function redirect_logged_in_user()
{
    if( is_user_logged_in ) {
      wp_redirect('http://customurl');
    }
}

global $pagenow;
if( $pagenow == 'wp-login.php')
redirect_logged_in_user();

<?php
function daro_login_redirect( $redirect_to, $request, $user ) {
    //is there a user to check?
    if ( isset( $user->roles ) && is_array( $user->roles ) ) {
        //check for admins
        // edit this part accordingly to your login needs:
        // maybe you can skip the else statement
        if ( in_array( 'administrator', $user->roles ) ) {
            // redirect them to the default place
            return $redirect_to;
        } else {
            return home_url();
        }
    } else {
        return $redirect_to;
    }
}

add_filter( 'login_redirect', 'daro_login_redirect', 10, 3 );