sch_hhf: fix return value of hhf_drop()

Similar to commit c0afd9ce4d6a ("fq_codel: fix return value of fq_codel_drop()")
->drop() is supposed to return the number of bytes it dropped,
but hhf_drop () returns the id of the bucket where it drops
a packet from.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Terry Lam <vtlam@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_hhf.c

@@ -368,6 +368,15 @@ static unsigned int hhf_drop(struct Qdisc *sch)
 	return bucket - q->buckets;
 }
 
+static unsigned int hhf_qdisc_drop(struct Qdisc *sch)
+{
+	unsigned int prev_backlog;
+
+	prev_backlog = sch->qstats.backlog;
+	hhf_drop(sch);
+	return prev_backlog - sch->qstats.backlog;
+}
+
 static int hhf_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 {
 	struct hhf_sched_data *q = qdisc_priv(sch);
@@ -696,7 +705,7 @@ static struct Qdisc_ops hhf_qdisc_ops __read_mostly = {
 	.enqueue	=	hhf_enqueue,
 	.dequeue	=	hhf_dequeue,
 	.peek		=	qdisc_peek_dequeued,
-	.drop		=	hhf_drop,
+	.drop		=	hhf_qdisc_drop,
 	.init		=	hhf_init,
 	.reset		=	hhf_reset,
 	.destroy	=	hhf_destroy,