pkt_sched: Add peek emulation for non-work-conserving qdiscs.
Jarek Poplawski [Fri, 31 Oct 2008 07:47:01 +0000 (00:47 -0700)]
This patch adds qdisc_peek_dequeued() wrapper to emulate peek method
with qdisc->dequeue() and storing "peeked" skb in qdisc->gso_skb until
dequeuing. This is mainly for compatibility reasons not to break some
strange configs because peeking is expected for non-work-conserving
parent qdiscs to query work-conserving child qdiscs.

This implementation requires using qdisc_dequeue_peeked() wrapper
instead of directly calling qdisc->dequeue() for all qdiscs ever
querried with qdisc->ops->peek() or qdisc_peek_dequeued().

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

include/net/sch_generic.h
net/sched/sch_atm.c
net/sched/sch_cbq.c
net/sched/sch_hfsc.c
net/sched/sch_htb.c
net/sched/sch_netem.c
net/sched/sch_tbf.c

index da6839a..9dcb5bf 100644 (file)
@@ -438,6 +438,29 @@ static inline struct sk_buff *qdisc_peek_head(struct Qdisc *sch)
        return skb_peek(&sch->q);
 }
 
+/* generic pseudo peek method for non-work-conserving qdisc */
+static inline struct sk_buff *qdisc_peek_dequeued(struct Qdisc *sch)
+{
+       /* we can reuse ->gso_skb because peek isn't called for root qdiscs */
+       if (!sch->gso_skb)
+               sch->gso_skb = sch->dequeue(sch);
+
+       return sch->gso_skb;
+}
+
+/* use instead of qdisc->dequeue() for all qdiscs queried with ->peek() */
+static inline struct sk_buff *qdisc_dequeue_peeked(struct Qdisc *sch)
+{
+       struct sk_buff *skb = sch->gso_skb;
+
+       if (skb)
+               sch->gso_skb = NULL;
+       else
+               skb = sch->dequeue(sch);
+
+       return skb;
+}
+
 static inline int __qdisc_requeue(struct sk_buff *skb, struct Qdisc *sch,
                                  struct sk_buff_head *list)
 {
index 2ee0c1a..6eb9a65 100644 (file)
@@ -484,7 +484,7 @@ static void sch_atm_dequeue(unsigned long data)
                        if (!atm_may_send(flow->vcc, skb->truesize))
                                break;
 
-                       skb = flow->q->dequeue(flow->q);
+                       skb = qdisc_dequeue_peeked(flow->q);
                        if (unlikely(!skb))
                                break;
 
@@ -519,7 +519,7 @@ static struct sk_buff *atm_tc_dequeue(struct Qdisc *sch)
 
        pr_debug("atm_tc_dequeue(sch %p,[qdisc %p])\n", sch, p);
        tasklet_schedule(&p->task);
-       skb = p->link.q->dequeue(p->link.q);
+       skb = qdisc_dequeue_peeked(p->link.q);
        if (skb)
                sch->q.qlen--;
        return skb;
index 03e389e..63efa70 100644 (file)
@@ -2066,6 +2066,7 @@ static struct Qdisc_ops cbq_qdisc_ops __read_mostly = {
        .priv_size      =       sizeof(struct cbq_sched_data),
        .enqueue        =       cbq_enqueue,
        .dequeue        =       cbq_dequeue,
+       .peek           =       qdisc_peek_dequeued,
        .requeue        =       cbq_requeue,
        .drop           =       cbq_drop,
        .init           =       cbq_init,
index ddfc408..d90b165 100644 (file)
@@ -1634,7 +1634,7 @@ hfsc_dequeue(struct Qdisc *sch)
                }
        }
 
-       skb = cl->qdisc->dequeue(cl->qdisc);
+       skb = qdisc_dequeue_peeked(cl->qdisc);
        if (skb == NULL) {
                if (net_ratelimit())
                        printk("HFSC: Non-work-conserving qdisc ?\n");
@@ -1727,6 +1727,7 @@ static struct Qdisc_ops hfsc_qdisc_ops __read_mostly = {
        .dump           = hfsc_dump_qdisc,
        .enqueue        = hfsc_enqueue,
        .dequeue        = hfsc_dequeue,
+       .peek           = qdisc_peek_dequeued,
        .requeue        = hfsc_requeue,
        .drop           = hfsc_drop,
        .cl_ops         = &hfsc_class_ops,
index d14f020..3fda819 100644 (file)
@@ -1565,6 +1565,7 @@ static struct Qdisc_ops htb_qdisc_ops __read_mostly = {
        .priv_size      =       sizeof(struct htb_sched),
        .enqueue        =       htb_enqueue,
        .dequeue        =       htb_dequeue,
+       .peek           =       qdisc_peek_dequeued,
        .requeue        =       htb_requeue,
        .drop           =       htb_drop,
        .init           =       htb_init,
index 74fbdb5..3080bd6 100644 (file)
@@ -290,8 +290,8 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 
                /* if more time remaining? */
                if (cb->time_to_send <= now) {
-                       skb = q->qdisc->dequeue(q->qdisc);
-                       if (!skb)
+                       skb = qdisc_dequeue_peeked(q->qdisc);
+                       if (unlikely(!skb))
                                return NULL;
 
                        pr_debug("netem_dequeue: return skb=%p\n", skb);
@@ -714,6 +714,7 @@ static struct Qdisc_ops netem_qdisc_ops __read_mostly = {
        .priv_size      =       sizeof(struct netem_sched_data),
        .enqueue        =       netem_enqueue,
        .dequeue        =       netem_dequeue,
+       .peek           =       qdisc_peek_dequeued,
        .requeue        =       netem_requeue,
        .drop           =       netem_drop,
        .init           =       netem_init,
index 61fdc77..435076c 100644 (file)
@@ -192,7 +192,7 @@ static struct sk_buff *tbf_dequeue(struct Qdisc* sch)
                toks -= L2T(q, len);
 
                if ((toks|ptoks) >= 0) {
-                       skb = q->qdisc->dequeue(q->qdisc);
+                       skb = qdisc_dequeue_peeked(q->qdisc);
                        if (unlikely(!skb))
                                return NULL;
 
@@ -467,6 +467,7 @@ static struct Qdisc_ops tbf_qdisc_ops __read_mostly = {
        .priv_size      =       sizeof(struct tbf_sched_data),
        .enqueue        =       tbf_enqueue,
        .dequeue        =       tbf_dequeue,
+       .peek           =       qdisc_peek_dequeued,
        .requeue        =       tbf_requeue,
        .drop           =       tbf_drop,
        .init           =       tbf_init,