@@ -1070,7 +1070,15 @@ static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
qdisc_bstats_update(sch, skb);
agg_dequeue(in_serv_agg, cl, len);
- in_serv_agg->budget -= len;
+ /* If lmax is lowered, through qfq_change_class, for a class
+ * owning pending packets with larger size than the new value
+ * of lmax, then the following condition may hold.
+ */
+ if (unlikely(in_serv_agg->budget < len))
+ in_serv_agg->budget = 0;
+ else
+ in_serv_agg->budget -= len;
+
q->V += (u64)len * IWSUM;
pr_debug("qfq dequeue: len %u F %lld now %lld\n",
len, (unsigned long long) in_serv_agg->F,