[LTP] [PATCH] tst_cgroup: Don't try to use V2 if V1 controllers are mounted

[Li Wang]

On Thu, Sep 24, 2020 at 10:06 PM Richard Palethorpe <rpalethorpe@suse.de>
wrote:

> Hello Li,
>
> Li Wang <liwang@redhat.com> writes:
>
> > Hi Richard,
> >
> > On Thu, Sep 24, 2020 at 7:11 PM Richard Palethorpe <rpalethorpe@suse.com
> >
> > wrote:
> >
> >> It is not possible to use a controller in V2 cgroups if it has been
> >> mounted as a V1 controller. So if V1 is mounted we use it regardless
> >> of if V2 is available.
> >>
> >> We have to include a space in tst_is_mounted so that we do not match
> >> cgroup2.
> >>
> >> Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
> >> ---
> >>  lib/tst_cgroup.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
> >> index ba413d874..73ddd4b82 100644
> >> --- a/lib/tst_cgroup.c
> >> +++ b/lib/tst_cgroup.c
> >> @@ -44,7 +44,7 @@ enum tst_cgroup_ver tst_cgroup_version(void)
> >>          enum tst_cgroup_ver cg_ver;
> >>
> >>          if (tst_cgroup_check("cgroup2")) {
> >> -                if (!tst_is_mounted("cgroup2") &&
> >> tst_is_mounted("cgroup"))
> >> +                if (tst_is_mounted("cgroup "))
> >>
> >
> > Add a space in the suffix still not work as expected.
> >
> > The reason is that tst_is_mounted("cgroup ") also get non-zero return if
> > system only mount cgroup_v2, which lead to choose cgroup_v1 in LTP test.
> >
> > # cat /proc/mounts |grep cgroup
> > cgroup2 /sys/fs/cgroup cgroup2 rw,seclabel,nosuid,nodev,noexec,relatime
> 0 0
>
> I wonder if it would be better to simply try mounting/using V2 and if
> that fails try V1?
>

That will be work but not good, because if cgroup mount fails, how do we
know it is a bug or not support?

-- 
Regards,
Li Wang
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