alq_writen
return (alq_writen(alq, data, alq->aq_entlen, flags));
alq_writen(siftr_alq, sbuf_data(s), sbuf_len(s), ALQ_WAITOK);
alq_writen(siftr_alq, sbuf_data(s)+i, bytes_to_write, ALQ_WAITOK);
int alq_writen(struct alq *alq, void *data, int len, int flags);