linux-kernel - Re: [PATCH 1/9] block: fix data loss and stale date exposure problems during append write

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Message-ID: <CAHc6FU7NpnmbOGZB8Z7VwOBoZLm8jZkcAk_2yPANy9=DYS67-A@mail.gmail.com>
Date: Fri, 21 Nov 2025 17:13:20 +0100
From: Andreas Gruenbacher <agruenba@...hat.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: zhangshida <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: [PATCH 1/9] block: fix data loss and stale date exposure problems
 during append write

On Fri, Nov 21, 2025 at 11:38 AM Christoph Hellwig <hch@...radead.org> wrote:
> On Fri, Nov 21, 2025 at 04:17:40PM +0800, zhangshida wrote:
> > From: Shida Zhang <zhangshida@...inos.cn>
> >
> > Signed-off-by: Shida Zhang <zhangshida@...inos.cn>
> > ---
> >  block/bio.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/block/bio.c b/block/bio.c
> > index b3a79285c27..55c2c1a0020 100644
> > --- a/block/bio.c
> > +++ b/block/bio.c
> > @@ -322,7 +322,7 @@ static struct bio *__bio_chain_endio(struct bio *bio)
> >
> >  static void bio_chain_endio(struct bio *bio)
> >  {
> > -     bio_endio(__bio_chain_endio(bio));
> > +     bio_endio(bio);
>
> I don't see how this can work.  bio_chain_endio is called literally
> as the result of calling bio_endio, so you recurse into that.

Hmm, I don't actually see where: bio_endio() only calls
__bio_chain_endio(), which is fine.

Once bio_chain_endio() only calls bio_endio(), it can probably be
removed in a follow-up patch.

Also, loosely related, what I find slightly odd is this code in
__bio_chain_endio():

        if (bio->bi_status && !parent->bi_status)
                parent->bi_status = bio->bi_status;

I don't think it really matters whether or not parent->bi_status is
already set here?

Also, multiple completions can race setting bi_status, so shouldn't we
at least have a WRITE_ONCE() here and in the other places that set
bi_status?

Thanks,
Andreas