[PATCH RFC 2/7] md/raid0: convert raid0_handle_discard() to use bio_submit_split()

[Yu Kuai <yukuai1@huaweicloud.com>]

From: Yu Kuai <yukuai3@huawei.com>

On the one hand unify bio split code, prepare to fix disordered split
IO; On the other hand fix missing blkcg_bio_issue_init() and
trace_block_split() for split IO.

Noted raid0_make_request() already fix disordered split IO by
319ff40a5427 ("md/raid0: Fix performance regression for large sequential
writes"), by convert 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 | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index f1d8811a542a..19b5faf238b7 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -463,21 +463,17 @@ 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(bio,
+				zone->zone_end - bio->bi_iter.bi_sector,
+				&mddev->bio_set);
+		if (!bio)
 			return;
-		}
-		bio_chain(split, bio);
-		submit_bio_noacct(bio);
-		bio = split;
+
+		bio->bi_opf &= ~REQ_NOMERGE;
 		end = zone->zone_end;
-	} else
+	} else {
 		end = bio_end_sector(bio);
+	}
 
 	orig_end = end;
 	if (zone != conf->strip_zone)
-- 
2.39.2