ipv6: fib: Add helpers to hold / drop a reference on rt6_info

Similar to commit 1c677b3d ("ipv4: fib: Add fib_info_hold() helper")
and commit b423cb10 ("ipv4: fib: Export free_fib_info()") add an
helper to hold a reference on rt6_info and export rt6_release() to drop
it and potentially release the route.

This is needed so that drivers capable of FIB offload could hold a
reference on the route before queueing it for offload and drop it after
the route has been programmed to the device's tables.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_fib.h

@@ -187,6 +187,22 @@ static inline void ip6_rt_put(struct rt6_info *rt)
 	dst_release(&rt->dst);
 }
 
+void rt6_free_pcpu(struct rt6_info *non_pcpu_rt);
+
+static inline void rt6_hold(struct rt6_info *rt)
+{
+	atomic_inc(&rt->rt6i_ref);
+}
+
+static inline void rt6_release(struct rt6_info *rt)
+{
+	if (atomic_dec_and_test(&rt->rt6i_ref)) {
+		rt6_free_pcpu(rt);
+		dst_dev_put(&rt->dst);
+		dst_release(&rt->dst);
+	}
+}
+
 enum fib6_walk_state {
 #ifdef CONFIG_IPV6_SUBTREES
 	FWS_S,

net/ipv6/ip6_fib.c

@@ -154,7 +154,7 @@ static void node_free(struct fib6_node *fn)
 	kmem_cache_free(fib6_node_kmem, fn);
 }
 
-static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
+void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
 {
 	int cpu;
 
@@ -177,15 +177,7 @@ static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
 	free_percpu(non_pcpu_rt->rt6i_pcpu);
 	non_pcpu_rt->rt6i_pcpu = NULL;
 }
-
-static void rt6_release(struct rt6_info *rt)
-{
-	if (atomic_dec_and_test(&rt->rt6i_ref)) {
-		rt6_free_pcpu(rt);
-		dst_dev_put(&rt->dst);
-		dst_release(&rt->dst);
-	}
-}
+EXPORT_SYMBOL_GPL(rt6_free_pcpu);
 
 static void fib6_link_table(struct net *net, struct fib6_table *tb)
 {