Re: [PATCH v3 net-next 03/11] net: switchdev: remove the transaction structure from port object notifiers

[Ido Schimmel <idosch@idosch.org>]

On Thu, Jan 07, 2021 at 01:18:22PM +0200, Vladimir Oltean wrote:
> On Thu, Jan 07, 2021 at 12:38:35PM +0200, Ido Schimmel wrote:
> > +Petr
> > 
> > On Thu, Jan 07, 2021 at 01:17:20AM +0200, Vladimir Oltean wrote:
> > >  static int mlxsw_sp_port_obj_add(struct net_device *dev,
> > >  				 const struct switchdev_obj *obj,
> > > -				 struct switchdev_trans *trans,
> > >  				 struct netlink_ext_ack *extack)
> > >  {
> > >  	struct mlxsw_sp_port *mlxsw_sp_port = netdev_priv(dev);
> > >  	const struct switchdev_obj_port_vlan *vlan;
> > > +	struct switchdev_trans trans;
> > >  	int err = 0;
> > >  
> > >  	switch (obj->id) {
> > >  	case SWITCHDEV_OBJ_ID_PORT_VLAN:
> > >  		vlan = SWITCHDEV_OBJ_PORT_VLAN(obj);
> > > -		err = mlxsw_sp_port_vlans_add(mlxsw_sp_port, vlan, trans,
> > > +
> > 
> > Got the regression results. The call to mlxsw_sp_span_respin() should be
> > placed here because it needs to be triggered regardless of the return
> > value of mlxsw_sp_port_vlans_add().
> 
> So before, mlxsw_sp_span_respin() was called right in between the
> prepare phase and the commit phase, regardless of the error value of
> mlxsw_sp_port_vlans_add. How does that work, I assume that
> mlxsw_sp_span_respin_work gets to run after the commit phase because it
> serializes using rtnl_lock()? Then why did it matter enough to schedule
> it between the prepare and commit phase in the first place?
> And what is there to do in mlxsw_sp_span_respin_work when
> mlxsw_sp_port_vlans_add returns -EOPNOTSUPP, -EBUSY, -EINVAL, -EEXIST or
> -ENOMEM?

The bridge driver will ignore -EOPNOTSUPP and actually add the VLAN on
the bridge device. See commit 9c86ce2c1ae3 ("net: bridge: Notify about
bridge VLANs") and commit ea4721751977 ("mlxsw: spectrum_switchdev:
Ignore bridge VLAN events")

Since the VLAN was successfully added on the bridge device,
mlxsw_sp_span_respin_work() should be able to resolve the egress port
for a packet that is mirrored to a gre tap and passes through the bridge
device.