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From:   Sergei Shtepa <sergei.shtepa@veeam.com>
To:     Christoph Hellwig <hch@infradead.org>,
        Mike Snitzer <snitzer@redhat.com>,
        Alasdair Kergon <agk@redhat.com>,
        Hannes Reinecke <hare@suse.de>, Jens Axboe <axboe@kernel.dk>,
        <dm-devel@redhat.com>, <linux-block@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-api@vger.kernel.org>
CC:     <sergei.shtepa@veeam.com>, <pavel.tide@veeam.com>
Subject: [PATCH v7 1/3] block: add blk_mq_is_queue_frozen()
Date:   Fri, 12 Mar 2021 18:44:53 +0300
Message-ID: <1615563895-28565-2-git-send-email-sergei.shtepa@veeam.com>
In-Reply-To: <1615563895-28565-1-git-send-email-sergei.shtepa@veeam.com>
References: <1615563895-28565-1-git-send-email-sergei.shtepa@veeam.com>
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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 d4d7c1caa439..2f188a865024 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 frozen;
+
+	mutex_lock(&q->mq_freeze_lock);
+	frozen = percpu_ref_is_dying(&q->q_usage_counter) &&
+		 percpu_ref_is_zero(&q->q_usage_counter);
+	mutex_unlock(&q->mq_freeze_lock);
+
+	return frozen;
+}
+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 2c473c9b8990..6f01971abf7b 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -533,6 +533,7 @@ 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