Re: [PATCH nf-next v3] netfilter: xtables: lightweight process control group matching

[Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

>> Thinking about this further a bit, with this separation into net/core/, you
>> would need another Kconfig, where people choose between built-in or
>> module (or none).
> 
> Just disable module support for net_cgroup_classid. I never like the cgroup
> feature that allows modular subsystems. It will be just about 100 lines of
> code, so we gain little by making it modular. Futhermore with this change,
> we can simplify include/linux/cls_cgroup.h
> 
> Moreoever cls_cgroup is the only modular cgroup subsystem, so I may even remove
> this feature from cgroup core after the change to cls_cgroup.
> 
>> With built-in you would disallow people to load/unload the
>> cgroup part during runtime. With the module, you would introduce a module
>> dependency _for each_, even if you only want to use net_cls, which sort of
>> is not what we want from a simple "cleanup".
>>

Even if it's a module, I don't think there's any dependency here, as
the only interface that cls_cgroup and netfilter_cgroup need is
task_cls_classid(), which is an inline function and doesn't involve any
EXPORT symbol.

Therefore it works even if CONFIG_CLS_CGROUP doesn't depend of
CONFIG_NET_CGROUP_CLASSID.