Re: [patch net-next v3 09/17] bridge: add API to notify bridge driver of learned FBD on offloaded device

Scott Feldman
2014-11-26T01:48:06Z

On Tue, Nov 25, 2014 at 12:36 PM, Thomas Graf <tgraf@suug.ch> wrote:
> On 11/25/14 at 11:38am, Andy Gospodarek wrote:
>> On Tue, Nov 25, 2014 at 11:28:40AM +0100, Jiri Pirko wrote:
>> > From: Scott Feldman <sfeldma@gmail.com>
>> >
>> > When the swdev device learns a new mac/vlan on a port, it sends some async
>> > notification to the driver and the driver installs an FDB in the device.
>> > To give a holistic system view, the learned mac/vlan should be reflected
>> > in the bridge's FBD table, so the user, using normal iproute2 cmds, can view
>> > what is currently learned by the device. This API on the bridge driver gives
>> > a way for the swdev driver to install an FBD entry in the bridge FBD table.
>> > (And remove one).
>> >
>> > This is equivalent to the device running these cmds:
>> >
>> > bridge fdb [add|del] <mac> dev <dev> vid <vlan id> master
>> >
>> > This patch needs some extra eyeballs for review, in paricular around the
>> > locking and contexts.
>> >
>> > Signed-off-by: Scott Feldman <sfeldma@gmail.com>
>> > Signed-off-by: Jiri Pirko <jiri@resnulli.us>
>
> I like the simplicity of this. That said, given we'll have multiple
> users of swdev including OVS, shouldn't this be a notifier or a
> callback that depends on who is controlling the device?

I like the idea. When the switch port joins Linux bridge or OVS
datapath, a callback is registered with the driver. That way the
driver doesn't really care if the port is a bridge member or an OVS
vport in a datapath. It's just passing up the FDB entry
(port/mac/vlan) details to the container device. Can we hold this
idea until this patchset sticks? I think once OVS support comes back
into the swdev model would be the time to address this.

>
>> > + spin_lock(&br->hash_lock);
>> (Since you asked to check locking...)
>>
>> Most of the other fdb_add/delete/insert/update calls take this with
>> spin_lock_bh. Did you try this with lockdep enabled just to see if that
>> is needed here? I suspect that anytime br->hash_lock is taken it will
>> need to be with softirqs disabled from this point forward.
>
> At least br_fdb_update() seems to be called from BH context so I would
> agree and argue the lock in br_fdb_cleanup() and br_fdb_update() need a
> fix too. I'll send a patch.