Re: [PATCH 5/7 net-next] vxlan: add VXLAN_NL2FLAG macro

[Michal Kubecek]

On Thu, Aug 27, 2020 at 08:50:19AM +0200, Fabian Frederick wrote:
> Replace common flag assignment with a macro.
> This could yet be simplified with changelink/supported but it would
> remove clarity
> 
> Signed-off-by: Fabian Frederick <fabf@xxxxxxxxx>
> ---
[...]
> diff --git a/include/net/vxlan.h b/include/net/vxlan.h
> index 3a41627cbdfe5..8a56b7a0f75f9 100644
> --- a/include/net/vxlan.h
> +++ b/include/net/vxlan.h
> @@ -290,6 +290,16 @@ struct vxlan_dev {
>  					 VXLAN_F_UDP_ZERO_CSUM6_RX |	\
>  					 VXLAN_F_COLLECT_METADATA)
>  
> +
> +#define VXLAN_NL2FLAG(iflag, flag, changelink, changelink_supported) {   \
> +	if (data[iflag]) {						 \
> +		err = vxlan_nl2flag(conf, data, iflag, flag, changelink, \
> +				    changelink_supported, extack);       \
> +		if (err)						 \
> +			return err;					 \
> +	}								 \
> +}
> +

Hiding a goto or return in a macro is generally discouraged as it may
confuse people reading or updating the code. See e.g. commit
94f826b8076e ("net: fix a potential rcu_read_lock() imbalance in
rt6_fill_node()") for an example of such problem - which was likely the
trigger for removal of NLA_PUT() and related macros shortly after.

Michal

>  struct net_device *vxlan_dev_create(struct net *net, const char *name,
>  				    u8 name_assign_type, struct vxlan_config *conf);
>  
> -- 
> 2.27.0
>