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Date:   Wed, 3 Feb 2021 11:09:55 -0500
From:   Mike Snitzer <snitzer@redhat.com>
To:     Sergei Shtepa <sergei.shtepa@veeam.com>
Cc:     Damien.LeMoal@wdc.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, pavgel.tide@veeam.com
Subject: Re: [PATCH v4 3/6] block: add blk_mq_is_queue_frozen()
Message-ID: <20210203160955.GA21359@redhat.com>
References: <1612367638-3794-1-git-send-email-sergei.shtepa@veeam.com>
 <1612367638-3794-4-git-send-email-sergei.shtepa@veeam.com>
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On Wed, Feb 03 2021 at 10:53am -0500,
Sergei Shtepa <sergei.shtepa@veeam.com> wrote:

> 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
> 

This needs to come before patch 2 (since patch 2 uses it).

Mike