With in-memory pagemap put_pagemap is not required because it does not
frees any resources. Minor modifications to get_pagemap and init_pagemaps
allow proper bookkeeping without put_pagemap.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>