[NET] NETNS: Omit net_device->nd_net without CONFIG_NET_NS.

Introduce per-net_device inlines: dev_net(), dev_net_set().
Without CONFIG_NET_NS, no namespace other than &init_net exists.
Let's explicitly define them to help compiler optimizations.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/core/dev.c b/net/core/dev.c
index aebd086..8125348 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -216,7 +216,7 @@
 /* Device list insertion */
 static int list_netdevice(struct net_device *dev)
 {
-	struct net *net = dev->nd_net;
+	struct net *net = dev_net(dev);
 
 	ASSERT_RTNL();
 
@@ -852,8 +852,8 @@
 	struct net *net;
 	int ret;
 
-	BUG_ON(!dev->nd_net);
-	net = dev->nd_net;
+	BUG_ON(!dev_net(dev));
+	net = dev_net(dev);
 	ret = __dev_alloc_name(net, name, buf);
 	if (ret >= 0)
 		strlcpy(dev->name, buf, IFNAMSIZ);
@@ -877,9 +877,9 @@
 	struct net *net;
 
 	ASSERT_RTNL();
-	BUG_ON(!dev->nd_net);
+	BUG_ON(!dev_net(dev));
 
-	net = dev->nd_net;
+	net = dev_net(dev);
 	if (dev->flags & IFF_UP)
 		return -EBUSY;
 
@@ -2615,7 +2615,7 @@
 
 	if (v == SEQ_START_TOKEN)
 		seq_puts(seq, "Type Device      Function\n");
-	else if (pt->dev == NULL || pt->dev->nd_net == seq_file_net(seq)) {
+	else if (pt->dev == NULL || dev_net(pt->dev) == seq_file_net(seq)) {
 		if (pt->type == htons(ETH_P_ALL))
 			seq_puts(seq, "ALL ");
 		else
@@ -3689,8 +3689,8 @@
 
 	/* When net_device's are persistent, this will be fatal. */
 	BUG_ON(dev->reg_state != NETREG_UNINITIALIZED);
-	BUG_ON(!dev->nd_net);
-	net = dev->nd_net;
+	BUG_ON(!dev_net(dev));
+	net = dev_net(dev);
 
 	spin_lock_init(&dev->queue_lock);
 	spin_lock_init(&dev->_xmit_lock);
@@ -4011,7 +4011,7 @@
 	dev = (struct net_device *)
 		(((long)p + NETDEV_ALIGN_CONST) & ~NETDEV_ALIGN_CONST);
 	dev->padded = (char *)dev - (char *)p;
-	dev->nd_net = &init_net;
+	dev_net_set(dev, &init_net);
 
 	if (sizeof_priv) {
 		dev->priv = ((char *)dev +
@@ -4136,7 +4136,7 @@
 
 	/* Get out if there is nothing todo */
 	err = 0;
-	if (dev->nd_net == net)
+	if (dev_net(dev) == net)
 		goto out;
 
 	/* Pick the destination device name, and ensure
@@ -4187,7 +4187,7 @@
 	dev_addr_discard(dev);
 
 	/* Actually switch the network namespace */
-	dev->nd_net = net;
+	dev_net_set(dev, net);
 
 	/* Assign the new device name */
 	if (destname != dev->name)