ovl: fix nlink leak in ovl_rename()

This patch fixes an overlay inode nlink leak in the case where
ovl_rename() renames over a non-dir.

This is not so critical, because overlay inode doesn't rely on
nlink dropping to zero for inode deletion.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/dir.c

@@ -1046,6 +1046,13 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 	if (cleanup_whiteout)
 		ovl_cleanup(old_upperdir->d_inode, newdentry);
 
+	if (overwrite && d_inode(new)) {
+		if (new_is_dir)
+			clear_nlink(d_inode(new));
+		else
+			drop_nlink(d_inode(new));
+	}
+
 	ovl_dentry_version_inc(old->d_parent);
 	ovl_dentry_version_inc(new->d_parent);