[LTP] Question on .needs_cgroup_ctrls for cgroupv2

[Wei Gao]

On Mon, Feb 27, 2023 at 03:58:41PM +0100, Cyril Hrubis wrote:
> Hi!
> > How to setup correct test case for cgroupv2 check? I try to put following parameter but failed.
> > 
> > struct tst_test test = {
> > 	...
> >         .needs_cgroup_ctrls = (const char *const []){ "unified", NULL },
> >         .needs_cgroup_ver = TST_CG_V2,
> > };
> > 
> > 
> > After some investigation i found cgroup_find_ctrl which called by tst_cg_require seems not implement 
> > how to check cgroupv2, the controllers has no "unified" memeber, should we add CGROUP_CTRL_MEMBER("unified", xxx)
> > into controllers?  Correct me if any misunderstanding.
> > 
> > 
> > void tst_cg_require(const char *const ctrl_name,
> >                         const struct tst_cg_opts *options)
> > {
> >         struct cgroup_ctrl *const ctrl = cgroup_find_ctrl(ctrl_name);
> 
> I think that you are misunderstanding something, controllers that are
> checked by the .needs_cgroup_ctrls and tst_cg_require() are cgroup
> controllers such as memory or cpu controller.
> 
> And unified can be the hierarchy, that means that all controllers are in
> a single mount point which is how controllers are presented in the
> cgroup V2.
> 
> You can have a mix of V1 and V2 controllers on a system and LTP library
> abstracts away all the details so that you can focus on the test logic
> rather than on how things are set up on the system. You have to start by
> specifying which controllers is the test going to use, that's the
> .needs_cgroup_ctrls array and if the test is V2 only you pass the
> TST_CG_V2 in the flags.

So .needs_cgroup_ctrls can not used anymore for ONLY V2 case?
Since i encounter "tst_cgroup.c:848: TCONF: V2 'memory' controller required, but it's mounted on V1" when i add ".needs_cgroup_ctrls = (const char *const []){ "memory", NULL }". 

If yes then i have to manual create V2 cgroup in test case?

BTW is there any example for V2 case? I try to run some case with V2 enalbed but both failed.
> 
> -- 
> Cyril Hrubis
> chrubis@suse.cz