[net-next PATCH] macvlan: resolve ENOENT errors on creation

[John Fastabend <john.fastabend@gmail.com>]

After the commit below attempting to create macvlan devices was
resulting in ENOENT errors,

# ip link add link p3p2 type macvlan
RTNETLINK answers: Invalid argument

This happens because netdev_upper_dev_link() is called before
register_netdevice() in the macvlan code. Through a call chain
this results in a call to __netdev_adjacent_dev_insert() and
finally a sysfs_create_link(). This requires the kobject of
the macvlan to be registered which is done in register_netdevice().
If there is no kobject which is the case here the ENOENT error
is seen on the command line.

To resolve this move the netdev_upper_dev_link() call below
the register_netdevice() call. This aligns with vlan driver
flow.

Regression introduced here,

commit 5831d66e8097aedfa3bc35941cf265ada2352317
Author: Veaceslav Falico <vfalico@redhat.com>
Date:   Wed Sep 25 09:20:32 2013 +0200

    net: create sysfs symlinks for neighbour devices

CC: Veaceslav Falico <vfalico@redhat.com>
CC: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
---
 drivers/net/macvlan.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 9bf46bd..cc9845e 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -828,22 +828,21 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
 		eth_hw_addr_inherit(dev, lowerdev);
 	}
 
+	port->count += 1;
+	err = register_netdevice(dev);
+	if (err < 0)
+		goto destroy_port;
+
 	err = netdev_upper_dev_link(lowerdev, dev);
 	if (err)
 		goto destroy_port;
 
-	port->count += 1;
-	err = register_netdevice(dev);
-	if (err < 0)
-		goto upper_dev_unlink;
 
 	list_add_tail_rcu(&vlan->list, &port->vlans);
 	netif_stacked_transfer_operstate(lowerdev, dev);
 
 	return 0;
 
-upper_dev_unlink:
-	netdev_upper_dev_unlink(lowerdev, dev);
 destroy_port:
 	port->count -= 1;
 	if (!port->count)