[S390] s390/vmcp: use simple_read_from_buffer()

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/vmcp.c

@@ -61,30 +61,24 @@ static int vmcp_release(struct inode *inode, struct file *file)
 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