[IPV4]: Prepare FIB core for RCU.

* RCU versions of hlist_***_rcu
* fib_alias partial rcu port just whats needed now.
Signed-off-by: Robert Olsson <Robert.Olsson@data.slu.se>
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/list.h

@@ -634,6 +634,27 @@ static inline void hlist_add_after(struct hlist_node *n,
 		next->next->pprev  = &next->next;
 }
 
+static inline void hlist_add_before_rcu(struct hlist_node *n,
+					struct hlist_node *next)
+{
+	n->pprev = next->pprev;
+	n->next = next;
+	smp_wmb();
+	next->pprev = &n->next;
+	*(n->pprev) = n;
+}
+
+static inline void hlist_add_after_rcu(struct hlist_node *prev,
+				       struct hlist_node *n)
+{
+	n->next = prev->next;
+	n->pprev = &prev->next;
+	smp_wmb();
+	prev->next = n;
+	if (n->next)
+		n->next->pprev = &n->next;
+}
+
 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
 
 #define hlist_for_each(pos, head) \

net/ipv4/fib_lookup.h

@@ -7,6 +7,7 @@
 
 struct fib_alias {
 	struct list_head	fa_list;
+	struct rcu_head rcu;
 	struct fib_info		*fa_info;
 	u8			fa_tos;
 	u8			fa_type;

net/ipv4/fib_semantics.c

@@ -854,6 +854,7 @@ fib_create_info(const struct rtmsg *r, struct kern_rta *rta,
 	return NULL;
 }
 
+/* Note! fib_semantic_match intentionally uses  RCU list functions. */
 int fib_semantic_match(struct list_head *head, const struct flowi *flp,
 		       struct fib_result *res, __u32 zone, __u32 mask, 
 			int prefixlen)
@@ -861,7 +862,7 @@ int fib_semantic_match(struct list_head *head, const struct flowi *flp,
 	struct fib_alias *fa;
 	int nh_sel = 0;
 
-	list_for_each_entry(fa, head, fa_list) {
+	list_for_each_entry_rcu(fa, head, fa_list) {
 		int err;
 
 		if (fa->fa_tos &&