linux-kernel - [PATCH] blk-mq: Put driver tag in blk_mq_dispatch_rq

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Message-ID: <1587035931-125028-1-git-send-email-john.garry@huawei.com>
Date:   Thu, 16 Apr 2020 19:18:51 +0800
From:   John Garry <john.garry@...wei.com>
To:     <axboe@...nel.dk>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <ming.lei@...hat.com>, John Garry <john.garry@...wei.com>
Subject: [PATCH] blk-mq: Put driver tag in blk_mq_dispatch_rq_list() when no budget

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.

Signed-off-by: John Garry <john.garry@...wei.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8e56884fd2e9..a7785df2c944 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1222,8 +1222,10 @@ 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)) {
 			/*
-- 
2.16.4