pkt_sched: Use qdisc->ops->peek() instead of ->dequeue() & ->requeue()

Use qdisc->ops->peek() instead of ->dequeue() & ->requeue() pair.
After this patch the only remaining user of qdisc->ops->requeue() is
netem_enqueue(). Based on ideas of Herbert Xu, Patrick McHardy and
David S. Miller.

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 19 insertions, 29 deletions

diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index f9eac0818d18..2ee0c1a8efa9 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -480,11 +480,14 @@ static void sch_atm_dequeue(unsigned long data)
                  * If traffic is properly shaped, this won't generate nasty
                  * little bursts. Otherwise, it may ... (but that's okay)
                  */
-                while ((skb = flow->q->dequeue(flow->q))) {
-                        if (!atm_may_send(flow->vcc, skb->truesize)) {
-                                (void)flow->q->ops->requeue(skb, flow->q);
+                while ((skb = flow->q->ops->peek(flow->q))) {
+                        if (!atm_may_send(flow->vcc, skb->truesize))
                                 break;
-                        }
+
+                        skb = flow->q->dequeue(flow->q);
+                        if (unlikely(!skb))
+                                break;
+
                         pr_debug("atm_tc_dequeue: sending on class %p\n", flow);
                         /* remove any LL header somebody else has attached */
                         skb_pull(skb, skb_network_offset(skb));
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index c1e77da8cd09..ddfc40887848 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -880,28 +880,20 @@ set_passive(struct hfsc_class *cl)
          */
 }
 
-/*
- * hack to get length of first packet in queue.
- */
 static unsigned int
 qdisc_peek_len(struct Qdisc *sch)
 {
         struct sk_buff *skb;
         unsigned int len;
 
-        skb = sch->dequeue(sch);
+        skb = sch->ops->peek(sch);
         if (skb == NULL) {
                 if (net_ratelimit())
                         printk("qdisc_peek_len: non work-conserving qdisc ?\n");
                 return 0;
         }
         len = qdisc_pkt_len(skb);
-        if (unlikely(sch->ops->requeue(skb, sch) != NET_XMIT_SUCCESS)) {
-                if (net_ratelimit())
-                        printk("qdisc_peek_len: failed to requeue\n");
-                qdisc_tree_decrease_qlen(sch, 1);
-                return 0;
-        }
+
         return len;
 }
 
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 2898d9dc31eb..74fbdb52baed 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -283,25 +283,22 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
         if (sch->flags & TCQ_F_THROTTLED)
                 return NULL;
 
-        skb = q->qdisc->dequeue(q->qdisc);
+        skb = q->qdisc->ops->peek(q->qdisc);
         if (skb) {
                 const struct netem_skb_cb *cb = netem_skb_cb(skb);
                 psched_time_t now = psched_get_time();
 
                 /* if more time remaining? */
                 if (cb->time_to_send <= now) {
+                        skb = q->qdisc->dequeue(q->qdisc);
+                        if (!skb)
+                                return NULL;
+
                         pr_debug("netem_dequeue: return skb=%p\n", skb);
                         sch->q.qlen--;
                         return skb;
                 }
 
-                if (unlikely(q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS)) {
-                        qdisc_tree_decrease_qlen(q->qdisc, 1);
-                        sch->qstats.drops++;
-                        printk(KERN_ERR "netem: %s could not requeue\n",
-                               q->qdisc->ops->id);
-                }
-
                 qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
         }
 
diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 94c61598b86a..61fdc77a48d2 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -169,7 +169,7 @@ static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
         struct tbf_sched_data *q = qdisc_priv(sch);
         struct sk_buff *skb;
 
-        skb = q->qdisc->dequeue(q->qdisc);
+        skb = q->qdisc->ops->peek(q->qdisc);
 
         if (skb) {
                 psched_time_t now;
@@ -192,6 +192,10 @@ static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
                 toks -= L2T(q, len);
 
                 if ((toks|ptoks) >= 0) {
+                        skb = q->qdisc->dequeue(q->qdisc);
+                        if (unlikely(!skb))
+                                return NULL;
+
                         q->t_c = now;
                         q->tokens = toks;
                         q->ptokens = ptoks;
@@ -214,12 +218,6 @@ static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
                    (cf. CSZ, HPFQ, HFSC)
                  */
 
-                if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
-                        /* When requeue fails skb is dropped */
-                        qdisc_tree_decrease_qlen(q->qdisc, 1);
-                        sch->qstats.drops++;
-                }
-
                 sch->qstats.overlimits++;
         }
         return NULL;