Re: [PATCH 1/3] block: add a bio_reuse helper

Hans Holmberg
2025-12-19T07:45:15Z

On 18/12/2025 07:32, Christoph Hellwig wrote:
> Add a helper to allow an existing bio to be resubmitted withtout
> having to re-add the payload.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> block/bio.c | 25 +++++++++++++++++++++++++
> include/linux/bio.h | 1 +
> 2 files changed, 26 insertions(+)
>
> diff --git a/block/bio.c b/block/bio.c
> index e726c0e280a8..1b68ae877468 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -311,6 +311,31 @@ void bio_reset(struct bio *bio, struct block_device *bdev, blk_opf_t opf)
> }
> EXPORT_SYMBOL(bio_reset);
>
> +/**
> + * bio_reuse - reuse a bio with the payload left intact
> + * @bio bio to reuse
> + *
> + * Allow reusing an existing bio for another operation with all set up
> + * fields including the payload, device and end_io handler left intact.
> + *
> + * Typically used for bios first used to read data which is then written
> + * to another location without modification.
> + */
> +void bio_reuse(struct bio *bio)
> +{
> + unsigned short vcnt = bio->bi_vcnt, i;
> + bio_end_io_t *end_io = bio->bi_end_io;
> + void *private = bio->bi_private;
> +
> + bio_reset(bio, bio->bi_bdev, bio->bi_opf);
> + for (i = 0; i < vcnt; i++)
> + bio->bi_iter.bi_size += bio->bi_io_vec[i].bv_len;
> + bio->bi_vcnt = vcnt;
> + bio->bi_private = private;
> + bio->bi_end_io = end_io;
> +}
> +EXPORT_SYMBOL_GPL(bio_reuse);
> +
> static struct bio *__bio_chain_endio(struct bio *bio)
> {
> struct bio *parent = bio->bi_private;
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index ad2d57908c1c..c0190f8badde 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -414,6 +414,7 @@ static inline void bio_init_inline(struct bio *bio, struct block_device *bdev,
> }
> extern void bio_uninit(struct bio *);
> void bio_reset(struct bio *bio, struct block_device *bdev, blk_opf_t opf);
> +void bio_reuse(struct bio *bio);
> void bio_chain(struct bio *, struct bio *);
>
> int __must_check bio_add_page(struct bio *bio, struct page *page, unsigned len,

Looks good to me,

Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>