Re: [PATCH v2 net-next 1/8] net: bridge: vlan: notify switchdev only when something changed

Vladimir Oltean
2022-02-15T09:54:12Z

On Tue, Feb 15, 2022 at 10:54:26AM +0200, Nikolay Aleksandrov wrote:
> > +/* return true if anything will change as a result of __vlan_add_flags,
> > + * false otherwise
> > + */
> > +static bool __vlan_flags_would_change(struct net_bridge_vlan *v, u16 flags)
> > +{
> > + struct net_bridge_vlan_group *vg;
> > + u16 old_flags = v->flags;
> > + bool pvid_changed;
> >
> > - return ret || !!(old_flags ^ v->flags);
> > + if (br_vlan_is_master(v))
> > + vg = br_vlan_group(v->br);
> > + else
> > + vg = nbp_vlan_group(v->port);
> > +
> > + if (flags & BRIDGE_VLAN_INFO_PVID)
> > + pvid_changed = (vg->pvid == v->vid);
> > + else
> > + pvid_changed = (vg->pvid != v->vid);
> > +
> > + return pvid_changed || !!(old_flags ^ v->flags);
> > }
>
> These two have to depend on each other, otherwise it's error-prone and
> surely in the future someone will forget to update both.
> How about add a "commit" argument to __vlan_add_flags and possibly rename
> it to __vlan_update_flags, then add 2 small helpers like __vlan_update_flags_precommit
> with commit == false and __vlan_update_flags_commit with commit == true.
> Or some other naming, the point is to always use the same flow and checks
> when updating the flags to make sure people don't forget.

You want to squash __vlan_flags_would_change() and __vlan_add_flags()
into a single function? But "would_change" returns bool, and "add"
returns void.

> >
> > static int __vlan_vid_add(struct net_device *dev, struct net_bridge *br,
> > @@ -672,9 +685,13 @@ static int br_vlan_add_existing(struct net_bridge *br,
> > {
> > int err;
> >
> > - err = br_switchdev_port_vlan_add(br->dev, vlan->vid, flags, extack);
> > - if (err && err != -EOPNOTSUPP)
> > - return err;
> > + *changed = __vlan_flags_would_change(vlan, flags);
> > + if (*changed) {
> > + err = br_switchdev_port_vlan_add(br->dev, vlan->vid, flags,
> > + extack);
> > + if (err && err != -EOPNOTSUPP)
> > + return err;
> > + }
>
> You should revert *changed to false in the error path below,
> otherwise we will emit a notification without anything changed
> if the br_vlan_is_brentry(vlan)) { } block errors out.

Ok.