linux-kernel - [PATCH AUTOSEL 5.4 23/24] block: update hctx map when use multiple maps

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Date:   Tue, 23 Jun 2020 13:35:58 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Weiping Zhang <zhangweiping@...iglobal.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 23/24] block: update hctx map when use multiple maps

From: Weiping Zhang <zhangweiping@...iglobal.com>

[ Upstream commit fe35ec58f0d339221643287bbb7cee15c93a5389 ]

There is an issue when tune the number for read and write queues,
if the total queue count was not changed. The hctx->type cannot
be updated, since __blk_mq_update_nr_hw_queues will return directly
if the total queue count has not been changed.

Reproduce:

dmesg | grep "default/read/poll"
[    2.607459] nvme nvme0: 48/0/0 default/read/poll queues
cat /sys/kernel/debug/block/nvme0n1/hctx*/type | sort | uniq -c
     48 default

tune the write queues to 24:
echo 24 > /sys/module/nvme/parameters/write_queues
echo 1 > /sys/block/nvme0n1/device/reset_controller

dmesg | grep "default/read/poll"
[  433.547235] nvme nvme0: 24/24/0 default/read/poll queues

cat /sys/kernel/debug/block/nvme0n1/hctx*/type | sort | uniq -c
     48 default

The driver's hardware queue mapping is not same as block layer.

Signed-off-by: Weiping Zhang <zhangweiping@...iglobal.com>
Reviewed-by: Ming Lei <ming.lei@...hat.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 0550366e25d8b..f1b930a300a38 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3279,7 +3279,9 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 
 	if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
 		nr_hw_queues = nr_cpu_ids;
-	if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
+	if (nr_hw_queues < 1)
+		return;
+	if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues)
 		return;
 
 	list_for_each_entry(q, &set->tag_list, tag_set_list)
-- 
2.25.1