sch_drr: update backlog as well

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

commit 6a73b571 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_drr.c

@@ -375,6 +375,7 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		cl->deficit = cl->quantum;
 	}
 
+	qdisc_qstats_backlog_inc(sch, skb);
 	sch->q.qlen++;
 	return err;
 }
@@ -405,6 +406,7 @@ static struct sk_buff *drr_dequeue(struct Qdisc *sch)
 
 			bstats_update(&cl->bstats, skb);
 			qdisc_bstats_update(sch, skb);
+			qdisc_qstats_backlog_dec(sch, skb);
 			sch->q.qlen--;
 			return skb;
 		}
@@ -426,6 +428,7 @@ static unsigned int drr_drop(struct Qdisc *sch)
 		if (cl->qdisc->ops->drop) {
 			len = cl->qdisc->ops->drop(cl->qdisc);
 			if (len > 0) {
+				sch->qstats.backlog -= len;
 				sch->q.qlen--;
 				if (cl->qdisc->q.qlen == 0)
 					list_del(&cl->alist);
@@ -461,6 +464,7 @@ static void drr_reset_qdisc(struct Qdisc *sch)
 			qdisc_reset(cl->qdisc);
 		}
 	}
+	sch->qstats.backlog = 0;
 	sch->q.qlen = 0;
 }