Re: [PATCH v5 8/8] block: Do not accept any requests while suspended

From: Hannes Reinecke <hare@suse.de>
To: Bart Van Assche <bvanassche@acm.org>,
	"Martin K . Petersen" <martin.petersen@oracle.com>
Cc: "James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
	Ming Lei <ming.lei@redhat.com>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	Alan Stern <stern@rowland.harvard.edu>,
	Can Guo <cang@codeaurora.org>,
	Stanley Chu <stanley.chu@mediatek.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Martin Kepplinger <martin.kepplinger@puri.sm>
Subject: Re: [PATCH v5 8/8] block: Do not accept any requests while suspended
Date: Wed, 9 Dec 2020 08:36:26 +0100	[thread overview]
Message-ID: <b257a342-0066-60a6-0bd1-801f502b6d96@suse.de> (raw)
In-Reply-To: <20201209052951.16136-9-bvanassche@acm.org>

On 12/9/20 6:29 AM, Bart Van Assche wrote:
> From: Alan Stern <stern@rowland.harvard.edu>
> 
> blk_queue_enter() accepts BLK_MQ_REQ_PM requests independent of the runtime
> power management state. Now that SCSI domain validation no longer depends
> on this behavior, modify the behavior of blk_queue_enter() as follows:
> - Do not accept any requests while suspended.
> - Only process power management requests while suspending or resuming.
> 
> Submitting BLK_MQ_REQ_PM requests to a device that is runtime suspended
> causes runtime-suspended devices not to resume as they should. The request
> which should cause a runtime resume instead gets issued directly, without
> resuming the device first. Of course the device can't handle it properly,
> the I/O fails, and the device remains suspended.
> 
> The problem is fixed by checking that the queue's runtime-PM status
> isn't RPM_SUSPENDED before allowing a request to be issued, and
> queuing a runtime-resume request if it is.  In particular, the inline
> blk_pm_request_resume() routine is renamed blk_pm_resume_queue() and
> the code is unified by merging the surrounding checks into the
> routine.  If the queue isn't set up for runtime PM, or there currently
> is no restriction on allowed requests, the request is allowed.
> Likewise if the BLK_MQ_REQ_PM flag is set and the status isn't
> RPM_SUSPENDED.  Otherwise a runtime resume is queued and the request
> is blocked until conditions are more suitable.
> 
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Can Guo <cang@codeaurora.org>
> Cc: Stanley Chu <stanley.chu@mediatek.com>
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Reported-and-tested-by: Martin Kepplinger <martin.kepplinger@puri.sm>
> Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> [ bvanassche: modified commit message and removed Cc: stable because without
>    the previous patches from this series this patch would break parallel SCSI
>    domain validation + introduced queue_rpm_status() ]
> ---
>   block/blk-core.c       |  7 ++++---
>   block/blk-pm.h         | 14 +++++++++-----
>   include/linux/blkdev.h | 12 ++++++++++++
>   3 files changed, 25 insertions(+), 8 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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