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([2400:79e0:1203:64b0:f2:8f2c:d78f:adf4]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-38fb2b0f82csm570584a91.2.2026.07.31.11.02.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 31 Jul 2026 11:02:13 -0700 (PDT) Message-ID: Date: Sat, 1 Aug 2026 02:02:10 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] blk-wbt: Always change enable_state to MANUAL when setting latency To: yukuai@fygo.io, Tang Yizhou , axboe@kernel.dk, guzebing1612@gmail.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260717125021.88825-1-yizhou.tang@shopee.com> <2c695292-2fa6-45c1-86e9-d4bf0100debb@fygo.io> Content-Language: en-US From: Tang Yizhou In-Reply-To: <2c695292-2fa6-45c1-86e9-d4bf0100debb@fygo.io> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 24/7/26 2:51 pm, yu kuai wrote: > 在 2026/7/17 20:50, Tang Yizhou 写道: > >> From: Tang Yizhou >> >> Commit 1e56f30a73f3 ("block: Make WBT latency writes honor enable >> state") compares only the boolean enabled state in the no-op check. >> Writing the current latency value while WBT is in WBT_STATE_ON_DEFAULT >> is therefore still skipped, and enable_state is not changed to >> WBT_STATE_ON_MANUAL. A subsequent elevator switch to BFQ then disables >> WBT through wbt_disable_default(), silently discarding the explicit >> sysfs setting: >> >> # enable_state = WBT_STATE_ON_DEFAULT, min_lat_nsec = 2000000 >> echo 2000 > /sys/block/nullb0/queue/wbt_lat_usec # skipped as a no-op >> echo bfq > /sys/block/nullb0/queue/scheduler >> cat /sys/block/nullb0/queue/wbt_lat_usec # 0, WBT disabled >> >> Skip the update only if the stored latency matches and enable_state >> already equals the exact target state: WBT_STATE_ON_MANUAL for a >> non-zero value, WBT_STATE_OFF_MANUAL for zero. >> >> A write that passes the check then reaches wbt_set_min_lat(), which >> performs the actual transition to the MANUAL state. >> >> Rename the helper to wbt_lat_changed() to improve readability. >> >> Fixes: 1e56f30a73f3 ("block: Make WBT latency writes honor enable state") >> Signed-off-by: Tang Yizhou >> --- >> block/blk-wbt.c | 14 +++++++++++--- >> 1 file changed, 11 insertions(+), 3 deletions(-) > Reviewed-by: Yu Kuai > Hi Jens, if there are no further objections, could this patch be merged? -- Best Regards, Yi