md/md-multipath: enable io accounting

use md_account_bio() to enable io accounting, also make sure
mddev_suspend() will wait for all io to be done.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230621165110.1498313-7-yukuai1@huaweicloud.com

drivers/md/md-multipath.c

@@ -107,6 +107,7 @@ static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
 	    && md_flush_request(mddev, bio))
 		return true;
 
+	md_account_bio(mddev, &bio);
 	mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
 
 	mp_bh->master_bio = bio;