block: do not notify urgent request, when flush with data in flight

MMC device driver implements URGENT request execution with priority
(using stop flow), as a result currently running (and prepared) request
may be reinserted back into I/O scheduler. This will break block layer
logic of flushes (flush request should not be inserted into I/O scheduler).

Block layer flush machinery keep q->flush_data_in_flight list updated with
started but not completed flush requests with data (REQ_FUA).

This change will not notify underling block device driver about pending
urgent request during flushes in flight.

Change-Id: I8b654925a3c989250fcb8f4f7c998795fb203923
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>

block/blk-core.c

@@ -314,7 +314,8 @@ void __blk_run_queue(struct request_queue *q)
 	if (!q->notified_urgent &&
 		q->elevator->type->ops.elevator_is_urgent_fn &&
 		q->urgent_request_fn &&
-		q->elevator->type->ops.elevator_is_urgent_fn(q)) {
+		q->elevator->type->ops.elevator_is_urgent_fn(q) &&
+		list_empty(&q->flush_data_in_flight)) {
 		q->notified_urgent = true;
 		q->urgent_request_fn(q);
 	} else