Re: [PATCH v4 net 2/2] net: bridge: switchdev: Ensure deferred event delivery on unoffload

[Vladimir Oltean <olteanv@gmail.com>]

On Mon, Feb 12, 2024 at 08:18:44PM +0100, Tobias Waldekranz wrote:
> When unoffloading a device, it is important to ensure that all
> relevant deferred events are delivered to it before it disassociates
> itself from the bridge.
> 
> Before this change, this was true for the normal case when a device
> maps 1:1 to a net_bridge_port, i.e.
> 
>    br0
>    /
> swp0
> 
> When swp0 leaves br0, the call to switchdev_deferred_process() in
> del_nbp() makes sure to process any outstanding events while the
> device is still associated with the bridge.
> 
> In the case when the association is indirect though, i.e. when the
> device is attached to the bridge via an intermediate device, like a
> LAG...
> 
>     br0
>     /
>   lag0
>   /
> swp0
> 
> ...then detaching swp0 from lag0 does not cause any net_bridge_port to
> be deleted, so there was no guarantee that all events had been
> processed before the device disassociated itself from the bridge.
> 
> Fix this by always synchronously processing all deferred events before
> signaling completion of unoffloading back to the driver.
> 
> Fixes: 4e51bf44a03a ("net: bridge: move the switchdev object replay helpers to "push" mode")
> Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
> ---

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>