[PATCH] return remaining jiffies from blk_congestion_wait()

Teach blk_congestion_wait() to return the number of jiffies remaining.  This
is for debug, but it is also nicely consistent.

drivers/block/ll_rw_blk.c

@@ -2040,15 +2040,17 @@ EXPORT_SYMBOL(blk_put_request);
  * If no queues are congested then just wait for the next request to be
  * returned.
  */
-void blk_congestion_wait(int rw, long timeout)
+long blk_congestion_wait(int rw, long timeout)
 {
+	long ret;
 	DEFINE_WAIT(wait);
 	wait_queue_head_t *wqh = &congestion_wqh[rw];
 
 	blk_run_queues();
 	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
-	io_schedule_timeout(timeout);
+	ret = io_schedule_timeout(timeout);
 	finish_wait(wqh, &wait);
+	return ret;
 }
 
 EXPORT_SYMBOL(blk_congestion_wait);

include/linux/blkdev.h

@@ -592,7 +592,7 @@ extern int blk_queue_init_tags(request_queue_t *, int, struct blk_queue_tag *);
 extern void blk_queue_free_tags(request_queue_t *);
 extern int blk_queue_resize_tags(request_queue_t *, int);
 extern void blk_queue_invalidate_tags(request_queue_t *);
-extern void blk_congestion_wait(int rw, long timeout);
+extern long blk_congestion_wait(int rw, long timeout);
 
 extern void blk_rq_bio_prep(request_queue_t *, struct request *, struct bio *);
 extern void blk_rq_prep_restart(struct request *);