Put explicit lock_kernel() calls into raw_open(), even though the existing
locking looks adequate.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 
 #include <asm/uaccess.h>
 
                return 0;
        }
 
+       lock_kernel();
        mutex_lock(&raw_mutex);
 
        /*
                        bdev->bd_inode->i_mapping;
        filp->private_data = bdev;
        mutex_unlock(&raw_mutex);
+       unlock_kernel();
        return 0;
 
 out2: