Parent path means the parent directory for the path.
   * Ancestor path means the last (the closest) existing ancestor directory
   * of the path.
   * Note that if the parent path exists,
   * then the parent path and the ancestor path are the same.
Parent path means the parent directory for the path.
   * Ancestor path means the last (the closest) existing ancestor directory
   * of the path.
   * Note that if the parent path exists,
   * then the parent path and the ancestor path are the same. | FSPermissionChecker.java