md/raid1: switch to use md_account_bio() for io accounting

Two problems can be fixed this way:

1) 'active_io' will represent inflight io instead of io that is
dispatching.

2) If io accounting is enabled or disabled while io is still inflight,
bio_start_io_acct() and bio_end_io_acct() is not balanced and io
inflight counter will be leaked.

Signed-off-by: Yu Kuai <[e-mail]>
Reviewed-by: Xiao Ni <[e-mail]>
Signed-off-by: Song Liu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/md/raid1.c

···
 	if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
 		bio->bi_status = BLK_STS_IOERR;
 
-	if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
-		bio_end_io_acct(bio, r1_bio->start_time);
 	bio_endio(bio);
 }
 
···
 	}
 
 	r1_bio->read_disk = rdisk;
-
-	if (!r1bio_existed && blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
-		r1_bio->start_time = bio_start_io_acct(bio);
-
+	if (!r1bio_existed) {
+		md_account_bio(mddev, &bio);
+		r1_bio->master_bio = bio;
+	}
 	read_bio = bio_alloc_clone(mirror->rdev->bdev, bio, gfp,
 				   &mddev->bio_set);
 
···
 		r1_bio->sectors = max_sectors;
 	}
 
-	if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
-		r1_bio->start_time = bio_start_io_acct(bio);
+	md_account_bio(mddev, &bio);
+	r1_bio->master_bio = bio;
 	atomic_set(&r1_bio->remaining, 1);
 	atomic_set(&r1_bio->behind_remaining, 0);
 

drivers/md/raid1.h

···
 	sector_t		sector;
 	int			sectors;
 	unsigned long		state;
-	unsigned long		start_time;
 	struct mddev		*mddev;
 	/*
 	 * original bio going to /dev/mdx