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

The rcu callback __nf_ct_ext_free_rcu() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(__nf_ct_ext_free_rcu).
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

net/netfilter/nf_conntrack_extend.c

@@ -68,12 +68,6 @@ nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
 	return (void *)(*ext) + off;
 }
 
-static void __nf_ct_ext_free_rcu(struct rcu_head *head)
-{
-	struct nf_ct_ext *ext = container_of(head, struct nf_ct_ext, rcu);
-	kfree(ext);
-}
-
 void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
 {
 	struct nf_ct_ext *old, *new;
@@ -114,7 +108,7 @@ void *__nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
 					(void *)old + old->offset[i]);
 			rcu_read_unlock();
 		}
-		call_rcu(&old->rcu, __nf_ct_ext_free_rcu);
+		kfree_rcu(old, rcu);
 		ct->ext = new;
 	}