linux-kernel - Re: [PATCH 2/3] bridge: trigger a bridge calculation upon port changes

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Message-ID: <20140422194313.GQ27882@wotan.suse.de>
Date:	Tue, 22 Apr 2014 21:43:13 +0200
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
Cc:	Cong Wang <cwang@...pensource.com>,
	netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
	Stephen Hemminger <stephen@...workplumber.org>,
	bridge@...ts.linux-foundation.org
Subject: Re: [PATCH 2/3] bridge: trigger a bridge calculation upon port
	changes

On Tue, Mar 18, 2014 at 02:22:43PM -0700, Luis R. Rodriguez wrote:
> On Tue, Mar 18, 2014 at 01:46:49PM -0700, Cong Wang wrote:
> > On Fri, Mar 14, 2014 at 6:39 PM, Luis R. Rodriguez <mcgrof@...e.com> wrote:
> > > On Thu, Mar 13, 2014 at 11:26:25AM -0700, Cong Wang wrote:
> > >> On Wed, Mar 12, 2014 at 8:15 PM, Luis R. Rodriguez
> > >> <mcgrof@...not-panic.com> wrote:
> > >> >                         spin_unlock_bh(&p->br->lock);
> > >> > +                       if (changed)
> > >> > +                               call_netdevice_notifiers(NETDEV_CHANGEADDR,
> > >> > +                                                        p->br->dev);
> > >> > +                       netdev_update_features(p->br->dev);
> > >>
> > >> I think this is supposed to be in netdev event handler of br->dev
> > >> instead of here.
> > >
> > > Do you mean netdev_update_features() ? I mimic'd what was being done on
> > > br_del_if() given that root blocking is doing something similar. If
> > > we need to change something for the above then I suppose it means we need
> > > to change br_del_if() too. Let me know if you see any reason for something
> > > else.
> > >
> > 
> > Yeah, for me it looks like it's better to call netdev_update_features()
> > in the event handler of br->dev, rather than where calling
> > call_netdevice_notifiers(..., br->dev);.
> 
> I still don't see why, in fact trying to verify this I am wondering now
> if instead we should actually fix br_features_recompute() to take into
> consideration BR_ROOT_BLOCK as below. Notice how netdev_update_features()
> is called above even if the MAC address did not change, just as is done
> on br_del_if(). There is an NETDEV_FEAT_CHANGE event so would it be more
> appropriate we just call
> 
> call_netdevice_notifiers(NETDEV_FEAT_CHANGE, p->br->dev)
> 
> for both the above then and also br_del_if()? How about the below
> change?
> 
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index 54d207d..dcd9378 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -315,6 +315,8 @@ netdev_features_t br_features_recompute(struct net_bridge *br,
>  	features &= ~NETIF_F_ONE_FOR_ALL;
>  
>  	list_for_each_entry(p, &br->port_list, list) {
> +		if (p->flags & BR_ROOT_BLOCK)
> +			continue;
>  		features = netdev_increment_features(features,
>  						     p->dev->features, mask);
>  	}

Cong, can you provide feedback on this? I tried to grow confidence on the
hunk above but its not clear but the other points still hold and I'd love
your feedback on those.

  Luis
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