block: don't delay blk_run_queue_async

Let's check a scenario:
1. blk_delay_queue(q, SCSI_QUEUE_DELAY);
2. blk_run_queue_async();
the second one will became a noop, because q->delay_work already has
WORK_STRUCT_PENDING_BIT set, so the delayed work will still run after
SCSI_QUEUE_DELAY. But blk_run_queue_async actually hopes the delayed
work runs immediately.

Fix this by doing a cancel on potentially pending delayed work
before queuing an immediate run of the workqueue.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index a2e58eeb3549..3fe00a14822a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -316,8 +316,10 @@ EXPORT_SYMBOL(__blk_run_queue);
  */
 void blk_run_queue_async(struct request_queue *q)
 {
-        if (likely(!blk_queue_stopped(q)))
+        if (likely(!blk_queue_stopped(q))) {
+                __cancel_delayed_work(&q->delay_work);
                 queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
+        }
 }
 EXPORT_SYMBOL(blk_run_queue_async);