linux-kernel - Re: Fix potential data loss and corruption due to Incorrect BIO Chain Handling

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Message-ID: <CAHc6FU7+riVQBX7L2uk64A355rF+DfQ6xhP425ruQ76d_SDPGA@mail.gmail.com>
Date: Sat, 22 Nov 2025 15:56:58 +0100
From: Andreas Gruenbacher <agruenba@...hat.com>
To: Ming Lei <ming.lei@...hat.com>
Cc: Stephen Zhang <starzhangzsd@...il.com>, linux-kernel@...r.kernel.org, 
	linux-block@...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, 
	zhangshida@...inos.cn
Subject: Re: Fix potential data loss and corruption due to Incorrect BIO Chain Handling

On Sat, Nov 22, 2025 at 1:07 PM Ming Lei <ming.lei@...hat.com> wrote:
> > static void bio_chain_endio(struct bio *bio)
> > {
> >         bio_endio(__bio_chain_endio(bio));
> > }
>
> bio_chain_endio() never gets called really, which can be thought as `flag`,

That's probably where this stops being relevant for the problem
reported by Stephen Zhang.

> and it should have been defined as `WARN_ON_ONCE(1);` for not confusing people.

But shouldn't bio_chain_endio() still be fixed to do the right thing
if called directly, or alternatively, just BUG()? Warning and still
doing the wrong thing seems a bit bizarre.

I also see direct bi_end_io calls in erofs_fileio_ki_complete(),
erofs_fscache_bio_endio(), and erofs_fscache_submit_bio(), so those
are at least confusing.

Thanks,
Andreas