[PATCH RFC v2 04/10] md/raid10: convert read/write to use bio_submit_split_bioset()

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

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 drivers/md/raid10.c | 51 +++++++++++++++++++--------------------------
 drivers/md/raid10.h |  2 ++
 2 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index b60c30bfb6c7..0e7d2a67fca6 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 +1204,15 @@ 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);
-			goto err_handle;
-		}
-		bio_chain(split, bio);
 		allow_barrier(conf);
-		submit_bio_noacct(bio);
+		bio = bio_submit_split_bioset(bio, max_sectors,
+					      &conf->bio_split);
 		wait_barrier(conf, false);
-		bio = split;
+		if (!bio) {
+			set_bit(R10BIO_Returned, &r10_bio->state);
+			goto err_handle;
+		}
+
 		r10_bio->master_bio = bio;
 		r10_bio->sectors = max_sectors;
 	}
@@ -1239,10 +1238,9 @@ 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 +1349,6 @@ 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 +1462,8 @@ 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 +1484,15 @@ 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);
-			goto err_handle;
-		}
-		bio_chain(split, bio);
 		allow_barrier(conf);
-		submit_bio_noacct(bio);
+		bio = bio_submit_split_bioset(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;
+		}
+
 		r10_bio->master_bio = bio;
 	}
 
@@ -1531,8 +1524,6 @@ 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..ba13f08a2646 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -165,6 +165,8 @@ enum r10bio_state {
  * so that raid10d knows what to do with them.
  */
 	R10BIO_ReadError,
+/* For bio_split errors, record that bi_end_io was called */
+	R10BIO_Returned,
 /* If a write for this request means we can clear some
  * known-bad-block records, we set this flag.
  */
-- 
2.39.2