md: use part_[begin|end]_io_acct instead of disk_[begin|end]_io_acct

This enables proper statistics in /proc/diskstats for md partitions.
Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/md.c

@@ -464,6 +464,7 @@ struct md_io {
 	bio_end_io_t *orig_bi_end_io;
 	void *orig_bi_private;
 	unsigned long start_time;
+	struct hd_struct *part;
 };
 
 static void md_end_io(struct bio *bio)
@@ -471,7 +472,7 @@ static void md_end_io(struct bio *bio)
 	struct md_io *md_io = bio->bi_private;
 	struct mddev *mddev = md_io->mddev;
 
-	disk_end_io_acct(mddev->gendisk, bio_op(bio), md_io->start_time);
+	part_end_io_acct(md_io->part, bio, md_io->start_time);
 
 	bio->bi_end_io = md_io->orig_bi_end_io;
 	bio->bi_private = md_io->orig_bi_private;
@@ -517,9 +518,8 @@ static blk_qc_t md_submit_bio(struct bio *bio)
 		bio->bi_end_io = md_end_io;
 		bio->bi_private = md_io;
 
-		md_io->start_time = disk_start_io_acct(mddev->gendisk,
-						       bio_sectors(bio),
-						       bio_op(bio));
+		md_io->start_time = part_start_io_acct(mddev->gendisk,
+						       &md_io->part, bio);
 	}
 
 	/* bio could be mergeable after passing to underlayer */