4 files changed, 108 insertions, 51 deletions

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 82a3191375f5..f911ec7598ef 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -87,6 +87,9 @@ extern struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
 extern void qdisc_put_rtab(struct qdisc_rate_table *tab);
 extern void qdisc_put_stab(struct qdisc_size_table *tab);
 extern void qdisc_warn_nonwc(char *txt, struct Qdisc *qdisc);
+extern int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
+                           struct net_device *dev, struct netdev_queue *txq,
+                           spinlock_t *root_lock);
 
 extern void __qdisc_run(struct Qdisc *q);
 
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 964ffa0d8815..84b3fc2aef0f 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -45,6 +45,7 @@ struct Qdisc
 #define TCQ_F_BUILTIN           1
 #define TCQ_F_THROTTLED         2
 #define TCQ_F_INGRESS           4
+#define TCQ_F_CAN_BYPASS        8
 #define TCQ_F_WARN_NONWC        (1 << 16)
         int                     padded;
         struct Qdisc_ops        *ops;
@@ -182,6 +183,11 @@ struct qdisc_skb_cb {
         char                    data[];
 };
 
+static inline int qdisc_qlen(struct Qdisc *q)
+{
+        return q->q.qlen;
+}
+
 static inline struct qdisc_skb_cb *qdisc_skb_cb(struct sk_buff *skb)
 {
         return (struct qdisc_skb_cb *)skb->cb;
@@ -387,13 +393,18 @@ static inline int qdisc_enqueue_root(struct sk_buff *skb, struct Qdisc *sch)
         return qdisc_enqueue(skb, sch) & NET_XMIT_MASK;
 }
 
+static inline void __qdisc_update_bstats(struct Qdisc *sch, unsigned int len)
+{
+        sch->bstats.bytes += len;
+        sch->bstats.packets++;
+}
+
 static inline int __qdisc_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch,
                                        struct sk_buff_head *list)
 {
         __skb_queue_tail(list, skb);
         sch->qstats.backlog += qdisc_pkt_len(skb);
-        sch->bstats.bytes += qdisc_pkt_len(skb);
-        sch->bstats.packets++;
+        __qdisc_update_bstats(sch, qdisc_pkt_len(skb));
 
         return NET_XMIT_SUCCESS;
 }
diff --git a/net/core/dev.c b/net/core/dev.c
index f01a9c41f112..a0bc087616a4 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1786,6 +1786,40 @@ static struct netdev_queue *dev_pick_tx(struct net_device *dev,
         return netdev_get_tx_queue(dev, queue_index);
 }
 
+static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
+                                 struct net_device *dev,
+                                 struct netdev_queue *txq)
+{
+        spinlock_t *root_lock = qdisc_lock(q);
+        int rc;
+
+        spin_lock(root_lock);
+        if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) {
+                kfree_skb(skb);
+                rc = NET_XMIT_DROP;
+        } else if ((q->flags & TCQ_F_CAN_BYPASS) && !qdisc_qlen(q) &&
+                   !test_and_set_bit(__QDISC_STATE_RUNNING, &q->state)) {
+                /*
+                 * This is a work-conserving queue; there are no old skbs
+                 * waiting to be sent out; and the qdisc is not running -
+                 * xmit the skb directly.
+                 */
+                __qdisc_update_bstats(q, skb->len);
+                if (sch_direct_xmit(skb, q, dev, txq, root_lock))
+                        __qdisc_run(q);
+                else
+                        clear_bit(__QDISC_STATE_RUNNING, &q->state);
+
+                rc = NET_XMIT_SUCCESS;
+        } else {
+                rc = qdisc_enqueue_root(skb, q);
+                qdisc_run(q);
+        }
+        spin_unlock(root_lock);
+
+        return rc;
+}
+
 /**
  *      dev_queue_xmit - transmit a buffer
  *      @skb: buffer to transmit
@@ -1859,19 +1893,7 @@ gso:
         skb->tc_verd = SET_TC_AT(skb->tc_verd,AT_EGRESS);
 #endif
         if (q->enqueue) {
-                spinlock_t *root_lock = qdisc_lock(q);
-
-                spin_lock(root_lock);
-
-                if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) {
-                        kfree_skb(skb);
-                        rc = NET_XMIT_DROP;
-                } else {
-                        rc = qdisc_enqueue_root(skb, q);
-                        qdisc_run(q);
-                }
-                spin_unlock(root_lock);
-
+                rc = __dev_xmit_skb(skb, q, dev, txq);
                 goto out;
         }
 
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 27d03816ec3e..693df7ae33d8 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -37,15 +37,11 @@
  * - updates to tree and tree walking are only done under the rtnl mutex.
  */
 
