new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/kernel/sys.c b/kernel/sys.c
index 265b376..e3932ea 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1792,14 +1792,14 @@
 static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
 {
 	struct fd exe;
-	struct dentry *dentry;
+	struct inode *inode;
 	int err;
 
 	exe = fdget(fd);
 	if (!exe.file)
 		return -EBADF;
 
-	dentry = exe.file->f_path.dentry;
+	inode = file_inode(exe.file);
 
 	/*
 	 * Because the original mm->exe_file points to executable file, make
@@ -1807,11 +1807,11 @@
 	 * overall picture.
 	 */
 	err = -EACCES;
-	if (!S_ISREG(dentry->d_inode->i_mode)	||
+	if (!S_ISREG(inode->i_mode)	||
 	    exe.file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 		goto exit;
 
-	err = inode_permission(dentry->d_inode, MAY_EXEC);
+	err = inode_permission(inode, MAY_EXEC);
 	if (err)
 		goto exit;