[VLAN]: Avoid a 4-order allocation.

This patch splits the vlan_group struct into a multi-allocated struct. On
x86_64, the size of the original struct is a little more than 32KB, causing
a 4-order allocation, which is prune to problems caused by buddy-system
external fragmentation conditions.

I couldn't just use vmalloc() because vfree() cannot be called in the
softirq context of the RCU callback.

Signed-off-by: Dan Aloni <da-x@monatomic.org>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ixgb/ixgb_main.c b/drivers/net/ixgb/ixgb_main.c
index 0c36828..afc2ec7 100644
--- a/drivers/net/ixgb/ixgb_main.c
+++ b/drivers/net/ixgb/ixgb_main.c
@@ -2213,8 +2213,7 @@
 
 	ixgb_irq_disable(adapter);
 
-	if(adapter->vlgrp)
-		adapter->vlgrp->vlan_devices[vid] = NULL;
+	vlan_group_set_device(adapter->vlgrp, vid, NULL);
 
 	ixgb_irq_enable(adapter);
 
@@ -2234,7 +2233,7 @@
 	if(adapter->vlgrp) {
 		uint16_t vid;
 		for(vid = 0; vid < VLAN_GROUP_ARRAY_LEN; vid++) {
-			if(!adapter->vlgrp->vlan_devices[vid])
+			if(!vlan_group_get_device(adapter->vlgrp, vid))
 				continue;
 			ixgb_vlan_rx_add_vid(adapter->netdev, vid);
 		}