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

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Message-ID: <54fc027f-f4dc-0412-0d6d-b44a3e644c39@huaweicloud.com>
Date: Thu, 21 Aug 2025 16:56:33 +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,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] block: fix disordered IO in the case recursive split

Hi,

在 2025/08/21 16:43, Christoph Hellwig 写道:
> On Thu, Aug 21, 2025 at 03:47:06PM +0800, Yu Kuai wrote:
>> +	if (current->bio_list) {
>> +		if (bio_flagged(bio, BIO_CHAIN))
>> +			bio_list_add_head(&current->bio_list[0], bio);
>> +		else
>> +			bio_list_add(&current->bio_list[0], bio);
>> +	} else if (!bdev_test_flag(bio->bi_bdev, BD_HAS_SUBMIT_BIO)) {
> 
> This breaks all the code the already chains the right way around,
> and there's quite a bit of that (speaking as someone who created a few
> instances).
> 
> So instead fix your submitter to chain the right way instead.
> 

Can you give some examples as how to chain the right way? BTW, for all
the io split case, should this order be fixed? I feel we should, this
disorder can happen on any stack case, where top max_sector is greater
than stacked disk.

Thanks,
Kuai

> 
> .
>