Linux Ethernet Bridging - Mar 2016 - [Bridge] [PATCH] bridge: Allow set bridge ageing time when switchdev disabled

From: Haishuang Yan <yanhaishuang at cmss.chinamobile.com>
Date: Tue, 29 Mar 2016 18:48:08 +0800
> When NET_SWITCHDEV=n, switchdev_port_attr_set will return -EOPNOTSUPP,
> we should ignore this error code and continue to set the ageing time.
> 
> Signed-off-by: Haishuang Yan <yanhaishuang at cmss.chinamobile.com>
Applied and queued up for -stable, thanks.
> @@ -582,7 +582,7 @@ int br_set_ageing_time(struct net_bridge *br, u32
ageing_time)
>  	int err;
>  
>  	err = switchdev_port_attr_set(br->dev, &attr);
> -	if (err)
> +	if (err && err != -EOPNOTSUPP)
>  		return err;
>  
>  	br->ageing_time = t;
This is at least the 5th time I've had to apply a bug fix exactly like
this one.

If this doesn't convince everyone that this whole -EOPNOTSUPP
mechanism is extremely error prone, I don't know what will.

There should be only one or two strictly controlled locations that
reinterpret the return value from all of these routines that have this
special way of signalling lack of switchdev support via -EOPNOTSUPP.

It can't be spread all over the place like this, it simply does NOT work.