void pdu_free(V9fsPDU *pdu)
{
    if (pdu) {
        V9fsState *s = pdu->s;
        /*
         * Cancelled pdu are added back to the freelist
         * by flush request .
         */
        if (!pdu->cancelled) {
            QLIST_REMOVE(pdu, next);
            QLIST_INSERT_HEAD(&s->free_list, pdu, next);
        }
    }
}
void pdu_free(V9fsPDU *pdu)
{
    if (pdu) {
        V9fsState *s = pdu->s;
         
        if (!pdu->cancelled) {
            QLIST_REMOVE(pdu, next);
            QLIST_INSERT_HEAD(&s->free_list, pdu, next);
        }
    }
}