net_sched: dsmark: use qdisc_dequeue_peeked()

[Kyeong Yoo <Kyeong.Yoo@alliedtelesis.co.nz>]

This fix is for dsmark similar to 3557619f0f6f7496ed453d4825e24958ab1884e0,
and makes use of qdisc_dequeue_peeked() instead of direct dequeue() call.

First time, wrr peeks dsmark, which will then peek into sfq.
sfq dequeues an skb and it's stored in sch->gso_skb.
Next time, wrr tries to dequeue from dsmark, which will call sfq dequeue
directly. This results skipping the previously peeked skb.

So changed dsmark dequeue to call qdisc_dequeue_peeked() instead to use
peeked skb if exists.

Also replaced dsmark peek to use qdisc_peek_dequeued() which works correctly
if previously peeked skb still exists.

Signed-off-by: Kyeong Yoo <kyeong.yoo@alliedtelesis.co.nz>

diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
index f357f34..8fa3a4f 100644
--- a/net/sched/sch_dsmark.c
+++ b/net/sched/sch_dsmark.c
@@ -281,7 +281,7 @@ static struct sk_buff *dsmark_dequeue(struct Qdisc *sch)
 
 	pr_debug("%s(sch %p,[qdisc %p])\n", __func__, sch, p);
 
-	skb = p->q->ops->dequeue(p->q);
+	skb = qdisc_dequeue_peeked(p->q);
 	if (skb == NULL)
 		return NULL;
 
@@ -315,15 +315,6 @@ static struct sk_buff *dsmark_dequeue(struct Qdisc *sch)
 	return skb;
 }
 
-static struct sk_buff *dsmark_peek(struct Qdisc *sch)
-{
-	struct dsmark_qdisc_data *p = qdisc_priv(sch);
-
-	pr_debug("%s(sch %p,[qdisc %p])\n", __func__, sch, p);
-
-	return p->q->ops->peek(p->q);
-}
-
 static unsigned int dsmark_drop(struct Qdisc *sch)
 {
 	struct dsmark_qdisc_data *p = qdisc_priv(sch);
@@ -491,7 +482,7 @@ static struct Qdisc_ops dsmark_qdisc_ops __read_mostly = {
 	.priv_size	=	sizeof(struct dsmark_qdisc_data),
 	.enqueue	=	dsmark_enqueue,
 	.dequeue	=	dsmark_dequeue,
-	.peek		=	dsmark_peek,
+	.peek		=	qdisc_peek_dequeued,
 	.drop		=	dsmark_drop,
 	.init		=	dsmark_init,
 	.reset		=	dsmark_reset,