sch_qfq: keep backlog updated with qlen

BugLink: https://bugs.launchpad.net/bugs/1878232

commit 2ed5c3f0 upstream.
Reported-by: Stas Nichiporovich <stasn77@gmail.com>
Fixes: 2ccccf5f ("net_sched: update hierarchical backlog too")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/sched/sch_qfq.c

@@ -1150,6 +1150,7 @@ static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
 	if (!skb)
 		return NULL;
 
+	qdisc_qstats_backlog_dec(sch, skb);
 	sch->q.qlen--;
 	qdisc_bstats_update(sch, skb);
 
@@ -1250,6 +1251,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	}
 
 	bstats_update(&cl->bstats, skb);
+	qdisc_qstats_backlog_inc(sch, skb);
 	++sch->q.qlen;
 
 	agg = cl->agg;
@@ -1516,6 +1518,7 @@ static void qfq_reset_qdisc(struct Qdisc *sch)
 			qdisc_reset(cl->qdisc);
 		}
 	}
+	sch->qstats.backlog = 0;
 	sch->q.qlen = 0;
 }