Auto reduce WooCommerce order stock at checkout

/**
* Auto reduce WooCommerce order stock at checkout.
* Add to theme functions.php file
*/

add_action( 'woocommerce_checkout_order_processed', 'woocommerce_reduce_order_stock' );
function woocommerce_reduce_order_stock( $order_id ) {
    global $woocommerce;

    if ( !$order_id )
        return;
    $order = new WC_Order( $order_id );
    $order->reduce_order_stock();
}

add_filter( 'woocommerce_payment_complete_reduce_order_stock', '__return_false' ); /** reduce stock just once */