Please, add a possibility to libvirt to specify a diskspace and diskinodes tags for openvz based domains. There is a thread in mail archive available at http://www.mail-archive.com/libvir-list@redhat.com/msg07329.html where these feature was described.
I think this is upstream: commit e63845469e51d95e2628218a27432d26d5787f2a Author: Guido Günther <agx> Date: Sat May 5 08:52:23 2012 +0200 openvz: add quota argument when creating container