new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/drivers/hid/hid-roccat.c b/drivers/hid/hid-roccat.c
index b685b04..d7437ef 100644
--- a/drivers/hid/hid-roccat.c
+++ b/drivers/hid/hid-roccat.c
@@ -378,7 +378,7 @@
 
 static long roccat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
-	struct inode *inode = file->f_path.dentry->d_inode;
+	struct inode *inode = file_inode(file);
 	struct roccat_device *device;
 	unsigned int minor = iminor(inode);
 	long retval = 0;