linux-kernel - Re: [PATCH RFC v3 05/15] block: factor out a helper bio_submit_split

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4f54d81a-d330-44b2-b667-3b13d516c576@acm.org>
Date: Tue, 2 Sep 2025 10:12:23 -0700
From: Bart Van Assche <bvanassche@....org>
To: Yu Kuai <yukuai1@...weicloud.com>, hch@...radead.org, colyli@...nel.org,
 hare@...e.de, dlemoal@...nel.org, tieren@...as.com, axboe@...nel.dk,
 tj@...nel.org, josef@...icpanda.com, song@...nel.org, kmo@...erainc.com,
 satyat@...gle.com, ebiggers@...gle.com, neil@...wn.name,
 akpm@...ux-foundation.org
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 cgroups@...r.kernel.org, linux-raid@...r.kernel.org, yukuai3@...wei.com,
 yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com
Subject: Re: [PATCH RFC v3 05/15] block: factor out a helper
 bio_submit_split_bioset()

On 8/31/25 8:32 PM, 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.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>   block/blk-merge.c      | 63 ++++++++++++++++++++++++++++--------------
>   include/linux/blkdev.h |  2 ++
>   2 files changed, 44 insertions(+), 21 deletions(-)
> 
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 70d704615be5..e1afb07040c0 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -104,34 +104,55 @@ static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim)
>   	return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT;
>   }
>   
> +/**
> + * bio_submit_split_bioset - Submit a bio, splitting it at a designated sector
> + * @bio:		the original bio to be submitted and split
> + * @split_sectors:	the sector count at which to split
> + * @bs:			the bio set used for allocating the new split bio
> + *
> + * The original bio is modified to contain the remaining sectors and submitted.
> + * The caller is responsible for submitting the returned bio.
> + *
> + * If succeed, the newly allocated bio representing the initial part will be
> + * returned, on failure NULL will be returned and original bio will fail.
> + */
> +struct bio *bio_submit_split_bioset(struct bio *bio, unsigned int split_sectors,
> +				    struct bio_set *bs)
> +{
> +	struct bio *split = bio_split(bio, split_sectors, GFP_NOIO, bs);
> +
> +	if (IS_ERR(split)) {
> +		bio->bi_status = errno_to_blk_status(PTR_ERR(split));
> +		bio_endio(bio);
> +		return NULL;
> +	}
> +
> +	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);
> +
> +	return split;
> +}
> +EXPORT_SYMBOL_GPL(bio_submit_split_bioset);
> +
>   static struct bio *bio_submit_split(struct bio *bio, int split_sectors)
>   {
> -	if (unlikely(split_sectors < 0))
> -		goto error;
> +	if (unlikely(split_sectors < 0)) {
> +		bio->bi_status = errno_to_blk_status(split_sectors);
> +		bio_endio(bio);
> +		return NULL;
> +	}
>   
>   	if (split_sectors) {
> -		struct bio *split;
> -
> -		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);
> -		return split;
> +		bio = bio_submit_split_bioset(bio, split_sectors,
> +					 &bio->bi_bdev->bd_disk->bio_split);
> +		if (bio)
> +			bio->bi_opf |= REQ_NOMERGE;
>   	}

This is a good opportunity to reduce the indentation level in this
function by adding something like this above the
bio_submit_split_bioset() call:

if (unlikely(split_sectors == 0))
	return bio;

Otherwise this patch looks good to me. Hence:

Reviewed-by: Bart Van Assche <bvanassche@....org>