md: fix mssing blktrace bio split events

JIRA: https://issues.redhat.com/browse/RHEL-123668

commit 22f1662
Author: Yu Kuai <yukuai3@huawei.com>
Date:   Wed Sep 10 14:30:44 2025 +0800

    md: fix mssing blktrace bio split events

    If bio is split by internal handling like chunksize or badblocks, the
    corresponding trace_block_split() is missing, resulting in blktrace
    inability to catch BIO split events and making it harder to analyze the
    BIO sequence.

    Cc: stable@vger.kernel.org
    Fixes: 4b1faf9 ("block: Kill bio_pair_split()")
    Signed-off-by: Yu Kuai <yukuai3@huawei.com>
    Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Nigel Croxon <ncroxon@redhat.com>

Author: ncroxon

drivers/md/md-linear.c

@@ -266,6 +266,7 @@ static bool linear_make_request(struct mddev *mddev, struct bio *bio)
 		}
 
 		bio_chain(split, bio);
+		trace_block_split(split, bio->bi_iter.bi_sector);
 		submit_bio_noacct(bio);
 		bio = split;
 	}

drivers/md/raid0.c

@@ -472,7 +472,9 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 			bio_endio(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;
@@ -620,7 +622,9 @@ static bool raid0_make_request(struct mddev *mddev, struct bio *bio)
 			bio_endio(bio);
 			return true;
 		}
+
 		bio_chain(split, bio);
+		trace_block_split(split, bio->bi_iter.bi_sector);
 		raid0_map_submit_bio(mddev, bio);
 		bio = split;
 	}

drivers/md/raid1.c

@@ -1384,7 +1384,9 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
 			error = PTR_ERR(split);
 			goto err_handle;
 		}
+
 		bio_chain(split, bio);
+		trace_block_split(split, bio->bi_iter.bi_sector);
 		submit_bio_noacct(bio);
 		bio = split;
 		r1_bio->master_bio = bio;
@@ -1616,7 +1618,9 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 			error = PTR_ERR(split);
 			goto err_handle;
 		}
+
 		bio_chain(split, bio);
+		trace_block_split(split, bio->bi_iter.bi_sector);
 		submit_bio_noacct(bio);
 		bio = split;
 		r1_bio->master_bio = bio;

drivers/md/raid10.c

@@ -1209,7 +1209,9 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
 			error = PTR_ERR(split);
 			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);
@@ -1495,7 +1497,9 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 			error = PTR_ERR(split);
 			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);
@@ -1679,7 +1683,9 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 			bio_endio(bio);
 			return 0;
 		}
+
 		bio_chain(split, bio);
+		trace_block_split(split, bio->bi_iter.bi_sector);
 		allow_barrier(conf);
 		/* Resend the fist split part */
 		submit_bio_noacct(split);
@@ -1694,7 +1700,9 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 			bio_endio(bio);
 			return 0;
 		}
+
 		bio_chain(split, bio);
+		trace_block_split(split, bio->bi_iter.bi_sector);
 		allow_barrier(conf);
 		/* Resend the second split part */
 		submit_bio_noacct(bio);

drivers/md/raid5.c

@@ -5475,8 +5475,10 @@ static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
 
 	if (sectors < bio_sectors(raid_bio)) {
 		struct r5conf *conf = mddev->private;
+
 		split = bio_split(raid_bio, sectors, GFP_NOIO, &conf->bio_split);
 		bio_chain(split, raid_bio);
+		trace_block_split(split, raid_bio->bi_iter.bi_sector);
 		submit_bio_noacct(raid_bio);
 		raid_bio = split;
 	}