md/raid1: convert to use bio_submit_split_bioset()

Unify bio split code, and prepare to fix ordering of split IO.

Noted that bio_submit_split_bioset() can fail the original bio directly
by split error, set R1BIO_Returned in this case to notify raid_end_bio_io()
that the original bio is returned already.

Signed-off-by: Yu Kuai <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/md/raid1.c

···
 	struct raid1_info *mirror;
 	struct bio *read_bio;
 	int max_sectors;
-	int rdisk, error;
+	int rdisk;
 	bool r1bio_existed = !!r1_bio;
 
 	/*
···
 	}
 
 	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);
+		bio = bio_submit_split_bioset(bio, max_sectors,
+					      &conf->bio_split);
+		if (!bio) {
+			set_bit(R1BIO_Returned, &r1_bio->state);
 			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;
 		r1_bio->sectors = max_sectors;
 	}
···
 
 err_handle:
 	atomic_dec(&mirror->rdev->nr_pending);
-	bio->bi_status = errno_to_blk_status(error);
-	set_bit(R1BIO_Uptodate, &r1_bio->state);
 	raid_end_bio_io(r1_bio);
 }
 
···
 {
 	struct r1conf *conf = mddev->private;
 	struct r1bio *r1_bio;
-	int i, disks, k, error;
+	int i, disks, k;
 	unsigned long flags;
 	int first_clone;
 	int max_sectors;
···
 				 * 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 - r1_bio->sector;
 				if (good_sectors < max_sectors)
···
 		max_sectors = min_t(int, max_sectors,
 				    BIO_MAX_VECS * (PAGE_SIZE >> 9));
 	if (max_sectors < bio_sectors(bio)) {
-		struct bio *split = bio_split(bio, max_sectors,
-					      GFP_NOIO, &conf->bio_split);
-
-		if (IS_ERR(split)) {
-			error = PTR_ERR(split);
+		bio = bio_submit_split_bioset(bio, max_sectors,
+					      &conf->bio_split);
+		if (!bio) {
+			set_bit(R1BIO_Returned, &r1_bio->state);
 			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;
 		r1_bio->sectors = max_sectors;
 	}
···
 		}
 	}
 
-	bio->bi_status = errno_to_blk_status(error);
-	set_bit(R1BIO_Uptodate, &r1_bio->state);
 	raid_end_bio_io(r1_bio);
 }
 

drivers/md/raid1.h

···
  * any write was successful.  Otherwise we call when
  * any write-behind write succeeds, otherwise we call
  * with failure when last write completes (and all failed).
- * Record that bi_end_io was called with this flag...
+ *
+ * And for bio_split errors, record that bi_end_io was called
+ * with this flag...
  */
 	R1BIO_Returned,
 /* If a write for this request means we can clear some