new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index f946ca7..05dfd56 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -852,7 +852,7 @@
 			const char __user *userbuf,
 			size_t count, loff_t *pos)
 {
-	struct ibm_struct *ibm = PDE(file->f_path.dentry->d_inode)->data;
+	struct ibm_struct *ibm = PDE(file_inode(file))->data;
 	char *kernbuf;
 	int ret;