shmem: dump anon shared memory pages according to their PME derived states
shmem: dump anon shared memory pages according to their PME derived states

This allows us not to dump anon shmem pages that weren't changed since
last dump. We dump each anon shmem vma using page-xfer. page-xfer does all
magic with storing "in_parent" field in pagemap-entry.
When restoring we simply read every page with page-read and it does
all magic of reading from right place in image hierarchy.
auto-dedup on restore is already implemented by page-read so we don't need
to code it.

Signed-off-by: Fyodor Bocharov <a27cde000565307013cc2099fc7a062271855638@yandex.ru>
Signed-off-by: Eugene Batalov <7a4372f440491fdba11e6e9c63b691b267a65e67@gmail.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@virtuozzo.com>

eabatalov/criu,eabatalov/criu,eabatalov/criu,eabatalov/criu,eabatalov/criu,eabatalov/criu