On Thu, Jul 12, 2018 at 12:29:05AM +0800, Ming Lei wrote:
> This patch introduces blk_mq_pm_add_request() which is called after
> allocating one request. Also blk_mq_pm_put_request() is introduced
> and called after one request is freed.
>
> For blk-mq, it can be quite expensive to accounting in-flight IOs,
> so this patch calls pm_runtime_mark_last_busy() simply after each IO
> is done, instead of doing that only after the last in-flight IO is done.
> This way is still workable, since the active non-PM IO will be checked
> in blk_pre_runtime_suspend(), and runtime suspend will be prevented
> if there is any active non-PM IO.
>
> Also makes blk_post_runtime_resume() to cover blk-mq.
>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Bart Van Assche <bart.vanassche@xxxxxxx>
> Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxxxxxxx>
> Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
> Cc: linux-scsi@xxxxxxxxxxxxxxx
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> block/blk-core.c | 12 ++++++++++--
> block/blk-mq.c | 24 ++++++++++++++++++++++++
> 2 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> 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) {
> ret = -EBUSY;
> pm_runtime_mark_last_busy(q->dev);
> } else {
Looks there is one big issue, one new IO may come just after reading
'active' and before writing RPM_SUSPENDING to q->rpm_status, and both
the suspending and the new IO may be in-progress at the same time.
Thanks,
Ming
