pkt_sched: Add qdisc->ops->peek() implementation.

Add qdisc->ops->peek() implementation for work-conserving qdiscs.
With feedback from Patrick McHardy.

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

8 files changed, 69 insertions, 0 deletions

diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index 43d37256c15e..f9eac0818d18 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -522,6 +522,15 @@ static struct sk_buff *atm_tc_dequeue(struct Qdisc *sch)
         return skb;
 }
 
+static struct sk_buff *atm_tc_peek(struct Qdisc *sch)
+{
+        struct atm_qdisc_data *p = qdisc_priv(sch);
+
+        pr_debug("atm_tc_peek(sch %p,[qdisc %p])\n", sch, p);
+
+        return p->link.q->ops->peek(p->link.q);
+}
+
 static int atm_tc_requeue(struct sk_buff *skb, struct Qdisc *sch)
 {
         struct atm_qdisc_data *p = qdisc_priv(sch);
@@ -694,6 +703,7 @@ static struct Qdisc_ops atm_qdisc_ops __read_mostly = {
         .priv_size      = sizeof(struct atm_qdisc_data),
         .enqueue        = atm_tc_enqueue,
         .dequeue        = atm_tc_dequeue,
+        .peek           = atm_tc_peek,
         .requeue        = atm_tc_requeue,
         .drop           = atm_tc_drop,
         .init           = atm_tc_init,
diff --git a/net/sched/sch_blackhole.c b/net/sched/sch_blackhole.c
index 507fb488bc98..094a874b48bc 100644
--- a/net/sched/sch_blackhole.c
+++ b/net/sched/sch_blackhole.c
@@ -33,6 +33,7 @@ static struct Qdisc_ops blackhole_qdisc_ops __read_mostly = {
         .priv_size      = 0,
         .enqueue        = blackhole_enqueue,
         .dequeue        = blackhole_dequeue,
+        .peek           = blackhole_dequeue,
         .owner          = THIS_MODULE,
 };
 
diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
index ba43aab3a851..3e491479ea86 100644
--- a/net/sched/sch_dsmark.c
+++ b/net/sched/sch_dsmark.c
@@ -313,6 +313,15 @@ 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("dsmark_peek(sch %p,[qdisc %p])\n", sch, p);
+
+        return p->q->ops->peek(p->q);
+}
+
 static int dsmark_requeue(struct sk_buff *skb, struct Qdisc *sch)
 {
         struct dsmark_qdisc_data *p = qdisc_priv(sch);
@@ -496,6 +505,7 @@ 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,
         .requeue        =       dsmark_requeue,
         .drop           =       dsmark_drop,
         .init           =       dsmark_init,
diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index c1ad6b8de105..cb20ee3b9fc2 100644
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -602,6 +602,7 @@ static struct Qdisc_ops gred_qdisc_ops __read_mostly = {
         .priv_size      =       sizeof(struct gred_sched),
         .enqueue        =       gred_enqueue,
         .dequeue        =       gred_dequeue,
+        .peek           =       qdisc_peek_head,
         .requeue        =       gred_requeue,
         .drop           =       gred_drop,
         .init           =       gred_init,
diff --git a/net/sched/sch_multiq.c b/net/sched/sch_multiq.c
index 915f3149dde2..155648d23b7c 100644
--- a/net/sched/sch_multiq.c
+++ b/net/sched/sch_multiq.c
@@ -155,6 +155,34 @@ static struct sk_buff *multiq_dequeue(struct Qdisc *sch)
 
 }
 
+static struct sk_buff *multiq_peek(struct Qdisc *sch)
+{
+        struct multiq_sched_data *q = qdisc_priv(sch);
+        unsigned int curband = q->curband;
+        struct Qdisc *qdisc;
+        struct sk_buff *skb;
+        int band;
+
+        for (band = 0; band < q->bands; band++) {
+                /* cycle through bands to ensure fairness */
+                curband++;
+                if (curband >= q->bands)
+                        curband = 0;
+
+                /* Check that target subqueue is available before
+                 * pulling an skb to avoid excessive requeues
+                 */
+                if (!__netif_subqueue_stopped(qdisc_dev(sch), curband)) {
+                        qdisc = q->queues[curband];
+                        skb = qdisc->ops->peek(qdisc);
+                        if (skb)
+                                return skb;
+                }
+        }
+        return NULL;
+
+}
+
 static unsigned int multiq_drop(struct Qdisc *sch)
 {
         struct multiq_sched_data *q = qdisc_priv(sch);
@@ -451,6 +479,7 @@ static struct Qdisc_ops multiq_qdisc_ops __read_mostly = {
         .priv_size      =       sizeof(struct multiq_sched_data),
         .enqueue        =       multiq_enqueue,
         .dequeue        =       multiq_dequeue,
+        .peek           =       multiq_peek,
         .requeue        =       multiq_requeue,
         .drop           =       multiq_drop,
         .init           =       multiq_init,
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index a11959908d9a..2898d9dc31eb 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -541,6 +541,7 @@ static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
         .priv_size      =       sizeof(struct fifo_sched_data),
         .enqueue        =       tfifo_enqueue,
         .dequeue        =       qdisc_dequeue_head,
+        .peek           =       qdisc_peek_head,
         .requeue        =       qdisc_requeue,
         .drop           =       qdisc_queue_drop,
         .init           =       tfifo_init,
diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c
index 5da05839e225..7abc51454c2d 100644
--- a/net/sched/sch_red.c
+++ b/net/sched/sch_red.c
@@ -140,6 +140,14 @@ static struct sk_buff * red_dequeue(struct Qdisc* sch)
         return skb;
 }
 
+static struct sk_buff * red_peek(struct Qdisc* sch)
+{
+        struct red_sched_data *q = qdisc_priv(sch);
+        struct Qdisc *child = q->qdisc;
+
+        return child->ops->peek(child);
+}
+
 static unsigned int red_drop(struct Qdisc* sch)
 {
         struct red_sched_data *q = qdisc_priv(sch);
@@ -361,6 +369,7 @@ static struct Qdisc_ops red_qdisc_ops __read_mostly = {
         .cl_ops         =       &red_class_ops,
         .enqueue        =       red_enqueue,
         .dequeue        =       red_dequeue,
+        .peek           =       red_peek,
         .requeue        =       red_requeue,
         .drop           =       red_drop,
         .init           =       red_init,
diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c
index d35ef059abb1..bf03e7fa1849 100644
--- a/net/sched/sch_teql.c
+++ b/net/sched/sch_teql.c
@@ -123,6 +123,13 @@ teql_dequeue(struct Qdisc* sch)
         return skb;
 }
 
+static struct sk_buff *
+teql_peek(struct Qdisc* sch)
+{
+        /* teql is meant to be used as root qdisc */
+        return NULL;
+}
+
 static __inline__ void
 teql_neigh_release(struct neighbour *n)
 {
@@ -433,6 +440,7 @@ static __init void teql_master_setup(struct net_device *dev)
 
         ops->enqueue    =       teql_enqueue;
         ops->dequeue    =       teql_dequeue;
+        ops->peek       =       teql_peek;
         ops->requeue    =       teql_requeue;
         ops->init       =       teql_qdisc_init;
         ops->reset      =       teql_reset;