[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>

3 files changed, 24 insertions, 1 deletions

diff --git a/include/linux/list.h b/include/linux/list.h
index 0f2435f92db3..9b9b0eec1e8a 100644
--- a/include/linux/list.h
+++ b/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) \
diff --git a/net/ipv4/fib_lookup.h b/net/ipv4/fib_lookup.h
index b729d97cfa93..ef6609ea0eb7 100644
--- a/net/ipv4/fib_lookup.h
+++ b/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;
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 7e4651b3caa8..d41219e8037c 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -854,6 +854,7 @@ failure:
         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 &&