net_sched: keep backlog updated with qlen

For gso_skb we only update qlen, backlog should be updated too.

Note, it is correct to just update these stats at one layer,
because the gso_skb is cached there.

Reported-by: Stas Nichiporovich <stasn77@gmail.com>
Fixes: 2ccccf5fb43f ("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>
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index a1fd76c..6803af1 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -691,9 +691,11 @@
 	/* we can reuse ->gso_skb because peek isn't called for root qdiscs */
 	if (!sch->gso_skb) {
 		sch->gso_skb = sch->dequeue(sch);
-		if (sch->gso_skb)
+		if (sch->gso_skb) {
 			/* it's still part of the queue */
+			qdisc_qstats_backlog_inc(sch, sch->gso_skb);
 			sch->q.qlen++;
+		}
 	}
 
 	return sch->gso_skb;
@@ -706,6 +708,7 @@
 
 	if (skb) {
 		sch->gso_skb = NULL;
+		qdisc_qstats_backlog_dec(sch, skb);
 		sch->q.qlen--;
 	} else {
 		skb = sch->dequeue(sch);
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 269dd71..f9e0e9c 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -49,6 +49,7 @@
 {
 	q->gso_skb = skb;
 	q->qstats.requeues++;
+	qdisc_qstats_backlog_inc(q, skb);
 	q->q.qlen++;	/* it's still part of the queue */
 	__netif_schedule(q);
 
@@ -92,6 +93,7 @@
 		txq = skb_get_tx_queue(txq->dev, skb);
 		if (!netif_xmit_frozen_or_stopped(txq)) {
 			q->gso_skb = NULL;
+			qdisc_qstats_backlog_dec(q, skb);
 			q->q.qlen--;
 		} else
 			skb = NULL;