-static inline int qdisc_qlen(struct Qdisc *q)
-{
-        return q->q.qlen;
-}
-
 static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
 {
         q->gso_skb = skb;
         q->qstats.requeues++;
+        q->q.qlen++;    /* it's still part of the queue */
         __netif_schedule(q);
 
         return 0;
@@ -61,9 +57,11 @@ static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
 
                 /* check the reason of requeuing without tx lock first */
                 txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
-                if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq))
+                if (!netif_tx_queue_stopped(txq) &&
+                    !netif_tx_queue_frozen(txq)) {
                         q->gso_skb = NULL;
-                else
+                        q->q.qlen--;
+                } else
                         skb = NULL;
         } else {
                 skb = q->dequeue(q);
@@ -103,44 +101,23 @@ static inline int handle_dev_cpu_collision(struct sk_buff *skb,
 }
 
 /*
- * NOTE: Called under qdisc_lock(q) with locally disabled BH.
- *
- * __QDISC_STATE_RUNNING guarantees only one CPU can process
- * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
- * this queue.
- *
- *  netif_tx_lock serializes accesses to device driver.
- *
- *  qdisc_lock(q) and netif_tx_lock are mutually exclusive,
- *  if one is grabbed, another must be free.
- *
- * Note, that this procedure can be called by a watchdog timer
+ * Transmit one skb, and handle the return status as required. Holding the
+ * __QDISC_STATE_RUNNING bit guarantees that only one CPU can execute this
+ * function.
  *
  * Returns to the caller:
  *                              0  - queue is empty or throttled.
  *                              >0 - queue is not empty.
- *
  */
-static inline int qdisc_restart(struct Qdisc *q)
+int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
+                    struct net_device *dev, struct netdev_queue *txq,
+                    spinlock_t *root_lock)
 {
-        struct netdev_queue *txq;
         int ret = NETDEV_TX_BUSY;
-        struct net_device *dev;
-        spinlock_t *root_lock;
-        struct sk_buff *skb;
-
-        /* Dequeue packet */
-        if (unlikely((skb = dequeue_skb(q)) == NULL))
-                return 0;
-
-        root_lock = qdisc_lock(q);
 
         /* And release qdisc */
         spin_unlock(root_lock);
 
-        dev = qdisc_dev(q);
-        txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
-
         HARD_TX_LOCK(dev, txq, smp_processor_id());
         if (!netif_tx_queue_stopped(txq) &&
             !netif_tx_queue_frozen(txq))
@@ -177,6 +154,44 @@ static inline int qdisc_restart(struct Qdisc *q)
         return ret;
 }
 
+/*
+ * NOTE: Called under qdisc_lock(q) with locally disabled BH.
+ *
+ * __QDISC_STATE_RUNNING guarantees only one CPU can process
+ * this qdisc at a time. qdisc_lock(q) serializes queue accesses for
+ * this queue.
+ *
+ *  netif_tx_lock serializes accesses to device driver.
+ *
+ *  qdisc_lock(q) and netif_tx_lock are mutually exclusive,
+ *  if one is grabbed, another must be free.
+ *
+ * Note, that this procedure can be called by a watchdog timer
+ *
+ * Returns to the caller:
+ *                              0  - queue is empty or throttled.
+ *                              >0 - queue is not empty.
+ *
+ */
+static inline int qdisc_restart(struct Qdisc *q)
+{
+        struct netdev_queue *txq;
+        struct net_device *dev;
+        spinlock_t *root_lock;
+        struct sk_buff *skb;
+
+        /* Dequeue packet */
+        skb = dequeue_skb(q);
+        if (unlikely(!skb))
+                return 0;
+
+        root_lock = qdisc_lock(q);
+        dev = qdisc_dev(q);
+        txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
+
+        return sch_direct_xmit(skb, q, dev, txq, root_lock);
+}
+
 void __qdisc_run(struct Qdisc *q)
 {
         unsigned long start_time = jiffies;
@@ -547,8 +562,11 @@ void qdisc_reset(struct Qdisc *qdisc)
         if (ops->reset)
                 ops->reset(qdisc);
 
-        kfree_skb(qdisc->gso_skb);
-        qdisc->gso_skb = NULL;
+        if (qdisc->gso_skb) {
+                kfree_skb(qdisc->gso_skb);
+                qdisc->gso_skb = NULL;
+                qdisc->q.qlen = 0;
+        }
 }
 EXPORT_SYMBOL(qdisc_reset);
 
@@ -605,6 +623,9 @@ static void attach_one_default_qdisc(struct net_device *dev,
                         printk(KERN_INFO "%s: activation failed\n", dev->name);
                         return;
                 }
+
+                /* Can by-pass the queue discipline for default qdisc */
+                qdisc->flags |= TCQ_F_CAN_BYPASS;
         } else {
                 qdisc =  &noqueue_qdisc;
         }