ipv6: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Since SLOB was removed and since
commit 6c6c47b ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()"),
it is not necessary to use call_rcu when the callback only performs
kmem_cache_free. Use kfree_rcu() directly.

The changes were made using Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://patch.msgid.link/20241013201704.49576-5-Julia.Lawall@inria.fr
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/ip6_fib.c

@@ -198,16 +198,9 @@ static void node_free_immediate(struct net *net, struct fib6_node *fn)
 	net->ipv6.rt6_stats->fib_nodes--;
 }
 
-static void node_free_rcu(struct rcu_head *head)
-{
-	struct fib6_node *fn = container_of(head, struct fib6_node, rcu);
-
-	kmem_cache_free(fib6_node_kmem, fn);
-}
-
 static void node_free(struct net *net, struct fib6_node *fn)
 {
-	call_rcu(&fn->rcu, node_free_rcu);
+	kfree_rcu(fn, rcu);
 	net->ipv6.rt6_stats->fib_nodes--;
 }