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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Ming Lei <ming.lei@redhat.com>,
        Dongli Zhang <dongli.zhang@oracle.com>,
        Jens Axboe <axboe@kernel.dk>,
        "Sasha Levin (Microsoft)" <sashal@kernel.org>
Subject: [PATCH 5.0 066/122] blk-mq: do not reset plug->rq_count before the list is sorted
Date:   Mon,  6 May 2019 16:32:04 +0200
Message-Id: <20190506143100.884894875@linuxfoundation.org>
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[ 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@redhat.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.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;
-- 
2.20.1