[CRIU] [PATCH 1/2] finalize cgroups correctly

[Saied Kazemi]

On Tue, Mar 24, 2015 at 10:57 AM, Pavel Emelyanov <xemul at parallels.com>
wrote:

> On 03/24/2015 08:25 PM, Saied Kazemi wrote:
> > For the easy case of comparing pathname strings on the command line (-D
> and --root), I
> > think it's better to error and exit instead of restoring with all the
> cgyard mounts
> > leaked into the restored process tree.
>
> I rather agree with this. It's quite uncommon (from my perspective) that
> images sit
> in the container's root, so preventing this usage doesn't (shouldn't)
> break anything
> critical. Does it?
>

It wouldn't break anything because nothing has been merged yet.



> > For a more general solution, is it possible to make sure that after
> fini_cgroup() the
> > cgyard mount points have been successfully removed from the restored
> tree?
>
> What if we call umount with detach flag on cgyard dir inside
> restore_task_mnt_ns()?
> Would this resolve this?
>

I just quickly tried the following patch, first calling umount_cgyard()
before if and then after if.  Neither case worked :(

--Saied

diff --git a/cgroup.c b/cgroup.c
index b1a2f92..fa94853 100644
--- a/cgroup.c
+++ b/cgroup.c
@@ -951,6 +951,12 @@ void fini_cgroup(void)
        cg_yard = NULL;
 }

+void umount_cgyard(void)
+{
+       if (cg_yard)
+               umount2(cg_yard, MNT_DETACH);
+}
+
 static int restore_cgroup_prop(const CgroupPropEntry * cg_prop_entry_p,
                               char *path, int off)
 {
diff --git a/include/cgroup.h b/include/cgroup.h
index 14fef67..5bcf028 100644
--- a/include/cgroup.h
+++ b/include/cgroup.h
@@ -10,6 +10,7 @@ int prepare_cgroup(void);
 /* Restore things like cpu_limit in known cgroups. */
 int prepare_cgroup_properties(void);
 void fini_cgroup(void);
+void umount_cgyard(void);

 struct cg_controller;

diff --git a/mount.c b/mount.c
index e59cb0d..b0b34cb 100644
--- a/mount.c
+++ b/mount.c
@@ -2028,6 +2028,7 @@ int restore_task_mnt_ns(struct pstree_item *current)

                if (do_restore_task_mnt_ns(nsid))
                        return -1;
+               umount_cgyard();
        }

        return 0;
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