On Fri, Sep 08, 2017 at 04:52:25PM -0700, Bart Van Assche wrote:
> Instead of allowing request allocation to succeed for suspended
> request queues and only to process power management requests, make
> blk_get_request() wait until the request queue is resumed for
> requests that are not power management requests.
>
> This patch avoids that resume does not occur if the maximum queue
> depth is reached when a power management request is submitted.
>
> Note: this patch affects the behavior of scsi_device_quiesce() only
> if that function is called from inside a power management callback.
> This patch does not affect the behavior of scsi_device_quiesce()
> when a call of that function is triggered by writing "quiesce" into
> /sys/class/scsi_device/*/device/state.
>
> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> block/blk-core.c | 60 +++++++++++++++++++++++++++-----------------------
> block/blk.h | 12 ++++++++++
> include/linux/blkdev.h | 1 +
> 3 files changed, 45 insertions(+), 28 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index bb53c6b58e8c..cd2700c763ed 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1325,6 +1325,24 @@ static struct request *__get_request(struct request_list *rl, unsigned int op,
> return ERR_PTR(-ENOMEM);
> }
>
> +#ifdef CONFIG_PM
> +static bool blk_wait_until_active(struct request_queue *q, bool wait)
> + __releases(q->queue_lock)
> + __acquires(q->queue_lock)
> +{
> + if (wait)
> + wait_event_lock_irq(q->rpm_active_wq,
> + q->rpm_status == RPM_ACTIVE,
> + *q->queue_lock);
> + return q->rpm_status == RPM_ACTIVE;
If runtime PM is disabled via /sys/.../power/control, q->rpm_status
can be always ACTIVE, even during system suspend, then you can't
prevent any new request allocation at that time.
--
Ming
