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Wed, 21 Oct 2026 09:32:39 -0700 (PDT) Received: from [192.168.1.106] ([198.8.77.135]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cd6b8482048sm247328a12.7.2026.10.21.09.32.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 Oct 2026 09:32:36 -0700 (PDT) Message-ID: Date: Wed, 21 Oct 2026 10:32:35 -0600 X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] blk-mq: clear stale inactive flag on hctx reuse To: Bart Van Assche , Nirmoy Das Cc: ming.lei@redhat.com, hare@suse.de, dwagner@suse.de, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261020125129.430600-1-nirmoyd@nvidia.com> <29692751-e80e-4f29-a07a-ea0221f1116e@kernel.dk> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/21/26 9:18 AM, Bart Van Assche wrote: > On 10/20/26 7:39 AM, Jens Axboe wrote: >> On 10/20/26 8:13 AM, Bart Van Assche wrote: >>> On 10/20/26 5:51 AM, Nirmoy Das wrote: >>>> diff --git a/block/blk-mq.c b/block/blk-mq.c >>>> index 025a799f35b924d..00b75eb95dd943a 100644 >>>> --- a/block/blk-mq.c >>>> +++ b/block/blk-mq.c >>>> @@ -4002,6 +4002,7 @@ static int blk_mq_init_hctx(struct request_queue *q, >>>> goto fail; >>>> hctx->queue_num = hctx_idx; >>>> + clear_bit(BLK_MQ_S_INACTIVE, &hctx->state); >>>> hctx->tags = set->tags[hctx_idx]; >>> >>> Why clear_bit() instead of __clear_bit()? >> >> Since this isn't a hot path at all, going into details like >> that does more harm than good. clear_bit() is totally fine >> and honestly preferred. > > Although I'm fine with the patch as-is, I want to clarify that > the concern behind my reply is code readability rather than a > micro-optimization. No other context should be accessing a hctx while > blk_mq_init_hctx() is in progress. Using clear_bit() instead of > __clear_bit() might make readers of this code wonder whether any other > context might be accessing the hctx concurrently with the > blk_mq_init_hctx() call. I know that was your intent, but it just reads the opposite to me. Whenever someone uses the __ variants it should only be for optimization purposes, and preferably with a comment explaining why it's safe. Unless there's a reason to do so, using the normal variants is just preferable to me. -- Jens Axboe