+	if (!vec)
+		ret = blk_rq_map_user(q, req, NULL, ubuffer, bufflen,
+			GFP_KERNEL);
+	else {
+		struct iovec fast_iov[UIO_FASTIOV];
+		struct iovec *iov = fast_iov;
+		struct iov_iter iter;
+
+		ret = import_iovec(rq_data_dir(req), ubuffer, bufflen,
+				UIO_FASTIOV, &iov, &iter);
+		if (ret < 0)
 			goto out;
+
+		ret = blk_rq_map_user_iov(q, req, NULL, &iter, GFP_KERNEL);
+		kfree(iov);
+	}

As mentioned before this is something that should got into blk-map.c
as a separate helper, and scsi_ioctl.c and sg.c should be switched to
use it as well.

Otherwise this looks good.