[PATCH v4 3/6] block: add blk_mq_is_queue_frozen()

From: Sergei Shtepa <sergei.shtepa@veeam.com>
To: <Damien.LeMoal@wdc.com>, <snitzer@redhat.com>, <hare@suse.de>,
	<ming.lei@redhat.com>, <agk@redhat.com>, <corbet@lwn.net>,
	<axboe@kernel.dk>, <jack@suse.cz>, <johannes.thumshirn@wdc.com>,
	<gregkh@linuxfoundation.org>, <koct9i@gmail.com>, <steve@sk2.org>,
	<dm-devel@redhat.com>, <linux-block@vger.kernel.org>,
	<linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: <sergei.shtepa@veeam.com>, <pavgel.tide@veeam.com>
Subject: [PATCH v4 3/6] block: add blk_mq_is_queue_frozen()
Date: Wed, 3 Feb 2021 18:53:55 +0300	[thread overview]
Message-ID: <1612367638-3794-4-git-send-email-sergei.shtepa@veeam.com> (raw)
In-Reply-To: <1612367638-3794-1-git-send-email-sergei.shtepa@veeam.com>

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

Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.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

