What is the optimal way to filter out subpages from admin?

This works for our needs:

# Parent filtering
function wps_restrict_manage_posts() {
    global $typenow;

    # only run this filter on page post type
    if ( $typenow == 'konverentsid' ) {
        # Parent Page Filter (HTML)
        $args = array(
            'post_type' => 'konverentsid',
            'child_of' => 0,
            'show_option_none' => __('Show all pages'),
            'depth' => 1,
            'name' => 'wps_page_filter',
            'selected' => $_GET['wps_page_filter'],
        );
        $dropdown = wp_dropdown_pages( $args );
    }

}
add_action ( 'restrict_manage_posts' , 'wps_restrict_manage_posts' );

# Add an option to show top level pages only
add_filter ( 'wp_dropdown_pages' , 'wps_insert_option_in_dropdown' );
function wps_insert_option_in_dropdown ( $output ) {
    $filter = $_GET['wps_page_filter'];
    if ( $filter == 'parent' )
        $selected = ' selected="selected"';
    else
        $selected = '';
    $second_option = __("Show all pages") . '</option><option value="parent"' . $selected . '>' . __("Parent Pages Only") . '</option>';
    return preg_replace( '#Show all pages</option>#' , $second_option , $output );
}
add_filter ( 'parse_query', 'wps_admin_posts_filter' );

function wps_admin_posts_filter( $query ) {
    global $pagenow;

    # Change query based on post_parent
    $wps_page_filter = $_GET['wps_page_filter'];
    if ( is_admin() && $pagenow == 'edit.php' && !empty( $wps_page_filter ) ) {
        if ( $wps_page_filter == 'parent' )
            $query->query_vars['post_parent'] = 0;
        else
            $query->query_vars['post_parent'] = $wps_page_filter;
    }
}