nexthop: change nexthop_net_exit() to nexthop_net_exit_batch()

cleanup_net() is competing with other rtnl users.

nexthop_net_exit() seems a good candidate for exit_batch(),
as this gives chance for cleanup_net() to progress much faster,
holding rtnl a bit longer.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reviewed-by: NDavid Ahern <dsahern@kernel.org>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

net/ipv4/nexthop.c

@@ -3733,12 +3733,16 @@ void nexthop_res_grp_activity_update(struct net *net, u32 id, u16 num_buckets,
 }
 EXPORT_SYMBOL(nexthop_res_grp_activity_update);
 
-static void __net_exit nexthop_net_exit(struct net *net)
+static void __net_exit nexthop_net_exit_batch(struct list_head *net_list)
 {
+	struct net *net;
+
 	rtnl_lock();
-	flush_all_nexthops(net);
+	list_for_each_entry(net, net_list, exit_list) {
+		flush_all_nexthops(net);
+		kfree(net->nexthop.devhash);
+	}
 	rtnl_unlock();
-	kfree(net->nexthop.devhash);
 }
 
 static int __net_init nexthop_net_init(struct net *net)
@@ -3756,7 +3760,7 @@ static int __net_init nexthop_net_init(struct net *net)
 
 static struct pernet_operations nexthop_net_ops = {
 	.init = nexthop_net_init,
-	.exit = nexthop_net_exit,
+	.exit_batch = nexthop_net_exit_batch,
 };
 
 static int __init nexthop_init(void)