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

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Message-ID: <dc98ae47-5abf-05dc-5441-547cbb4b9c80@huaweicloud.com>
Date: Mon, 25 Aug 2025 17:49:01 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Christoph Hellwig <hch@...radead.org>, Yu Kuai <yukuai1@...weicloud.com>
Cc: 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,
 tieren@...as.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] block: fix disordered IO in the case recursive split

Hi,

在 2025/08/25 17:17, Christoph Hellwig 写道:
> 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.
> 

I just send a new rfc verion to unify block layer and mdraid to use
the same helper bio_submit_split(), and convert only that helper to
insert split bio to the head of current->bio_list(). And probably
blk-crypto-fallback can use this new helper as well.

Can you take a look? This is the proper solution that I can think of
for now.

Thanks,
Kuai

> .
>