blk-mq: don't lose requests if a stopped queue restarts

[linux-2.6-block.git] / block / blk-mq.c

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 76f460e36f1dd94a0bd40dc3647c638fa79fe538..e68b71b85a7eaf0e3097debe8bf4dc4078e7a038 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -858,6 +858,16 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
                spin_lock(&hctx->lock);
                list_splice(&rq_list, &hctx->dispatch);
                spin_unlock(&hctx->lock);
+               /*
+                * the queue is expected stopped with BLK_MQ_RQ_QUEUE_BUSY, but
+                * it's possible the queue is stopped and restarted again
+                * before this. Queue restart will dispatch requests. And since
+                * requests in rq_list aren't added into hctx->dispatch yet,
+                * the requests in rq_list might get lost.
+                *
+                * blk_mq_run_hw_queue() already checks the STOPPED bit
+                **/
+               blk_mq_run_hw_queue(hctx, true);
        }
 }