func readDirFn(dirPath string, fn func(name string, typ os.FileMode) error) error {
	fd, err := openFileWithFD(dirPath, readMode, 0o666)
	if err != nil {
		if osErrToFileErr(err) == errFileNotFound {
			return nil
		}
		if !osIsPermission(err) {
			return osErrToFileErr(err)
		}
		// There may be permission error when dirPath
		// is at the root of the disk mount that may
		// not have the permissions to avoid 'noatime'