netdev - Re: [PATCH v3 net-next 05/15] geneve: use exit_batch

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Message-ID: <CANn89iLJrrJs+6Vc==Un4rVKcpV0Eof4F_4w1_wQGxUCE2FWAg@mail.gmail.com>
Date: Tue, 6 Feb 2024 11:22:23 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Antoine Tenart <atenart@...nel.org>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH v3 net-next 05/15] geneve: use exit_batch_rtnl() method

On Tue, Feb 6, 2024 at 10:19 AM Antoine Tenart <atenart@...nel.org> wrote:
>
> Quoting Eric Dumazet (2024-02-05 13:47:42)
> > -static void __net_exit geneve_exit_batch_net(struct list_head *net_list)
> > +static void __net_exit geneve_exit_batch_rtnl(struct list_head *net_list,
> > +                                             struct list_head *dev_to_kill)
> >  {
> >         struct net *net;
> > -       LIST_HEAD(list);
> >
> > -       rtnl_lock();
> >         list_for_each_entry(net, net_list, exit_list)
> > -               geneve_destroy_tunnels(net, &list);
> > -
> > -       /* unregister the devices gathered above */
> > -       unregister_netdevice_many(&list);
> > -       rtnl_unlock();
> > +               geneve_destroy_tunnels(net, dev_to_kill);
> >
> >         list_for_each_entry(net, net_list, exit_list) {
> >                 const struct geneve_net *gn = net_generic(net, geneve_net_id);
>
> Not shown in the diff here is:
>
>   WARN_ON_ONCE(!list_empty(&gn->sock_list));
>
> I think this will be triggered as the above logic inverted two calls,
> which are now,
>
> 1. WARN_ON_ONCE(...)
> 2. unregister_netdevice_many
>
> But ->sock_list entries are removed in ndo_exit, called from
> unregister_netdevice_many.
>
> I guess the warning could be moved to exit_batch (or removed).

I will keep the warning, but move it, thanks [1]

Speaking of geneve, I think the synchronize_net() call from
geneve_sock_release() could easily be avoided.

[1] I will squash the following delta for v4 submission.

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index f31fc52ef397dfe0eba854385f783fbcad7e870f..23e97c2e4f6fcb90a8bbb117d7520397f560f15f
100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1907,17 +1907,19 @@ static void __net_exit
geneve_exit_batch_rtnl(struct list_head *net_list,

        list_for_each_entry(net, net_list, exit_list)
                geneve_destroy_tunnels(net, dev_to_kill);
+}

-       list_for_each_entry(net, net_list, exit_list) {
-               const struct geneve_net *gn = net_generic(net, geneve_net_id);
+static void __net_exit geneve_exit_net(struct net *net)
+{
+       const struct geneve_net *gn = net_generic(net, geneve_net_id);

-               WARN_ON_ONCE(!list_empty(&gn->sock_list));
-       }
+       WARN_ON_ONCE(!list_empty(&gn->sock_list));
 }

 static struct pernet_operations geneve_net_ops = {
        .init = geneve_init_net,
        .exit_batch_rtnl = geneve_exit_batch_rtnl,
+       .exit = geneve_exit_net,
        .id   = &geneve_net_id,
        .size = sizeof(struct geneve_net),
 };