Re: [PATCH v4 06/11] md: support to align bio to limits

在 2026/1/12 12:28, Yu Kuai 写道:
> For personalities that report optimal IO size, it indicates that users
> can get the best IO bandwidth if they issue IO with this size. However
> there is also an implicit condition that IO should also be aligned to the
> optimal IO size.
> 
> Currently, bio will only be split by limits, if bio offset is not aligned
> to limits, then all split bio will not be aligned. This patch add a new
> feature to align bio to limits first, and following patches will support
> this for each personality if necessary.
> 
> Link: https://lore.kernel.org/linux-raid/[email protected]
> Signed-off-by: Yu Kuai <[email protected]>
> Reviewed-by: Li Nan <[email protected]>
> ---
>   drivers/md/md.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
>   drivers/md/md.h |  2 ++
>   2 files changed, 56 insertions(+)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 21b0bc3088d2..731ec800f5cb 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -428,6 +428,56 @@ bool md_handle_request(struct mddev *mddev, struct bio *bio)
>   }
>   EXPORT_SYMBOL(md_handle_request);
>   
> +static struct bio *__md_bio_align_to_limits(struct mddev *mddev,
> +					     struct bio *bio)
> +{
> +	unsigned int max_sectors = mddev->gendisk->queue->limits.max_sectors;
> +	sector_t start = bio->bi_iter.bi_sector;
> +	sector_t end = start + bio_sectors(bio);
> +	sector_t align_start;
> +	sector_t align_end;
> +	u32 rem;
> +
> +	/* calculate align_start = roundup(start, max_sectors) */

Can we use roundup_u64() here?

> +	align_start = start;
> +	rem = sector_div(align_start, max_sectors);
> +	/* already aligned */
> +	if (!rem)
> +		return bio;
> +
> +	align_start = start + max_sectors - rem;
> +
> +	/* calculate align_end = rounddown(end, max_sectors) */

Use div64_u64_rem() here seems better.

> +	align_end = end;
> +	rem = sector_div(align_end, max_sectors);
> +	align_end = end - rem;
> +
> +	/* bio is too small to split */
> +	if (align_end <= align_start)
> +		return bio;
> +
> +	return bio_submit_split_bioset(bio, align_start - start,
> +				       &mddev->gendisk->bio_split);
> +}
> +
-- 
Thanks,
Nan