linux-kernel - [PATCH v4 3/6] block: add blk_mq_is_queue

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Date:   Wed, 3 Feb 2021 18:53:55 +0300
From:   Sergei Shtepa <sergei.shtepa@...am.com>
To:     <Damien.LeMoal@....com>, <snitzer@...hat.com>, <hare@...e.de>,
        <ming.lei@...hat.com>, <agk@...hat.com>, <corbet@....net>,
        <axboe@...nel.dk>, <jack@...e.cz>, <johannes.thumshirn@....com>,
        <gregkh@...uxfoundation.org>, <koct9i@...il.com>, <steve@....org>,
        <dm-devel@...hat.com>, <linux-block@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <sergei.shtepa@...am.com>, <pavgel.tide@...am.com>
Subject: [PATCH v4 3/6] block: add blk_mq_is_queue_frozen()

blk_mq_is_queue_frozen() allow to assert that the queue is frozen.

Signed-off-by: Sergei Shtepa <sergei.shtepa@...am.com>
---
 block/blk-mq.c         | 13 +++++++++++++
 include/linux/blk-mq.h |  1 +
 2 files changed, 14 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f285a9123a8b..924ec26fae5f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -161,6 +161,19 @@ int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
 
+
+bool blk_mq_is_queue_frozen(struct request_queue *q)
+{
+	bool ret;
+
+	mutex_lock(&q->mq_freeze_lock);
+	ret = percpu_ref_is_dying(&q->q_usage_counter) && percpu_ref_is_zero(&q->q_usage_counter);
+	mutex_unlock(&q->mq_freeze_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(blk_mq_is_queue_frozen);
+
 /*
  * Guarantee no request is in use, so we can change any data structure of
  * the queue afterward.
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index d705b174d346..9d1e8c4e922e 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -525,6 +525,7 @@ void blk_freeze_queue_start(struct request_queue *q);
 void blk_mq_freeze_queue_wait(struct request_queue *q);
 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
 				     unsigned long timeout);
+bool blk_mq_is_queue_frozen(struct request_queue *q);
 
 int blk_mq_map_queues(struct blk_mq_queue_map *qmap);
 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
-- 
2.20.1