[PATCH RFC 4/7] md/raid10: convert read/write to use bio_submit_split()

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

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 discard is not handled, because discard is only splited for
unaligned head and tail.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/raid10.c | 53 ++++++++++++++++++++-------------------------
 drivers/md/raid10.h |  1 +
 2 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index b60c30bfb6c7..b8777661307b 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -322,10 +322,12 @@ static void raid_end_bio_io(struct r10bio *r10_bio)
 	struct bio *bio = r10_bio->master_bio;
 	struct r10conf *conf = r10_bio->mddev->private;
 
-	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
-		bio->bi_status = BLK_STS_IOERR;
+	if (!test_and_set_bit(R10BIO_Returned, &r10_bio->state)) {
+		if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
+			bio->bi_status = BLK_STS_IOERR;
+		bio_endio(bio);
+	}
 
-	bio_endio(bio);
 	/*
 	 * Wake up any possible resync thread that waits for the device
 	 * to go idle.
@@ -1154,7 +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) {
 		/*
@@ -1203,17 +1204,16 @@ 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);
-			goto err_handle;
-		}
-		bio_chain(split, bio);
 		allow_barrier(conf);
-		submit_bio_noacct(bio);
+		bio = bio_submit_split(bio, max_sectors, &conf->bio_split);
 		wait_barrier(conf, false);
-		bio = split;
+
+		if (!bio) {
+			set_bit(R10BIO_Returned, &r10_bio->state);
+			goto err_handle;
+		}
+
+		bio->bi_opf &= ~REQ_NOMERGE;
 		r10_bio->master_bio = bio;
 		r10_bio->sectors = max_sectors;
 	}
@@ -1239,10 +1239,9 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
 	mddev_trace_remap(mddev, read_bio, r10_bio->sector);
 	submit_bio_noacct(read_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);
 }
 
@@ -1351,7 +1350,6 @@ 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,
@@ -1465,10 +1463,8 @@ 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)
@@ -1489,17 +1485,16 @@ 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);
-			goto err_handle;
-		}
-		bio_chain(split, bio);
 		allow_barrier(conf);
-		submit_bio_noacct(bio);
+		bio = bio_submit_split(bio, r10_bio->sectors, &conf->bio_split);
 		wait_barrier(conf, false);
-		bio = split;
+
+		if (!bio) {
+			set_bit(R10BIO_Returned, &r10_bio->state);
+			goto err_handle;
+		}
+
+		bio->bi_opf &= ~REQ_NOMERGE;
 		r10_bio->master_bio = bio;
 	}
 
@@ -1531,8 +1526,6 @@ 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);
 }
 
diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index 3f16ad6904a9..cc167e708125 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -165,6 +165,7 @@ enum r10bio_state {
  * so that raid10d knows what to do with them.
  */
 	R10BIO_ReadError,
+	R10BIO_Returned,
 /* If a write for this request means we can clear some
  * known-bad-block records, we set this flag.
  */
-- 
2.39.2