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

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 <kuniyu@google.com>
---
 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);
 	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);
 
 	mutex_unlock(&gn->lock);
 }

-- 
2.55.0.571.g244d577d93-goog