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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Message-ID: <20141125223643.GH3912@casper.infradead.org>
Date:	Tue, 25 Nov 2014 22:36:43 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Andy Gospodarek <gospo@...ulusnetworks.com>
Cc:	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
	davem@...emloft.net, nhorman@...driver.com, andy@...yhouse.net,
	dborkman@...hat.com, ogerlitz@...lanox.com, jesse@...ira.com,
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	stephen@...workplumber.org, jeffrey.t.kirsher@...el.com,
	vyasevic@...hat.com, xiyou.wangcong@...il.com,
	john.r.fastabend@...el.com, edumazet@...gle.com, jhs@...atatu.com,
	sfeldma@...il.com, f.fainelli@...il.com, roopa@...ulusnetworks.com,
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	alexander.h.duyck@...hat.com, john.ronciak@...el.com,
	mleitner@...hat.com, shrijeet@...il.com, 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 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?

> > +	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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