linux-kernel - [PATCH AUTOSEL 5.0 44/66] blk-mq: do not reset plug->rq

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Date:   Wed, 24 Apr 2019 10:33:18 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dongli Zhang <dongli.zhang@...cle.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 5.0 44/66] blk-mq: do not reset plug->rq_count before the list is sorted

From: Dongli Zhang <dongli.zhang@...cle.com>

[ Upstream commit bcc816dfe51ab86ca94663c7b225f2d6eb0fddb9 ]

We would never be able to sort the list if we first reset plug->rq_count
which is used in conditional check later.

Fixes: ce5b009cff19 ("block: improve logic around when to sort a plug list")
Reviewed-by: Ming Lei <ming.lei@...hat.com>
Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin (Microsoft) <sashal@...nel.org>
---
 block/blk-mq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 97eba6d23425..5a2585d69c81 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1716,11 +1716,12 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 	unsigned int depth;
 
 	list_splice_init(&plug->mq_list, &list);
-	plug->rq_count = 0;
 
 	if (plug->rq_count > 2 && plug->multiple_queues)
 		list_sort(NULL, &list, plug_rq_cmp);
 
+	plug->rq_count = 0;
+
 	this_q = NULL;
 	this_hctx = NULL;
 	this_ctx = NULL;
-- 
2.19.1