] block: factor out a blk_try_enter_queue helper
Date: Mon, 20 Sep 2021 13:24:02 +0200 [thread overview]
Message-ID: <20210920112405.1299667-2-hch@lst.de> (raw)
In-Reply-To: <20210920112405.1299667-1-hch@lst.de>
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>
---
block/blk-core.c | 60 ++++++++++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 28 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 5454db2fa263b..4c078681f39b8 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -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)
--
2.30.2
next prev parent reply other threads:[~2021-09-20 11:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 11:24 tear down file system I/O in del_gendisk Christoph Hellwig
2021-09-20 11:24 ` Christoph Hellwig [this message]
2021-09-21 3:17 ` [PATCH 1/4] block: factor out a blk_try_enter_queue helper Bart Van Assche
2021-09-20 11:24 ` [PATCH 2/4] block: split bio_queue_enter from blk_queue_enter Christoph Hellwig
2021-09-21 3:25 ` Bart Van Assche
2021-09-20 11:24 ` [PATCH 3/4] block: drain file system I/O on del_gendisk Christoph Hellwig
2021-09-20 11:24 ` [PATCH 4/4] block: keep q_usage_counter in atomic mode after del_gendisk Christoph Hellwig
2021-09-21 3:29 ` Bart Van Assche
2021-09-21 9:07 ` Christoph Hellwig
2021-09-21 3:38 ` tear down file system I/O in del_gendisk Bart Van Assche
2021-09-21 9:08 ` Christoph Hellwig
2021-09-21 14:24 ` Bart Van Assche
2021-09-21 22:33 ` Bart Van Assche
2021-09-22 17:22 tear down file system I/O in del_gendisk v2 Christoph Hellwig
2021-09-22 17:22 ` [PATCH 1/4] block: factor out a blk_try_enter_queue helper Christoph Hellwig
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