From: Yu Kuai <yukuai3@huawei.com>

Unify bio split code, and prepare to fix disordered split IO

Noted commit 319ff40a5427 ("md/raid0: Fix performance regression for large
sequential writes") already fix disordered split IO by converting bio to
underlying disks before submit_bio_noacct(), with the respect
md_submit_bio() already split by sectors, and raid0_make_request() will
split at most once for unaligned IO. This is a bit hacky and we'll convert
this to solution in general later.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 drivers/md/raid0.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 1ba7d0c090f7..99f7839b4e96 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -463,23 +463,16 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 	zone = find_zone(conf, &start);
 
 	if (bio_end_sector(bio) > zone->zone_end) {
-		struct bio *split = bio_split(bio,
-			zone->zone_end - bio->bi_iter.bi_sector, GFP_NOIO,
-			&mddev->bio_set);
-
-		if (IS_ERR(split)) {
-			bio->bi_status = errno_to_blk_status(PTR_ERR(split));
-			bio_endio(bio);
+		bio = bio_submit_split_bioset(
+				bio, zone->zone_end - bio->bi_iter.bi_sector,
+				&mddev->bio_set);
+		if (!bio)
 			return;
-		}
 
-		bio_chain(split, bio);
-		trace_block_split(split, bio->bi_iter.bi_sector);
-		submit_bio_noacct(bio);
-		bio = split;
 		end = zone->zone_end;
-	} else
+	} else {
 		end = bio_end_sector(bio);
+	}
 
 	orig_end = end;
 	if (zone != conf->strip_zone)
-- 
2.39.2

On Mon, Sep 01, 2025 at 11:32:11AM +0800, Yu Kuai wrote:
> +		bio = bio_submit_split_bioset(
> +				bio, zone->zone_end - bio->bi_iter.bi_sector,
> +				&mddev->bio_set);

Nit: this would be a bit more readable as:

		bio = bio_submit_split_bioset(bio,
				zone->zone_end - bio->bi_iter.bi_sector,
				&mddev->bio_set);

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

On 9/1/25 12:32 PM, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> Unify bio split code, and prepare to fix disordered split IO

Missing the period at the end of the above sentence.

> 
> Noted commit 319ff40a5427 ("md/raid0: Fix performance regression for large
> sequential writes") already fix disordered split IO by converting bio to
> underlying disks before submit_bio_noacct(), with the respect
> md_submit_bio() already split by sectors, and raid0_make_request() will
> split at most once for unaligned IO. This is a bit hacky and we'll convert
> this to solution in general later.

I do not see how this is relevant to this patch. The patch is a simple
straightforward conversion of hard-coded BIO split to using
bio_submit_split_bioset(). So I would just say that.

> Signed-off-by: Yu Kuai <yukuai3@huawei.com>

With the above addressed, this looks OK to me.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research

Hi,

在 2025/09/01 14:37, Damien Le Moal 写道:
> On 9/1/25 12:32 PM, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> Unify bio split code, and prepare to fix disordered split IO
> 
> Missing the period at the end of the above sentence.
> 
>>
>> Noted commit 319ff40a5427 ("md/raid0: Fix performance regression for large
>> sequential writes") already fix disordered split IO by converting bio to
>> underlying disks before submit_bio_noacct(), with the respect
>> md_submit_bio() already split by sectors, and raid0_make_request() will
>> split at most once for unaligned IO. This is a bit hacky and we'll convert
>> this to solution in general later.
> 
> I do not see how this is relevant to this patch. The patch is a simple
> straightforward conversion of hard-coded BIO split to using
> bio_submit_split_bioset(). So I would just say that.

This is just a note that why bio_split() from read/write is not
converted now, because disordered problem is fixed by above commit
already.

Later patch 15 will convert bio_split() from read/write.
> 
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> 
> With the above addressed, this looks OK to me.
> 
> Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
> 

Thanks,
Kuai