linux-kernel - Re: [PATCH RFC 1/7] block: export helper bio_submit

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Message-ID: <aKxApo1u8j-ZNOaI@infradead.org>
Date: Mon, 25 Aug 2025 03:53:26 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: hch@...radead.org, colyli@...nel.org, hare@...e.de, tieren@...as.com,
	axboe@...nel.dk, tj@...nel.org, josef@...icpanda.com,
	song@...nel.org, yukuai3@...wei.com, 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
Subject: Re: [PATCH RFC 1/7] block: export helper bio_submit_split()

On Mon, Aug 25, 2025 at 05:36:54PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> No functional changes are intended, some drivers like mdraid will split
> bio by internal processing, prepare to unify bio split codes.

Maybe name the exported helper bio_submit_split_bioset and keep
bio_submit_split() as a wrapper that passes the default split
bioset to keep the code a bit tidyer in blk-merge.c?

> +struct bio *bio_submit_split(struct bio *bio, int split_sectors,
> +			     struct bio_set *bs)
>  {
> +	struct bio *split;
> +
>  	if (unlikely(split_sectors < 0))
>  		goto error;
>  
> -	if (split_sectors) {
> -		struct bio *split;
> +	if (!split_sectors)
> +		return bio;
>  
> -		split = bio_split(bio, split_sectors, GFP_NOIO,
> -				&bio->bi_bdev->bd_disk->bio_split);
> -		if (IS_ERR(split)) {
> -			split_sectors = PTR_ERR(split);
> -			goto error;
> -		}
> -		split->bi_opf |= REQ_NOMERGE;
> -		blkcg_bio_issue_init(split);
> -		bio_chain(split, bio);
> -		trace_block_split(split, bio->bi_iter.bi_sector);
> -		WARN_ON_ONCE(bio_zone_write_plugging(bio));
> -		submit_bio_noacct(bio);

Maybe skip the reformatting which makes this much harder to read?
If you think it is useful it can be done in a separate patch.