linux-kernel - [PATCH AUTOSEL 5.4 25/26] blk-mq: Put driver tag in blk_mq_dispatch_rq

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Date:   Fri, 24 Apr 2020 08:23:22 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     John Garry <john.garry@...wei.com>, Ming Lei <ming.lei@...hat.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 25/26] blk-mq: Put driver tag in blk_mq_dispatch_rq_list() when no budget

From: John Garry <john.garry@...wei.com>

[ 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@...hat.com>
Signed-off-by: John Garry <john.garry@...wei.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 a8c1a45cedde0..757c0fd9f0cc2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1232,8 +1232,10 @@ 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)) {
 			/*
-- 
2.20.1