new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/drivers/usb/gadget/storage_common.c b/drivers/usb/gadget/storage_common.c
index 0e3ae43..b5d3f0e 100644
--- a/drivers/usb/gadget/storage_common.c
+++ b/drivers/usb/gadget/storage_common.c
@@ -501,7 +501,7 @@
 	if (!(filp->f_mode & FMODE_WRITE))
 		ro = 1;
 
-	inode = filp->f_path.dentry->d_inode;
+	inode = file_inode(filp);
 	if ((!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))) {
 		LINFO(curlun, "invalid file type: %s\n", filename);
 		goto out;