get pages by template

$pages = get_pages(array(
 'meta_key' => '_wp_page_template',
 'meta_value' => 'page-product.php'
));
foreach($pages as $page){
 echo $page->post_title.'<br />';
}

======================= 

$args = array(
    'post_type'  => 'page', 
    'meta_query' => array( 
        array(
            'key'   => '_wp_page_template', 
            'value' => 'my_template.php'
        )
    )
);