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

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Date:	Tue, 25 Nov 2014 15:48:04 -1000
From:	Scott Feldman <sfeldma@...il.com>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	Andy Gospodarek <gospo@...ulusnetworks.com>,
	Jiri Pirko <jiri@...nulli.us>, Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	"nhorman@...driver.com" <nhorman@...driver.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	"dborkman@...hat.com" <dborkman@...hat.com>,
	"ogerlitz@...lanox.com" <ogerlitz@...lanox.com>,
	"jesse@...ira.com" <jesse@...ira.com>,
	"pshelar@...ira.com" <pshelar@...ira.com>,
	"azhou@...ira.com" <azhou@...ira.com>,
	"ben@...adent.org.uk" <ben@...adent.org.uk>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"vyasevic@...hat.com" <vyasevic@...hat.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	"Fastabend, John R" <john.r.fastabend@...el.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	John Linville <linville@...driver.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	"ryazanov.s.a@...il.com" <ryazanov.s.a@...il.com>,
	"buytenh@...tstofly.org" <buytenh@...tstofly.org>,
	Aviad Raveh <aviadr@...lanox.com>,
	"nbd@...nwrt.org" <nbd@...nwrt.org>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Neil Jerram <Neil.Jerram@...aswitch.com>,
	"ronye@...lanox.com" <ronye@...lanox.com>,
	"simon.horman@...ronome.com" <simon.horman@...ronome.com>,
	"alexander.h.duyck@...hat.com" <alexander.h.duyck@...hat.com>,
	"Ronciak, John" <john.ronciak@...el.com>,
	"mleitner@...hat.com" <mleitner@...hat.com>,
	Shrijeet Mukherjee <shrijeet@...il.com>,
	Benjamin LaHaise <bcrl@...ck.org>
Subject: Re: [patch net-next v3 09/17] bridge: add API to notify bridge driver
 of learned FBD on offloaded device

On Tue, Nov 25, 2014 at 12:36 PM, Thomas Graf <tgraf@...g.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@...il.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@...il.com>
>> > Signed-off-by: Jiri Pirko <jiri@...nulli.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.
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