Re: [PATCH v1 net-next 3/3] geneve: Support per-netns netdev unregistration.

On Tue, Aug 4, 2026 at 10:34 AM Paolo Abeni <[email protected]> wrote:
>
> On 8/4/26 5:24 PM, Kuniyuki Iwashima wrote:
> > On Tue, Aug 4, 2026 at 6:47 AM Paolo Abeni <[email protected]> wrote:
> >> On 7/31/26 6:45 PM, Kuniyuki Iwashima wrote:
> >>> geneve_exit_rtnl_net() iterates geneve devices whose sockets
> >>> are in the dying netns and queues them for destruction.
> >>>
> >>> So the devices may reside in different netns.
> >>>
> >>> Let's use unregister_netdevice_queue_net() to support per-netns
> >>> device unregistration.
> >>>
> >>> list_del() is changed to list_del_init() to avoid queueing the
> >>> same device twice.
> >>>
> >>> Even after geneve_exit_rtnl_net() queues a cross-netns geneve
> >>> device, geneve_dellink() can be called concurrently for it.
> >>> In such a case, __rtnl_net_unlock() will perform the unregistration.
> >>>
> >>> Note that geneve uses register_pernet_subsys() instead of _device(),
> >>> so default_device_exit_batch() guarantees that the async per-netns
> >>> works are flushed before ->exit().
> >>>
> >>> Tested:
> >>>
> >>> 1. Create geneve device across two netns.
> >>>
> >>>   # ip netns add ns1
> >>>   # ip netns add ns2
> >>>   # ip -n ns1 link add geneve0 link-netns ns2 type geneve external
> >>>
> >>> 2. Run bpftrace to check that geneve_uninit() is called between
> >>>    ->exit_rtnl() and ->exit().
> >>>
> >>>   # bpftrace -e '#include <linux/netdevice.h>
> >>>   kprobe:geneve_uninit {
> >>>       $dev = (struct net_device *)arg0;
> >>>       printf("PID: %d | DEV: %s%s\n", pid, $dev->name, kstack());
> >>>   }
> >>>   kprobe:geneve_exit_rtnl_net,
> >>>   kprobe:geneve_exit_net {
> >>>       printf("PID: %d%s\n", pid, kstack());
> >>>   }'
> >>>
> >>> 3. Remove the netns where the geneve socket resides
> >>>
> >>>   # ip netns del ns2
> >>>
> >>> Now, we can see geneve0 is unregistered by per-netns work
> >>> instead of cleanup_net() and it finishes before ->exit() to
> >>> avoid WARN_ON_ONCE(!list_empty(&gn->sock_list)) there.
> >>>
> >>>   PID: 571
> >>>           geneve_exit_rtnl_net+5
> >>>           ops_undo_list+702
> >>>           cleanup_net+1122
> >>>           process_scheduled_works+2538
> >>>   ...
> >>>   PID: 1047 | DEV: geneve0
> >>>           geneve_uninit+5
> >>>           unregister_netdevice_many_notify+7129
> >>>           unregister_netdevice_many_net+1050
> >>>           rtnl_net_work_func+136
> >>>           process_scheduled_works+2538
> >>>   ...
> >>>   PID: 571
> >>>           geneve_exit_net+5
> >>>           ops_undo_list+1064
> >>>           cleanup_net+1122
> >>>           process_scheduled_works+2538
> >>>   ...
> >>>
> >>> Signed-off-by: Kuniyuki Iwashima <[email protected]>
> >>> ---
> >>>  drivers/net/geneve.c | 12 +++++++-----
> >>>  1 file changed, 7 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
> >>> index f456a85dca77..a6a8978e3b81 100644
> >>> --- a/drivers/net/geneve.c
> >>> +++ b/drivers/net/geneve.c
> >>> @@ -2502,12 +2502,13 @@ static int geneve_changelink(struct net_device *dev, struct nlattr *tb[],
> >>>       return err;
> >>>  }
> >>>
> >>> -static void __geneve_dellink(struct net_device *dev, struct list_head *head)
> >>> +static void __geneve_dellink(struct net *net, struct net_device *dev,
> >>> +                          struct list_head *head)
> >>>  {
> >>>       struct geneve_dev *geneve = netdev_priv(dev);
> >>>
> >>> -     list_del(&geneve->next);
> >>> -     unregister_netdevice_queue(dev, head);
> >>> +     list_del_init(&geneve->next);
> >>> +     unregister_netdevice_queue_net(net, dev, head);
> >>>  }
> >>>
> >>>  static void geneve_dellink(struct net_device *dev, struct list_head *head)
> >>> @@ -2518,7 +2519,8 @@ static void geneve_dellink(struct net_device *dev, struct list_head *head)
> >>>       gn = net_generic(geneve->net, geneve_net_id);
> >>>
> >>>       mutex_lock(&gn->lock);
> >>> -     __geneve_dellink(dev, head);
> >>> +     if (!list_empty(&geneve->next))
> >>> +             __geneve_dellink(dev_net(dev), dev, head);
> >>
> >> Sashiko noted that the lockdep chain between dev->lock, utn->loc and
> >> gn->lock is not trivial, possibly a documentation follow-up would be useful
> >>
> >>>       mutex_unlock(&gn->lock);
> >>>  }
> >>>
> >>> @@ -2754,7 +2756,7 @@ static void __net_exit geneve_exit_rtnl_net(struct net *net,
> >>>       mutex_lock(&gn->lock);
> >>>
> >>>       list_for_each_entry_safe(geneve, next, &gn->geneve_list, next)
> >>> -             __geneve_dellink(geneve->dev, dev_to_kill);
> >>> +             __geneve_dellink(net, geneve->dev, dev_to_kill);
> >>
> >> Here sashiko foresees some problem with CONFIG_DEBUG_NET_SMALL_RTNL
> >> before full conversion to per netns lock even of ovs. Just more
> >> follow-up, I guess.
> >
> > Is it Sashiko-nipa output ?
>
> Yes, sorry I should have included the link:
>
> https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260731164612.2148830-1-kuniyu%40google.com
>
> sometimes PW reports a timeout, but the report is still available via
> the sashiko nipa UI.

Ah, good to know that, I gave up looking for it due to the timeout log.

Thanks !


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>
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