Re: [PATCH RFC 3/4] blk-mq: prepare for supporting runtime PM

[Christoph Hellwig <hch@lst.de>]

> index c4b57d8806fe..bf66d561980d 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -3804,12 +3804,17 @@ EXPORT_SYMBOL(blk_pm_runtime_init);
>  int blk_pre_runtime_suspend(struct request_queue *q)
>  {
>  	int ret = 0;
> +	bool active;
>  
>  	if (!q->dev)
>  		return ret;
>  
>  	spin_lock_irq(q->queue_lock);
> -	if (q->nr_pending) {
> +	if (!q->mq_ops)
> +		active = !!q->nr_pending;
> +	else
> +		active = !blk_mq_pm_queue_idle(q);
> +	if (active) {

We shouldn't really need queue_lock for blk-mq.  Also the !! is not
really needed when assigning to a bool.

> +static void blk_mq_pm_add_request(struct request_queue *q, struct request *rq)
> +{
> +	if (!blk_mq_support_runtime_pm(q))
> +		return;
> +
> +	if (q->dev && !(rq->rq_flags & RQF_PM) &&
> +	    (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
> +		pm_request_resume(q->dev);

blk_mq_support_runtime_pm already checks for q->dev.   Also to mee
it sems just opencoding blk_mq_pm_add_request / blk_mq_pm_put_request
in the callers would seems more obvious.

> @@ -1841,6 +1863,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
>  
>  	rq_qos_track(q, rq, bio);
>  
> +	blk_mq_pm_add_request(q, rq);

This doesn't seem to handle passthrough requests and not actually
pair with blk_mq_free_request, is that intentional?