linux-kernel - Re: [PATCH v3 3/9] block: prevent race condition on bi_status in __bio_chain

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Message-ID: <aS0yXeoUFybWlTxc@infradead.org>
Date: Sun, 30 Nov 2025 22:14:53 -0800
From: Christoph Hellwig <hch@...radead.org>
To: zhangshida <starzhangzsd@...il.com>
Cc: Johannes.Thumshirn@....com, hch@...radead.org, agruenba@...hat.com,
	ming.lei@...hat.com, hsiangkao@...ux.alibaba.com,
	csander@...estorage.com, linux-block@...r.kernel.org,
	linux-bcache@...r.kernel.org, nvdimm@...ts.linux.dev,
	virtualization@...ts.linux.dev, ntfs3@...ts.linux.dev,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	zhangshida@...inos.cn
Subject: Re: [PATCH v3 3/9] block: prevent race condition on bi_status in
 __bio_chain_endio

On Sat, Nov 29, 2025 at 05:01:16PM +0800, zhangshida wrote:
> From: Shida Zhang <zhangshida@...inos.cn>
> 
> Andreas point out that multiple completions can race setting
> bi_status.
> 
> The check (parent->bi_status) and the subsequent write are not an
> atomic operation. The value of parent->bi_status could have changed
> between the time you read it for the if check and the time you write
> to it. So we use cmpxchg to fix the race, as suggested by Christoph.

Looks good:

Reviewed-by: Christoph Hellwig <hch@....de>