Many of the member fields in filemap.hpp are declared with public accessibility. This is contrary to HotSpot coding style, and also makes the code unnecessarily intertwined.

http://hg.openjdk.java.net/jdk/jdk/file/bf3fb5465543/src/hotspot/share/memory/filemap.hpp#l128

We should make the fields private and add accessor functions where necessary.

Also, FileMapInfo::_header should not be accessed directly from other code. We should provide accessor functions similar to FileMapInfo::core_spaces_size() to access information stored in the header.