[PATCH V2] blk-mq: put driver tag if dispatch budget can't be got

* [PATCH V2] blk-mq: put driver tag if dispatch budget can't be got
@ 2017-11-08  1:11 Ming Lei
  2017-11-08 18:19 ` Jens Axboe
  0 siblings, 1 reply; 2+ messages in thread
From: Ming Lei @ 2017-11-08  1:11 UTC (permalink / raw)
  To: Jens Axboe, linux-block, Christoph Hellwig
  Cc: Omar Sandoval, Bart Van Assche, Hannes Reinecke, Ming Lei

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>
---
V2:
	add Fixes tag

 block/blk-mq.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c501cbd0de93..3d759bb8a5bb 100644
--- 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);
 
-- 
2.9.5

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