Re: [PATCH net 4/4] selftests: bonding: add a test for VLAN propagation over a bonded real device

[Stanislav Fomichev <sdf.kernel@gmail.com>]

On 06/24, Jakub Kicinski wrote:
> Add a regression test for the VLAN notifier handling that the netdev_work
> deferral fixed.
> 
> A VLAN's real device propagates its UP/DOWN, MTU and feature changes onto
> the VLANs stacked on top of it. This used to be done synchronously from the
> real device's notifier and deadlocked when the real device was brought up
> while enslaved to a bond (instance lock held across NETDEV_UP) and the VLAN
> on top was itself a bond member: the synchronous propagation re-entered the
> stack and took the same instance lock again.
> 
> The test covers both halves:
>  - that the deferred UP/DOWN, MTU and feature propagation actually lands on
>    the VLAN (link state and MTU use an ops-locked dummy, i.e. the deferral
>    path; features use veth, which exports vlan_features to inherit), and
>  - that the deadlock-prone topology - a VLAN on a dummy, with the VLAN and
>    the dummy each enslaved to a different bond - can be built without
>    hanging.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Acked-by: Stanislav Fomichev <sdf@fomichev.me>