WP maintenance page redirect function

maintenance_redirect.php

/***** MAINTENANCE *****/
//* Redirect for temp landing page
add_action( 'template_redirect', 'gum_redirect_maintenance_page' );
function gum_redirect_maintenance_page() {
	$redirect = FALSE;
	$page = home_url( '/maintenance/' ); //slug for wp page
		
	if ( $redirect && !is_user_logged_in() && trim( $_SERVER['REQUEST_URI'], '/' ) != 'maintenance' && $_SERVER['REQUEST_URI'] != '/wp-admin/' ) :
		wp_redirect( $page ); 
		exit;
			
	endif;
}