On Mon, 2020-11-16 at 11:04 +0800, 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 <redacted>
Cc: Stanley Chu <redacted>
Cc: Ming Lei <redacted>
Cc: Rafael J. Wysocki <redacted>
Reported-and-tested-by: Martin Kepplinger <redacted>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>

Reviewed-by: Stanley Chu <redacted>