Re: [PATCH v2 9/9] block: Do not accept any requests while suspended

[Can Guo <cang@codeaurora.org>]

On 2020-11-16 11:04, Bart Van Assche wrote:
> From: Alan Stern <stern@rowland.harvard.edu>
> 
> blk_queue_enter() accepts BLK_MQ_REQ_PREEMPT independent of the runtime
> power management state. Since 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_PREEMPT requests to a device that is runtime-
> suspended causes runtime-suspended block 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_PREEMPT 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: 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>

Reviewed-by: Can Guo <cang@codeaurora.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 ]
> ---
>  block/blk-core.c |  6 +++---
>  block/blk-pm.h   | 14 +++++++++-----
>  2 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index a00bce9f46d8..230880cbf8c8 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -440,7 +440,8 @@ int blk_queue_enter(struct request_queue *q,
> blk_mq_req_flags_t flags)
>  			 * responsible for ensuring that that counter is
>  			 * globally visible before the queue is unfrozen.
>  			 */
> -			if (pm || !blk_queue_pm_only(q)) {
> +			if ((pm && q->rpm_status != RPM_SUSPENDED) ||
> +			    !blk_queue_pm_only(q)) {
>  				success = true;
>  			} else {
>  				percpu_ref_put(&q->q_usage_counter);
> @@ -465,8 +466,7 @@ int blk_queue_enter(struct request_queue *q,
> blk_mq_req_flags_t flags)
> 
>  		wait_event(q->mq_freeze_wq,
>  			   (!q->mq_freeze_depth &&
> -			    (pm || (blk_pm_request_resume(q),
> -				    !blk_queue_pm_only(q)))) ||
> +			    blk_pm_resume_queue(pm, q)) ||
>  			   blk_queue_dying(q));
>  		if (blk_queue_dying(q))
>  			return -ENODEV;
> diff --git a/block/blk-pm.h b/block/blk-pm.h
> index ea5507d23e75..a2283cc9f716 100644
> --- a/block/blk-pm.h
> +++ b/block/blk-pm.h
> @@ -6,11 +6,14 @@
>  #include <linux/pm_runtime.h>
> 
>  #ifdef CONFIG_PM
> -static inline void blk_pm_request_resume(struct request_queue *q)
> +static inline int blk_pm_resume_queue(const bool pm, struct 
> request_queue *q)
>  {
> -	if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
> -		       q->rpm_status == RPM_SUSPENDING))
> -		pm_request_resume(q->dev);
> +	if (!q->dev || !blk_queue_pm_only(q))
> +		return 1;	/* Nothing to do */
> +	if (pm && q->rpm_status != RPM_SUSPENDED)
> +		return 1;	/* Request allowed */
> +	pm_request_resume(q->dev);
> +	return 0;
>  }
> 
>  static inline void blk_pm_mark_last_busy(struct request *rq)
> @@ -44,8 +47,9 @@ static inline void blk_pm_put_request(struct request 
> *rq)
>  		--rq->q->nr_pending;
>  }
>  #else
> -static inline void blk_pm_request_resume(struct request_queue *q)
> +static inline int blk_pm_resume_queue(const bool pm, struct 
> request_queue *q)
>  {
> +	return 1;
>  }
> 
>  static inline void blk_pm_mark_last_busy(struct request *rq)