linux-kernel - Re: [PATCH RFC 2/7] md/raid0: convert raid0_handle_discard() to use bio_submit

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Message-ID: <2984b719-f555-7588-fa2a-1f78d2691e8a@huaweicloud.com>
Date: Tue, 26 Aug 2025 09:08:33 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Christoph Hellwig <hch@...radead.org>, Yu Kuai <yukuai1@...weicloud.com>
Cc: colyli@...nel.org, hare@...e.de, tieren@...as.com, axboe@...nel.dk,
 tj@...nel.org, josef@...icpanda.com, song@...nel.org,
 akpm@...ux-foundation.org, neil@...wn.name, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
 linux-raid@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
 johnny.chenyi@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH RFC 2/7] md/raid0: convert raid0_handle_discard() to use
 bio_submit_split()

Hi,

在 2025/08/25 18:57, Christoph Hellwig 写道:
> On Mon, Aug 25, 2025 at 05:36:55PM +0800, Yu Kuai wrote:
>> +		bio = bio_submit_split(bio,
>> +				zone->zone_end - bio->bi_iter.bi_sector,
>> +				&mddev->bio_set);
> 
> Do you know why raid0 and linear use mddev->bio_set for splitting
> instead of their own split bio_sets like raid1/10/5?  Is this safe?
> 

I think it's not safe, as mddev->bio_split pool size is just 2, reuse
this pool to split multiple times before submitting will need greate
pool size to make this work.

By the way, do you think it's better to increate disk->bio_split pool
size to 4 and convert all mdraid internal split to use disk->bio_split
directly?

Thanks,
Kuai

> Otherwise this looks nice.
> .
>