mmap huge page and MAP_SYNC flag support

Hi,How do I enable the MAP_SYNC flag in mmap for linux 4.15, my code does not compile with that flag on linux 4.15.0-041500rc7-generic #201801072330 Also, how do I make mmap support map size of 2GB or larger, currently the call to mmap fails with mapsize of 2GB. thanks, David