That's exactly what we agreed on during our discussions:
When page is get touched it is charged to this container.
When page is get touched again by new container it is NOT
charged to new container, but keeps holding the old one
till it (the page) is completely freed. Nobody worried the
fact that a single page can hold container for good.
OpenVZ beancounters work the other way (and we proposed this
solution when we first sent the patches). We keep track of
*all* the containers (i.e. beancounters) holding this page.
We can migrate page to another user but we decided
to implement it later after accepting simple accounting.