linux-kernel - Re: [PATCH v2 12/12] nvmet: use bio_chain_and

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CANubcdWAk2Mh5b9stjTh8N84jq+XAgaR3n2-VYRinU9ERtJLUw@mail.gmail.com>
Date: Mon, 1 Dec 2025 10:41:06 +0800
From: Stephen Zhang <starzhangzsd@...il.com>
To: Sagi Grimberg <sagi@...mberg.me>
Cc: Johannes.Thumshirn@....com, hch@...radead.org, ming.lei@...hat.com, 
	linux-block@...r.kernel.org, linux-bcache@...r.kernel.org, 
	nvdimm@...ts.linux.dev, virtualization@...ts.linux.dev, 
	linux-nvme@...ts.infradead.org, gfs2@...ts.linux.dev, ntfs3@...ts.linux.dev, 
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	zhangshida@...inos.cn, Andreas Gruenbacher <agruenba@...hat.com>, 
	Gao Xiang <hsiangkao@...ux.alibaba.com>
Subject: Re: [PATCH v2 12/12] nvmet: use bio_chain_and_submit to simplify bio chaining

Sagi Grimberg <sagi@...mberg.me> 于2025年12月1日周一 07:03写道：
>
> Acked-by: Sagi Grimberg <sagi@...mberg.me>

Hello,

I already dropped this patch in v3:
https://lore.kernel.org/all/20251129090122.2457896-1-zhangshida@kylinos.cn/
The reason is that the order of operations is critical. In the original code::
----------------
...
bio->bi_end_io = nvmet_bio_done;

for_each_sg(req->sg, sg, req->sg_cnt, i) {
...
          struct bio *prev = bio;
....
          bio_chain(bio, prev);
          submit_bio(prev);
}
----------------

the oldest bio (i.e., prev) retains the real bi_end_io function:

bio -> bio -> ... -> prev
However, using bio_chain_and_submit(prev, bio) would create the reverse chain:

prev -> prev -> ... -> bio

where the newest bio would hold the real bi_end_io function, which does not
match the required behavior in this context.

Thanks,
Shida