[PATCH v1 net-next 2/2] pfcp: Support per-netns netdev unregistration.

[Kuniyuki Iwashima <kuniyu@google.com>]

pfcp_net_exit_rtnl() iterates pfcp 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 pfcp_net_exit_rtnl() queues a cross-netns pfcp device,
pfcp_dellink() could be called concurrently for it (once RTNL is
removed).  In such a case, __rtnl_net_unlock() will perform the
unregistration.

We can see pfcp0 below is unregistered by the per-netns work
instead of cleanup_net().

  # bpftrace -e '#include <linux/netdevice.h>
  kprobe:pfcp_dev_uninit {
      $dev = (struct net_device *)arg0;
      printf("PID: %d | DEV: %s%s\n", pid, $dev->name, kstack());
  }
  kprobe:pfcp_net_exit_rtnl {
      printf("PID: %d%s\n", pid, kstack());
  }' &

  # ip netns add ns1
  # ip netns add ns2
  # ip -n ns1 link add pfcp0 link-netns ns2 type pfcp
  # ip netns del ns2

  PID: 12
          pfcp_net_exit_rtnl+5
          ops_undo_list+702
          cleanup_net+1122
          process_scheduled_works+2538
  ...
  PID: 462 | DEV: pfcp0
          pfcp_dev_uninit+5
          unregister_netdevice_many_notify+7129
          unregister_netdevice_many_net+1050
          rtnl_net_work_func+136
          process_scheduled_works+2538

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 drivers/net/pfcp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/pfcp.c b/drivers/net/pfcp.c
index 45f9c5d3cb20..e1cca779d2ec 100644
--- a/drivers/net/pfcp.c
+++ b/drivers/net/pfcp.c
@@ -227,12 +227,13 @@ static int pfcp_newlink(struct net_device *dev,
 	return err;
 }
 
-static void __pfcp_dellink(struct net_device *dev, struct list_head *head)
+static void __pfcp_dellink(struct net *net, struct net_device *dev,
+			   struct list_head *head)
 {
 	struct pfcp_dev *pfcp = netdev_priv(dev);
 
-	list_del(&pfcp->list);
-	unregister_netdevice_queue(dev, head);
+	list_del_init(&pfcp->list);
+	unregister_netdevice_queue_net(net, dev, head);
 }
 
 static void pfcp_dellink(struct net_device *dev, struct list_head *head)
@@ -243,7 +244,8 @@ static void pfcp_dellink(struct net_device *dev, struct list_head *head)
 	pn = net_generic(pfcp->net, pfcp_net_id);
 
 	mutex_lock(&pn->lock);
-	__pfcp_dellink(dev, head);
+	if (!list_empty(&pfcp->list))
+		__pfcp_dellink(dev_net(dev), dev, head);
 	mutex_unlock(&pn->lock);
 }
 
@@ -274,7 +276,7 @@ static void __net_exit pfcp_net_exit_rtnl(struct net *net,
 	mutex_lock(&pn->lock);
 
 	list_for_each_entry_safe(pfcp, pfcp_next, &pn->pfcp_dev_list, list)
-		__pfcp_dellink(pfcp->dev, dev_to_kill);
+		__pfcp_dellink(net, pfcp->dev, dev_to_kill);
 
 	mutex_unlock(&pn->lock);
 }
-- 
2.55.0.571.g244d577d93-goog