Linux Ethernet Bridging - Jul 2021 - [Bridge] [PATCH v5 net-next 00/10] Let switchdev drivers offload and unoffload bridge ports at their own convenience

On Tue, Jul 20, 2021 at 02:12:01PM +0000, Vladimir Oltean
wrote:
> On Tue, Jul 20, 2021 at 05:01:48PM +0300, Ido Schimmel wrote:
> > > The patches were split from a larger series for easier review:
> > 
> > This is not what I meant. I specifically suggested to get the TX
> > forwarding offload first and then extending the API with an argument
to
> > opt-in for the replay / cleanup:
> 
> Yeah, ok, I did not get that and I had already reposted by the time you
> clarified, sorry.
> 
> Anyway, is it so bad that we cannot look at the patches in the order
> that they are in right now (even if this means that maybe a few more
> days would pass)? To me it makes a bit more sense anyway to first
> consolidate the code that is already in the tree right now, before
> adding new logic. And I don't really want to rebase the patches again
to
> change the ordering and risk a build breakage without a good reason.
If you don't want to change the order, then at least make the
replay/cleanup optional and set it to 'false' for mlxsw. This should
mean that the only change in mlxsw should be adding calls to
switchdev_bridge_port_offload() / switchdev_bridge_port_unoffload() in
mlxsw_sp_bridge_port_create() / mlxsw_sp_bridge_port_destroy(),
respectively.

On Tue, Jul 20, 2021 at 05:25:08PM +0300, Ido Schimmel
wrote:
> If you don't want to change the order, then at least make the
> replay/cleanup optional and set it to 'false' for mlxsw. This
should
> mean that the only change in mlxsw should be adding calls to
> switchdev_bridge_port_offload() / switchdev_bridge_port_unoffload() in
> mlxsw_sp_bridge_port_create() / mlxsw_sp_bridge_port_destroy(),
> respectively.
I mean, I could guard br_{vlan,mdb,fdb}_replay() against NULL notifier
block pointers, and then make mlxsw pass NULL for both the atomic_nb and
blocking_nb.

But why? How do you deal with a host-joined mdb that was auto-installed
while there was no port under the bridge? How does anyone deal with
that? What's optional about it? Why would driver X opt out of it but Y
not (apart for the case where driver X does not offload MDBs at all,
that I can understand).

On Tue, Jul 20, 2021 at 05:25:08PM +0300, Ido Schimmel
wrote:
> If you don't want to change the order, then at least make the
> replay/cleanup optional and set it to 'false' for mlxsw. This
should
> mean that the only change in mlxsw should be adding calls to
> switchdev_bridge_port_offload() / switchdev_bridge_port_unoffload() in
> mlxsw_sp_bridge_port_create() / mlxsw_sp_bridge_port_destroy(),
> respectively.
Is there any specific reason why you suggested me to move the
switchdev_bridge_port_offload() call from the top-level
mlxsw_sp_port_bridge_join() into mlxsw_sp_bridge_port_create()
(and similarly, from _pre_bridge_leave to _destroy)?

Even if you don't support replays right now, you'd need to move a bunch
of code around before you would get them to work. As far as I can see,
mlxsw_sp_bridge_port_create() is a bit too early and
mlxsw_sp_bridge_port_destroy() is a bit too late. The port needs to be
fairly up and running to be able to process the switchdev notifiers at
that stage.

Do you mind if I keep the hooks where they are, which is what I do for
all drivers? I don't think I am missing to handle any case.