netdev: add netdev_continue_rcu

This adds an RCU macro for continuing search, useful for some
network devices like vlan.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1079,6 +1079,8 @@ extern rwlock_t				dev_base_lock;		/* Device list lock */
 		list_for_each_entry_safe(d, n, &(net)->dev_base_head, dev_list)
 #define for_each_netdev_continue(net, d)		\
 		list_for_each_entry_continue(d, &(net)->dev_base_head, dev_list)
+#define for_each_netdev_continue_rcu(net, d)		\
+	list_for_each_entry_continue_rcu(d, &(net)->dev_base_head, dev_list)
 #define net_device_entry(lh)	list_entry(lh, struct net_device, dev_list)
 
 static inline struct net_device *next_net_device(struct net_device *dev)

include/linux/rculist.h

@@ -261,6 +261,20 @@ static inline void list_splice_init_rcu(struct list_head *list,
 		prefetch((pos)->next), (pos) != (head); \
 		(pos) = rcu_dereference((pos)->next))
 
+/**
+ * list_for_each_entry_continue_rcu - continue iteration over list of given type
+ * @pos:	the type * to use as a loop cursor.
+ * @head:	the head for your list.
+ * @member:	the name of the list_struct within the struct.
+ *
+ * Continue to iterate over list of given type, continuing after
+ * the current position.
+ */
+#define list_for_each_entry_continue_rcu(pos, head, member) 		\
+	for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
+	     prefetch(pos->member.next), &pos->member != (head);	\
+	     pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
+
 /**
  * hlist_del_rcu - deletes entry from hash list without re-initialization
  * @n: the element to delete from the hash list.