Re: [PATCH v2 3/8] blk-mq: use the introduced blk_mq_unquiesce_queue()

[Eduardo Valentin <eduval@amazon.com>]

On Sat, May 27, 2017 at 10:21:21PM +0800, Ming Lei wrote:
> blk_mq_unquiesce_queue() is used for unquiescing the
> queue explicitly, so replace blk_mq_start_stopped_hw_queues()
> with it.
> 
> Cc: linux-nvme@lists.infradead.org
> Cc: linux-scsi@vger.kernel.org
> Cc: dm-devel@redhat.com
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/md/dm-rq.c       | 2 +-
>  drivers/nvme/host/core.c | 2 +-
>  drivers/scsi/scsi_lib.c  | 5 ++++-
>  3 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
> index 2af27026aa2e..673fcf075077 100644
> --- a/drivers/md/dm-rq.c
> +++ b/drivers/md/dm-rq.c
> @@ -71,7 +71,7 @@ static void dm_old_start_queue(struct request_queue *q)
>  
>  static void dm_mq_start_queue(struct request_queue *q)
>  {
> -	blk_mq_start_stopped_hw_queues(q, true);
> +	blk_mq_unquiesce_queue(q);
>  	blk_mq_kick_requeue_list(q);
>  }
>  
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 04e115834702..231d36028afc 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2514,7 +2514,7 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
>  
>  	mutex_lock(&ctrl->namespaces_mutex);
>  	list_for_each_entry(ns, &ctrl->namespaces, list) {
> -		blk_mq_start_stopped_hw_queues(ns->queue, true);
> +		blk_mq_unquiesce_queue(ns->queue);
>  		blk_mq_kick_requeue_list(ns->queue);
>  	}
>  	mutex_unlock(&ctrl->namespaces_mutex);
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 814a4bd8405d..72b11f75719c 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -3030,7 +3030,10 @@ scsi_internal_device_unblock(struct scsi_device *sdev,
>  		return -EINVAL;
>  
>  	if (q->mq_ops) {
> -		blk_mq_start_stopped_hw_queues(q, false);
> +		if (blk_queue_quiesced(q))
> +			blk_mq_unquiesce_queue(q);

Calling this here, at this point means:
		blk_mq_start_stopped_hw_queues(q, true);

Does it make a difference, given that before the code always calling 
		blk_mq_start_stopped_hw_queues(q, false);


> +		else
> +			blk_mq_start_stopped_hw_queues(q, false);

Why do you need to care about the case of !blk_queue_quiesced(q)?

>  	} else {
>  		spin_lock_irqsave(q->queue_lock, flags);
>  		blk_start_queue(q);
> -- 
> 2.9.4
> 
> 

-- 
All the best,
Eduardo Valentin