This is a note to let you know that I've just added the patch titled blk-mq: Put driver tag in blk_mq_dispatch_rq_list() when no budget to the 5.6-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: blk-mq-put-driver-tag-in-blk_mq_dispatch_rq_list-whe.patch and it can be found in the queue-5.6 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 2ceca3e0115f126766317741a47f90bfe0d30873 Author: John Garry <john.garry@xxxxxxxxxx> Date: Thu Apr 16 19:18:51 2020 +0800 blk-mq: Put driver tag in blk_mq_dispatch_rq_list() when no budget [ Upstream commit 5fe56de799ad03e92d794c7936bf363922b571df ] If in blk_mq_dispatch_rq_list() we find no budget, then we break of the dispatch loop, but the request may keep the driver tag, evaulated in 'nxt' in the previous loop iteration. Fix by putting the driver tag for that request. Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx> Signed-off-by: John Garry <john.garry@xxxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/block/blk-mq.c b/block/blk-mq.c index 37ff8dfb8ab9f..2c3a1b2e07537 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1205,8 +1205,10 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, rq = list_first_entry(list, struct request, queuelist); hctx = rq->mq_hctx; - 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; + } if (!blk_mq_get_driver_tag(rq)) { /*