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

Jiri Pirko
2014-11-26T10:26:50Z

Wed, Nov 26, 2014 at 02:48:04AM CET, sfeldma@gmail.com wrote:
>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.

Yep, I agree this is a good idea and I also vote for implemeting this as
a follow-up. Thanks.

>
>>
>>> > + 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.