net,rcu: convert call_rcu(net_generic_release) to kfree_rcu()

The rcu callback net_generic_release() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(net_generic_release).

Signed-off-by: Lai Jiangshan <[e-mail]>
Acked-by: David S. Miller <[e-mail]>
Signed-off-by: Paul E. McKenney <[e-mail]>
Reviewed-by: Josh Triplett <[e-mail]>

net/core/net_namespace.c

···
 
 #define INITIAL_NET_GEN_PTRS	13 /* +1 for len +2 for rcu_head */
 
-static void net_generic_release(struct rcu_head *rcu)
-{
-	struct net_generic *ng;
-
-	ng = container_of(rcu, struct net_generic, rcu);
-	kfree(ng);
-}
-
 static int net_assign_generic(struct net *net, int id, void *data)
 {
 	struct net_generic *ng, *old_ng;
···
 	memcpy(&ng->ptr, &old_ng->ptr, old_ng->len * sizeof(void*));
 
 	rcu_assign_pointer(net->gen, ng);
-	call_rcu(&old_ng->rcu, net_generic_release);
+	kfree_rcu(old_ng, rcu);
 assign:
 	ng->ptr[id - 1] = data;
 	return 0;