x86/mm: Fix more ballooning+paging and ballooning+sharing bugs
If the guest balloons away a page that has been nominated for paging but
not yet paged out, we fix:
- Send EVICT_FAIL flag in the event to the pager
- Do not leak the underlying page
If the page was shared, we were not:
- properly refreshing the mfn to balloon after the unshare.
- unlocking the p2m on the error exit case
Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>