[CRIU] Preserve the "dumpable" flag on criu dump/restore.

[Filipe Brandenburger]

Hi,

Sorry for the double report, but I didn't know whether Bugzilla or
mailing list was more appropriate...

I found this issue with the files in /proc/$pid being owned by
root:root after a criu restore. I traced it to the fact that the
"dumpable" flag for the task does not get preserved over a criu
dump/restore.

I filed this bug about it:
https://bugzilla.openvz.org/show_bug.cgi?id=2968

And I sent this patch which fixes the issue:
http://2968.bugzilla.openvz.org/attachment.cgi?id=2147

While testing the patch with zdtm, I also found that it caused
static/cow01 to break. After some investigation, I got to the
conclusion that cow01 was inherently broken and without the "dumpable"
flag being preserved it would always succeed even though it was not
really checking whether pages are COWed...

On the other hand, after the fix to preserve the "dumpable" flag, then
test static/cow01 was failing consistently. It turns out that it seems
that COW is not really working as expected, and now that the test was
fixed it's showing that this is actually broken.

I filed this bug to report the fact that the static/cow01 test seems
to be broken:
https://bugzilla.openvz.org/show_bug.cgi?id=2967

It seems that COW support itself also needs to be fixed. I'm currently
looking into it but I'm not really sure where the problem is yet.

Let me know if you have any questions about the dumpable flag patch.

Thanks!
Filipe