xemul: There's bfd over pagemap images:

mike: Yes, but the bfd caches raw protobuf data, while the in-memory pagemap
      caches unpacked PagemapEntrie's. There's indeed some duplication, but
      you anyway have to go through 'bread -> unpack' to use pagemap.

      Also we read the entire pagemap and then close the image thus freeing
      the bfd cache.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>