linux-kernel - Re: [PATCH] blk-mq: move bio merge attempt to blk_mq_submit

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Message-ID: <686b645c-c4e1-357f-7c57-b961a1feeda0@bytedance.com>
Date:   Fri, 12 Aug 2022 22:48:20 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blk-mq: move bio merge attempt to blk_mq_submit_bio()

On 2022/8/12 20:40, Jens Axboe wrote:
> On 8/12/22 2:39 AM, Chengming Zhou wrote:
>> We will try to get request from cache before alloc request, in
>> both cases will first attempt bio merge.
>>
>> This patch move this common part to blk_mq_submit_bio(), which
>> simplify the code and avoid passing in the pointer of bio.
> 
> I don't think this will work. If we get a cached request, then we
> know we have a reference to the queue. If you swap these around,
> then that's no longer the case and we can have a use-after-free if
> the queue goes away.
> 

Sorry, thanks for your reply!