linux-kernel - Re: [PATCH] block: fix disordered IO in the case recursive split

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Message-ID: <aKwqGHE_ImVwoH6B@infradead.org>
Date: Mon, 25 Aug 2025 02:17:12 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: Christoph Hellwig <hch@...radead.org>, axboe@...nel.dk, neil@...wn.name,
	akpm@...ux-foundation.org, linux-block@...r.kernel.org,
	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	colyli@...nel.org, xni@...hat.com, yi.zhang@...wei.com,
	yangerkun@...wei.com, johnny.chenyi@...wei.com,
	"yukuai (C)" <yukuai3@...wei.com>, tieren@...as.com
Subject: Re: [PATCH] block: fix disordered IO in the case recursive split

On Thu, Aug 21, 2025 at 05:37:15PM +0800, Yu Kuai wrote:
> Fix bio splitting by the crypto fallback code

Yes.

> 
> I'll take look at all the callers of bio_chain(), in theory, we'll have
> different use cases like:
> 
> 1) chain old -> new, or chain new -> old
> 2) put old or new to current->bio_list, currently always in the tail,
> we might want a new case to the head;
> 
> Perhaps it'll make sense to add high level helpers to do the chain
> and resubmit and convert all callers to use new helpers, want do you
> think?

I don't think chaining really is problem here, but more how bios
are split when already in the block layer.  It's been a bit of a
source for problems, so I think we'll need to sort it out.  Especially
as the handling of splits for the same device vs devices below the
current one seems a bit problematic in general.