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Tue, 12 Aug 2025 08:43:03 -0700 (PDT) Received: from localhost ([101.82.110.149]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-76bcce6f319sm29815344b3a.18.2025.08.12.08.43.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Aug 2025 08:43:02 -0700 (PDT) From: Julian Sun X-Google-Original-From: Julian Sun To: linux-block@vger.kernel.org Cc: axboe@kernel.dk, nilay@linux.ibm.com, ming.lei@redhat.com, Julian Sun , stable@vger.kernel.org Subject: [PATCH v2] block: restore default wbt enablement Date: Tue, 12 Aug 2025 23:42:57 +0800 Message-Id: <20250812154257.57540-1-sunjunchao@bytedance.com> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The commit 245618f8e45f ("block: protect wbt_lat_usec using q->elevator_lock") protected wbt_enable_default() with q->elevator_lock; however, it also placed wbt_enable_default() before blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);, resulting in wbt failing to be enabled. Moreover, the protection of wbt_enable_default() by q->elevator_lock was removed in commit 78c271344b6f ("block: move wbt_enable_default() out of queue freezing from sched ->exit()"), so we can directly fix this issue by placing wbt_enable_default() after blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);. Additionally, this issue also causes the inability to read the wbt_lat_usec file, and the scenario is as follows: root@q:/sys/block/sda/queue# cat wbt_lat_usec cat: wbt_lat_usec: Invalid argument root@q:/data00/sjc/linux# ls /sys/kernel/debug/block/sda/rqos cannot access '/sys/kernel/debug/block/sda/rqos': No such file or directory root@q:/data00/sjc/linux# find /sys -name wbt /sys/kernel/debug/tracing/events/wbt After testing with this patch, wbt can be enabled normally. Signed-off-by: Julian Sun Cc: stable@vger.kernel.org Fixes: 245618f8e45f ("block: protect wbt_lat_usec using q->elevator_lock") --- Changed in v2: - Improved commit message and comment - Added Fixes and Cc stable block/blk-sysfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 396cded255ea..979f01bbca01 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -903,9 +903,9 @@ int blk_register_queue(struct gendisk *disk) if (queue_is_mq(q)) elevator_set_default(q); - wbt_enable_default(disk); blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q); + wbt_enable_default(disk); /* Now everything is ready and send out KOBJ_ADD uevent */ kobject_uevent(&disk->queue_kobj, KOBJ_ADD); -- 2.39.5