blk-mq: put driver tag if dispatch budget can't be got

We have to put the driver tag if dispatch budget can't be got, otherwise
it might cause IO deadlock, especially in case that size of tags is very
small.

Fixes: de1482974080(blk-mq: introduce .get_budget and .put_budget in blk_mq_ops)
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c501cbd0de93f324b2f078024432a643d51e4ebc..3d759bb8a5bb5134ecc413d0c45a3ff6e9c1836e 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1080,8 +1080,10 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
                        }
                }
 
-               if (!got_budget && !blk_mq_get_dispatch_budget(hctx))
+               if (!got_budget && !blk_mq_get_dispatch_budget(hctx)) {
+                       blk_mq_put_driver_tag(rq);
                        break;
+               }
 
                list_del_init(&rq->queuelist);