linux-kernel - Re: [PATCH v3 2/2] blk-mq: fix blk_mq_tags double free while nr

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Message-ID: <1366b2ec-cce5-632a-09a6-fba528d11f03@huaweicloud.com>
Date: Thu, 21 Aug 2025 22:57:50 +0800
From: Li Nan <linan666@...weicloud.com>
To: Yu Kuai <yukuai1@...weicloud.com>, yukuai3@...wei.com, axboe@...nel.dk,
 bvanassche@....org, ming.lei@...hat.com, nilay@...ux.ibm.com, hare@...e.de
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com
Subject: Re: [PATCH v3 2/2] blk-mq: fix blk_mq_tags double free while
 nr_requests grown



在 2025/8/21 14:06, Yu Kuai 写道:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> In the case user trigger tags grow by queue sysfs attribute nr_requests,
> hctx->sched_tags will be freed directly and replaced with a new
> allocated tags, see blk_mq_tag_update_depth().
> 
> The problem is that hctx->sched_tags is from elevator->et->tags, while
> et->tags is still the freed tags, hence later elevator exit will try to
> free the tags again, causing kernel panic.
> 
> Fix this problem by replacing et->tags with new allocated tags as well.
> 
> Noted there are still some long term problems that will require some
> refactor to be fixed thoroughly[1].
> 
> [1] https://lore.kernel.org/all/20250815080216.410665-1-yukuai1@huaweicloud.com/
> Fixes: f5a6604f7a44 ("block: fix lockdep warning caused by lock dependency in elv_iosched_store")
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> Reviewed-by: Ming Lei <ming.lei@...hat.com>
> Reviewed-by: Nilay Shroff<nilay@...ux.ibm.com>
> ---

LGTM

Reviewed-by: Li Nan <linan122@...wei.com>

-- 
Thanks,
Nan