linux-kernel - Re: [PATCH v2] blk-ioc: don't hold queue_lock for ioc_lookup

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Message-ID: <0f3f0978-eb42-4d83-81ad-e42cc482d674@kernel.org>
Date: Mon, 28 Jul 2025 12:53:04 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Yu Kuai <yukuai@...nel.org>, jack@...e.cz, axboe@...nel.dk,
 linux-block@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, yukuai3@...wei.com, yi.zhang@...wei.com,
 yangerkun@...wei.com, johnny.chenyi@...wei.com
Subject: Re: [PATCH v2] blk-ioc: don't hold queue_lock for ioc_lookup_icq()

On 7/26/25 3:03 AM, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Currently issue io can grab queue_lock three times from bfq_bio_merge(),
> bfq_limit_depth() and bfq_prepare_request(), the queue_lock is not
> necessary if icq is already created because both queue and ioc can't be
> freed before io issuing is done, hence remove the unnecessary queue_lock
> and use rcu to protect radix tree lookup.
> 
> Noted this is also a prep patch to support request batch dispatching[1].
> 
> [1] https://lore.kernel.org/all/20250722072431.610354-1-yukuai1@huaweicloud.com/
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Look OK.

Reviewed-by: Damien Le Moal <dlemoal@...nel.org>

-- 
Damien Le Moal
Western Digital Research