[S390] s390/vmcp: use simple_read_from_buffer()

static ssize_t

vmcp_read(struct file *file, char __user *buff, size_t count, loff_t *ppos)

{

	size_t tocopy;

	ssize_t ret;

	size_t size;

	struct vmcp_session *session;

	session = (struct vmcp_session *)file->private_data;

	session = file->private_data;

	if (mutex_lock_interruptible(&session->mutex))

		return -ERESTARTSYS;

	if (!session->response) {

		mutex_unlock(&session->mutex);

		return 0;

	}

	if (*ppos > session->resp_size) {

		mutex_unlock(&session->mutex);

		return 0;

	}

	tocopy = min(session->resp_size - (size_t) (*ppos), count);

	tocopy = min(tocopy, session->bufsize - (size_t) (*ppos));

	size = min_t(size_t, session->resp_size, session->bufsize);

	ret = simple_read_from_buffer(buff, count, ppos,

					session->response, size);

	if (copy_to_user(buff, session->response + (*ppos), tocopy)) {

	mutex_unlock(&session->mutex);

		return -EFAULT;

	}

	mutex_unlock(&session->mutex);

	*ppos += tocopy;

	return tocopy;

	return ret;

}

static ssize_t