block: handle blk_pm_resume_request() requests in blk_execute_rq_nowait()

For blk_pm_resume_request() requests (which are used only by IDE subsystem
currently) the queue is stopped so we need to call ->request_fn explicitly.

Thanks to:
- Rafael for reporting/bisecting the bug
- Borislav/Rafael for testing the fix

This is a preparation for converting IDE to use blk_execute_rq().

Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Borislav Petkov <petkovbb@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

block/blk-exec.c

@@ -58,6 +58,9 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
 	spin_lock_irq(q->queue_lock);
 	__elv_add_request(q, rq, where, 1);
 	__generic_unplug_device(q);
+	/* the queue is stopped so it won't be plugged+unplugged */
+	if (blk_pm_resume_request(rq))
+		q->request_fn(q);
 	spin_unlock_irq(q->queue_lock);
 }
 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);