linux-kernel - [PATCH] blk-wbt: fix that 'rwb->wc' is always set to 1 in wbt

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Message-Id: <20221009101038.1692875-1-yukuai1@huaweicloud.com>
Date:   Sun,  9 Oct 2022 18:10:38 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     fengwei.yin@...el.com, ming.lei@...hat.com, axboe@...nel.dk,
        yukuai3@...wei.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai1@...weicloud.com, yi.zhang@...wei.com
Subject: [PATCH] blk-wbt: fix that 'rwb->wc' is always set to 1 in wbt_init()

From: Yu Kuai <yukuai3@...wei.com>

commit 8c5035dfbb94 ("blk-wbt: call rq_qos_add() after wb_normal is
initialized") moves wbt_set_write_cache() before rq_qos_add(), which
is wrong because wbt_rq_qos() is still NULL.

Fix the problem by removing wbt_set_write_cache() and setting 'rwb->wc'
directly. Noted that this patch also remove the redundant setting of
'rab->wc'.

Fixes: 8c5035dfbb94 ("blk-wbt: call rq_qos_add() after wb_normal is initialized")
Reported-by: kernel test robot <yujie.liu@...el.com>
Link: https://lore.kernel.org/r/202210081045.77ddf59b-yujie.liu@intel.com
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
 block/blk-wbt.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 246467926253..c293e08b301f 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -841,12 +841,11 @@ int wbt_init(struct request_queue *q)
 	rwb->last_comp = rwb->last_issue = jiffies;
 	rwb->win_nsec = RWB_WINDOW_NSEC;
 	rwb->enable_state = WBT_STATE_ON_DEFAULT;
-	rwb->wc = 1;
+	rwb->wc = test_bit(QUEUE_FLAG_WC, &q->queue_flags);
 	rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
 	rwb->min_lat_nsec = wbt_default_latency_nsec(q);
 
 	wbt_queue_depth_changed(&rwb->rqos);
-	wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
 
 	/*
 	 * Assign rwb and add the stats callback.
-- 
2.31.1