Subject: Re: [PATCH net-next 7/9] net: bridge: Stop calling switchdev_port_attr_get()

From: Ido Schimmel <[email-masked]>
Date: Thu, 14 Feb 2019 13:02:04 +0000

On Thu, Feb 14, 2019 at 01:20:02PM +0200, Ido Schimmel wrote:
> On Wed, Feb 13, 2019 at 02:06:36PM -0800, Florian Fainelli wrote:
> > Now that all switchdev drivers have been converted to checking the
> > bridge port flags during the prepare phase of the
> > switchdev_port_attr_set() when the process
> > SWITCHDEV_ATTR_ID_PORT_PRE_BRIDGE_FLAGS, we can avoid calling
> > switchdev_port_attr_get() with
> > SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS_SUPPORT.
> > 
> > Signed-off-by: Florian Fainelli <[email-masked]>
> > ---
> >  net/bridge/br_switchdev.c | 16 +++++++---------
> >  1 file changed, 7 insertions(+), 9 deletions(-)
> > 
> > diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
> > index db9e8ab96d48..8f88f8a1a7fa 100644
> > --- a/net/bridge/br_switchdev.c
> > +++ b/net/bridge/br_switchdev.c
> > @@ -64,29 +64,27 @@ int br_switchdev_set_port_flag(struct net_bridge_port *p,
> >  {
> >  	struct switchdev_attr attr = {
> >  		.orig_dev = p->dev,
> > -		.id = SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS_SUPPORT,
> > +		.id = SWITCHDEV_ATTR_ID_PORT_PRE_BRIDGE_FLAGS,
> > +		.u.brport_flags = flags,
> >  	};
> >  	int err;
> >  
> >  	if (mask & ~BR_PORT_FLAGS_HW_OFFLOAD)
> >  		return 0;
> >  
> > -	err = switchdev_port_attr_get(p->dev, &attr);
> > -	if (err == -EOPNOTSUPP)
> > -		return 0;
> > -	if (err)
> > +	err = switchdev_port_attr_set(p->dev, &attr);
> > +	if (err && err != -EOPNOTSUPP)
> >  		return err;
> >  
> > -	/* Check if specific bridge flag attribute offload is supported */
> > -	if (!(attr.u.brport_flags_support & mask)) {
> > +	if (err == -EOPNOTSUPP) {
> >  		br_warn(p->br, "bridge flag offload is not supported %u(%s)\n",
> >  			(unsigned int)p->port_no, p->dev->name);
> > -		return -EOPNOTSUPP;
> > +		return err;
> >  	}
> 
> I see that you return -EOPNOTSUPP from drivers in case of unsupported
> flags. I believe this is problematic (I'll test soon). The same return
> code is used by:
> 
> 1. Switch drivers to indicate unsupported flags
> 2. switchdev code to indicate unsupported netdev (no switchdev ops)
> 
> I guess that with this patch any attempt to set bridge port flags on
> veth/dummy device will result in an error.

Yea, that's the case. You can test with
tools/testing/selftests/net/forwarding/bridge_vlan_aware.sh and other
bridge-related tests we have there.

Another problem is that during PORT_PRE_BRIDGE_FLAGS you pass 'flags'
and not 'mask'. This breaks mlxsw (and probably others as well) given
BR_BCAST_FLOOD is set by default.

> 
> >  
> >  	attr.id = SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS;
> >  	attr.flags = SWITCHDEV_F_DEFER;
> > -	attr.u.brport_flags = flags;
> > +
> >  	err = switchdev_port_attr_set(p->dev, &attr);
> >  	if (err) {
> >  		br_warn(p->br, "error setting offload flag on port %u(%s)\n",
> > -- 
> > 2.17.1
> >