[CRIU] [PATCH] Skip restoring the cgroup root directories when using full mode

[Hui Kang]

Hi, Cyrill
To provide more information about this patch.

>From the cgroup.c, I see that if the restoring stratgy is full, it will
always restore all the cgroup properties, which includes
/sys/fs/cgroup/cpusets.cpu. As that file is not write-able by criu (i.e.,
echo "1024" > /sys/fs/cgroup/cpusets.cpu fails), it will cause problem.

In contrast, when restoring with "soft" mode, the e->n_properties is zero
so that restore_cgroup_prop() is not called.

- Hui

On Wed, Aug 12, 2015 at 6:00 PM, Cyrill Gorcunov <gorcunov at gmail.com> wrote:

> On Wed, Aug 12, 2015 at 05:37:35PM -0400, Hui Kang wrote:
> >
> >      Could you please explain how we end up having empty dir_name here?
> >
> >    This happens when restoring a process with cgroup using
> >    --manage-cgroup=full.
> >    To reproduce this error
> >    1. start a process
> >    2. mkdir /sys/fs/cgroups/cpusets/foo
> >    3. echo PID > /sys/fs/cgroups/cpusets/foo/tasks
> >    4. checkpoint the process
> >    5. rmdir /sys/fs/cgroups/cpusets/foo or copy the checkedpoint images
> to a
> >    different host
> >    5. /root/criu/criu restore --log-file ./restore.log -vvvv -j
> >    --manage-cgroup=full
>
> Hmm. Thanks for info! Need to think...
>
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