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 11:20:07 +0000

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.

>  
>  	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
>