net: Optimize hard_start_xmit() return checking

Recent changes in the TX error propagation require additional checking
and masking of values returned from hard_start_xmit(), mainly to
separate cases where skb was consumed. This aim can be simplified by
changing the order of NETDEV_TX and NET_XMIT codes, because the latter
are treated similarly to negative (ERRNO) values.

After this change much simpler dev_xmit_complete() is also used in
sch_direct_xmit(), so it is moved to netdevice.h.

Additionally NET_RX definitions in netdevice.h are moved up from
between TX codes to avoid confusion while reading the TX comment.

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

net/sched/sch_generic.c

@@ -119,39 +119,26 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
 	spin_unlock(root_lock);
 
 	HARD_TX_LOCK(dev, txq, smp_processor_id());
-	if (!netif_tx_queue_stopped(txq) &&
-	    !netif_tx_queue_frozen(txq)) {
+	if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq))
 		ret = dev_hard_start_xmit(skb, dev, txq);
 
-		/* an error implies that the skb was consumed */
-		if (ret < 0)
-			ret = NETDEV_TX_OK;
-		/* all NET_XMIT codes map to NETDEV_TX_OK */
-		ret &= ~NET_XMIT_MASK;
-	}
 	HARD_TX_UNLOCK(dev, txq);
 
 	spin_lock(root_lock);
 
-	switch (ret) {
-	case NETDEV_TX_OK:
-		/* Driver sent out skb successfully */
+	if (dev_xmit_complete(ret)) {
+		/* Driver sent out skb successfully or skb was consumed */
 		ret = qdisc_qlen(q);
-		break;
-
-	case NETDEV_TX_LOCKED:
+	} else if (ret == NETDEV_TX_LOCKED) {
 		/* Driver try lock failed */
 		ret = handle_dev_cpu_collision(skb, txq, q);
-		break;
-
-	default:
+	} else {
 		/* Driver returned NETDEV_TX_BUSY - requeue skb */
 		if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
 			printk(KERN_WARNING "BUG %s code %d qlen %d\n",
 			       dev->name, ret, q->q.qlen);
 
 		ret = dev_requeue_skb(skb, q);
-		break;
 	}
 
 	if (ret && (netif_tx_queue_stopped(txq) ||