sch_tbf: update backlog as well

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

commit 8d5958f4 upstream.

Fixes: 2ccccf5f ("net_sched: update hierarchical backlog too")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.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_tbf.c

@@ -197,6 +197,7 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		return ret;
 	}
 
+	qdisc_qstats_backlog_inc(sch, skb);
 	sch->q.qlen++;
 	return NET_XMIT_SUCCESS;
 }
@@ -207,6 +208,7 @@ static unsigned int tbf_drop(struct Qdisc *sch)
 	unsigned int len = 0;
 
 	if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
+		sch->qstats.backlog -= len;
 		sch->q.qlen--;
 		qdisc_qstats_drop(sch);
 	}
@@ -253,6 +255,7 @@ static struct sk_buff *tbf_dequeue(struct Qdisc *sch)
 			q->t_c = now;
 			q->tokens = toks;
 			q->ptokens = ptoks;
+			qdisc_qstats_backlog_dec(sch, skb);
 			sch->q.qlen--;
 			qdisc_unthrottled(sch);
 			qdisc_bstats_update(sch, skb);
@@ -284,6 +287,7 @@ static void tbf_reset(struct Qdisc *sch)
 	struct tbf_sched_data *q = qdisc_priv(sch);
 
 	qdisc_reset(q->qdisc);
+	sch->qstats.backlog = 0;
 	sch->q.qlen = 0;
 	q->t_c = ktime_get_ns();
 	q->tokens = q->buffer;