[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>

1 files changed, 8 insertions, 14 deletions

diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
index 2f419b0ea628..af616aeaa938 100644
--- a/drivers/s390/char/vmcp.c
+++ b/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