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

Nikolay Aleksandrov
2022-02-15T10:13:07Z

On 15/02/2022 11:54, Vladimir Oltean wrote:
> 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.
>

Hence the wrappers for commit == false and commit == true. You could name the precommit
one __vlan_flags_would_change or something more appropriate. The point is to make
sure we always update both when flags are changed.

>>>
>>> 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.