Re: [PATCH v2 06/11] md: support to align bio to limits

在 2026/1/3 23:45, Yu Kuai 写道:
> For personalities that report optimal IO size, it's indicate 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.
> 
> Signed-off-by: Yu Kuai <[email protected]>
> ---
>   drivers/md/md.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>   drivers/md/md.h |  2 ++
>   2 files changed, 48 insertions(+)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 21b0bc3088d2..7292aedef01b 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -428,6 +428,48 @@ 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 align_start = roundup(start, max_sectors);
> +	sector_t end;
> +	sector_t align_end;
> +
> +	/* already aligned */
> +	if (align_start == start)
> +		return bio;
> +
> +	end = start + bio_sectors(bio);
> +	align_end = rounddown(end, max_sectors);
> +
> +	/* 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);
> +}
> +
> +static struct bio *md_bio_align_to_limits(struct mddev *mddev, struct bio *bio)
> +{
> +	if (!test_bit(MD_BIO_ALIGN, &mddev->flags))
> +		return bio;
> +
> +	/* atomic write can't split */
> +	if (bio->bi_opf & REQ_ATOMIC)
> +		return bio;
> +
> +	switch (bio_op(bio)) {
> +	case REQ_OP_READ:
> +	case REQ_OP_WRITE:
> +		return __md_bio_align_to_limits(mddev, bio);
> +	default:
> +		return bio;
> +	}
> +}
> +
>   static void md_submit_bio(struct bio *bio)
>   {
>   	const int rw = bio_data_dir(bio);
> @@ -443,6 +485,10 @@ static void md_submit_bio(struct bio *bio)
>   		return;
>   	}
>   
> +	bio = md_bio_align_to_limits(mddev, bio);
> +	if (!bio)
> +		return;
> +
>   	bio = bio_split_to_limits(bio);
>   	if (!bio)
>   		return;
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index b8c5dec12b62..e7aba83b708b 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -347,6 +347,7 @@ struct md_cluster_operations;
>    * @MD_HAS_SUPERBLOCK: There is persistence sb in member disks.
>    * @MD_FAILLAST_DEV: Allow last rdev to be removed.
>    * @MD_SERIALIZE_POLICY: Enforce write IO is not reordered, just used by raid1.
> + * @MD_BIO_ALIGN: Bio issued to the array will align to io_opt before split.
>    *
>    * change UNSUPPORTED_MDDEV_FLAGS for each array type if new flag is added
>    */
> @@ -366,6 +367,7 @@ enum mddev_flags {
>   	MD_HAS_SUPERBLOCK,
>   	MD_FAILLAST_DEV,
>   	MD_SERIALIZE_POLICY,
> +	MD_BIO_ALIGN,
>   };
>   
>   enum mddev_sb_flags {

LGTM

Reviewed-by: Li Nan <[email protected]>

-- 
Thanks,
Nan