linux-kernel - [PATCH v2 for-6.18/block 10/16] md/raid10: convert read/write to use bio_submit_split

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Message-Id: <20250910063056.4159857-11-yukuai1@huaweicloud.com>
Date: Wed, 10 Sep 2025 14:30:50 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: axboe@...nel.dk,
	hch@...radead.org,
	colyli@...nel.org,
	hare@...e.de,
	dlemoal@...nel.org,
	tieren@...as.com,
	bvanassche@....org,
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	satyat@...gle.com,
	ebiggers@...gle.com,
	kmo@...erainc.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: [PATCH v2 for-6.18/block 10/16] md/raid10: convert read/write to use bio_submit_split_bioset()

From: Yu Kuai <yukuai3@...wei.com>

Unify bio split code, prepare to fix ordering of split IO, the error path
is modified a bit, however no functional changes are intended:

- bio_submit_split_bioset() can fail the original bio directly
  by split error, set R10BIO_Uptodate in this case to notify
  raid_end_bio_io() that the original bio is returned already.
- set R10BIO_Uptodate and set error value to -EIO is useless now,
  for r10_bio without R10BIO_Uptodate, -EIO will be returned for
  original bio.

And discard is not handled, because discard is only split for
unaligned head and tail, and this can be considered slow path, the
reorder here does not matter much.

Signed-off-by: Yu Kuai <yukuai3@...wei.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 drivers/md/raid10.c | 42 +++++++++++++-----------------------------
 1 file changed, 13 insertions(+), 29 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index cac5c6df75bb..8996fa0dff60 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1156,7 +1156,6 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
 	int slot = r10_bio->read_slot;
 	struct md_rdev *err_rdev = NULL;
 	gfp_t gfp = GFP_NOIO;
-	int error;
 
 	if (slot >= 0 && r10_bio->devs[slot].rdev) {
 		/*
@@ -1205,19 +1204,15 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
 				   rdev->bdev,
 				   (unsigned long long)r10_bio->sector);
 	if (max_sectors < bio_sectors(bio)) {
-		struct bio *split = bio_split(bio, max_sectors,
-					      gfp, &conf->bio_split);
-		if (IS_ERR(split)) {
-			error = PTR_ERR(split);
+		allow_barrier(conf);
+		bio = bio_submit_split_bioset(bio, max_sectors,
+					      &conf->bio_split);
+		wait_barrier(conf, false);
+		if (!bio) {
+			set_bit(R10BIO_Returned, &r10_bio->state);
 			goto err_handle;
 		}
 
-		bio_chain(split, bio);
-		trace_block_split(split, bio->bi_iter.bi_sector);
-		allow_barrier(conf);
-		submit_bio_noacct(bio);
-		wait_barrier(conf, false);
-		bio = split;
 		r10_bio->master_bio = bio;
 		r10_bio->sectors = max_sectors;
 	}
@@ -1245,8 +1240,6 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
 	return;
 err_handle:
 	atomic_dec(&rdev->nr_pending);
-	bio->bi_status = errno_to_blk_status(error);
-	set_bit(R10BIO_Uptodate, &r10_bio->state);
 	raid_end_bio_io(r10_bio);
 }
 
@@ -1355,7 +1348,6 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 	int i, k;
 	sector_t sectors;
 	int max_sectors;
-	int error;
 
 	if ((mddev_is_clustered(mddev) &&
 	     mddev->cluster_ops->area_resyncing(mddev, WRITE,
@@ -1469,10 +1461,8 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 				 * complexity of supporting that is not worth
 				 * the benefit.
 				 */
-				if (bio->bi_opf & REQ_ATOMIC) {
-					error = -EIO;
+				if (bio->bi_opf & REQ_ATOMIC)
 					goto err_handle;
-				}
 
 				good_sectors = first_bad - dev_sector;
 				if (good_sectors < max_sectors)
@@ -1493,19 +1483,15 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 		r10_bio->sectors = max_sectors;
 
 	if (r10_bio->sectors < bio_sectors(bio)) {
-		struct bio *split = bio_split(bio, r10_bio->sectors,
-					      GFP_NOIO, &conf->bio_split);
-		if (IS_ERR(split)) {
-			error = PTR_ERR(split);
+		allow_barrier(conf);
+		bio = bio_submit_split_bioset(bio, r10_bio->sectors,
+					      &conf->bio_split);
+		wait_barrier(conf, false);
+		if (!bio) {
+			set_bit(R10BIO_Returned, &r10_bio->state);
 			goto err_handle;
 		}
 
-		bio_chain(split, bio);
-		trace_block_split(split, bio->bi_iter.bi_sector);
-		allow_barrier(conf);
-		submit_bio_noacct(bio);
-		wait_barrier(conf, false);
-		bio = split;
 		r10_bio->master_bio = bio;
 	}
 
@@ -1537,8 +1523,6 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 		}
 	}
 
-	bio->bi_status = errno_to_blk_status(error);
-	set_bit(R10BIO_Uptodate, &r10_bio->state);
 	raid_end_bio_io(r10_bio);
 }
 
-- 
2.39.2