net_sched/sfq: update hierarchical backlog when drop packet

When sfq_enqueue() drops head packet or packet from another queue it
have to update backlog at upper qdiscs too.

Fixes: 2ccccf5f ("net_sched: update hierarchical backlog too")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_sfq.c

@@ -437,6 +437,7 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 		qdisc_drop(head, sch, to_free);
 
 		slot_queue_add(slot, skb);
+		qdisc_tree_reduce_backlog(sch, 0, delta);
 		return NET_XMIT_CN;
 	}
 
@@ -468,8 +469,10 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 	/* Return Congestion Notification only if we dropped a packet
 	 * from this flow.
 	 */
-	if (qlen != slot->qlen)
+	if (qlen != slot->qlen) {
+		qdisc_tree_reduce_backlog(sch, 0, dropped - qdisc_pkt_len(skb));
 		return NET_XMIT_CN;
+	}
 
 	/* As we dropped a packet, better let upper stack know this */
 	qdisc_tree_reduce_backlog(sch, 1, dropped);