1 files changed, 17 insertions, 24 deletions

diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
index 2f419b0ea628..09e7d9bf438b 100644
--- a/drivers/s390/char/vmcp.c
+++ b/drivers/s390/char/vmcp.c
@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/miscdevice.h>
 #include <linux/module.h>
+#include <linux/smp_lock.h>
 #include <asm/cpcmd.h>
 #include <asm/debug.h>
 #include <asm/uaccess.h>
@@ -39,11 +40,14 @@ static int vmcp_open(struct inode *inode, struct file *file)
         session = kmalloc(sizeof(*session), GFP_KERNEL);
         if (!session)
                 return -ENOMEM;
+
+        lock_kernel();
         session->bufsize = PAGE_SIZE;
         session->response = NULL;
         session->resp_size = 0;
         mutex_init(&session->mutex);
         file->private_data = session;
+        unlock_kernel();
         return nonseekable_open(inode, file);
 }
 
@@ -61,30 +65,24 @@ 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
@@ -198,27 +196,23 @@ static int __init vmcp_init(void)
                 PRINT_WARN("z/VM CP interface is only available under z/VM\n");
                 return -ENODEV;
         }
+
         vmcp_debug = debug_register("vmcp", 1, 1, 240);
-        if (!vmcp_debug) {
-                PRINT_ERR("z/VM CP interface not loaded. Could not register "
-                           "debug feature\n");
+        if (!vmcp_debug)
                 return -ENOMEM;
-        }
+
         ret = debug_register_view(vmcp_debug, &debug_hex_ascii_view);
         if (ret) {
-                PRINT_ERR("z/VM CP interface not loaded. Could not register "
-                          "debug feature view. Error code: %d\n", ret);
                 debug_unregister(vmcp_debug);
                 return ret;
         }
+
         ret = misc_register(&vmcp_dev);
         if (ret) {
-                PRINT_ERR("z/VM CP interface not loaded. Could not register "
-                           "misc device. Error code: %d\n", ret);
                 debug_unregister(vmcp_debug);
                 return ret;
         }
-        PRINT_INFO("z/VM CP interface loaded\n");
+
         return 0;
 }
 
@@ -226,7 +220,6 @@ static void __exit vmcp_exit(void)
 {
         misc_deregister(&vmcp_dev);
         debug_unregister(vmcp_debug);
-        PRINT_INFO("z/VM CP interface unloaded.\n");
 }
 
 module_init(vmcp_init);