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

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Message-ID: <20210107141349.GA1130184@shredder.lan>
Date:   Thu, 7 Jan 2021 16:13:49 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     petrm@...dia.com, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vadym Kochan <vkochan@...vell.com>,
        Taras Chornyi <tchornyi@...vell.com>,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Ivan Vecera <ivecera@...hat.com>
Subject: Re: [PATCH v3 net-next 03/11] net: switchdev: remove the transaction
 structure from port object notifiers

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.