AQ_WANTED
alq->aq_flags |= AQ_WANTED;
if (alq->aq_flags & AQ_WANTED) {
alq->aq_flags &= ~AQ_WANTED;
alq->aq_flags |= AQ_WANTED;
alq->aq_freebytes < len && !(alq->aq_flags & AQ_WANTED))
alq->aq_flags |= AQ_WANTED;
contigbytes < len && !(alq->aq_flags & AQ_WANTED))