From mboxrd@z Thu Jan  1 00:00:00 1970
From: Bart Van Assche <Bart.VanAssche@sandisk.com>
Subject: Re: [PATCH v3 3/9] blk-mq: use the introduced
 blk_mq_unquiesce_queue()
Date: Wed, 31 May 2017 15:21:41 +0000
Message-ID: <1496244100.2608.3.camel@sandisk.com>
References: <20170531123706.20885-1-ming.lei@redhat.com>
	<20170531123706.20885-4-ming.lei@redhat.com>
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Cc: "dm-devel@redhat.com" <dm-devel@redhat.com>, "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>, "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
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On Wed, 2017-05-31 at 20:37 +0800, Ming Lei wrote:
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 99e16ac479e3..ffcf05765e2b 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -3031,7 +3031,10 @@ 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);
> +		else
> +			blk_mq_start_stopped_hw_queues(q, false);
>  	} else {
>  		spin_lock_irqsave(q->queue_lock, flags);
>  		blk_start_queue(q);

As I commented on v2, this change is really wrong. All what's needed here is
a call to blk_mq_unquiesce_queue() and nothing else. Adding a call to
blk_mq_start_stopped_hw_queues() is wrong because it makes it impossible to
use the STOPPED flag in the SCSI core to make the block layer core stop calling
.queue_rq() if a SCSI LLD returns "busy".

Bart.