typedef struct _PRIVATE_CACHE_MAP
{
     union
     {
          SHORT NodeTypeCode;
          PRIVATE_CACHE_MAP_FLAGS Flags;
          ULONG UlongFlags;
     };
     ULONG ReadAheadMask;
     PFILE_OBJECT FileObject;
     LARGE_INTEGER FileOffset1;
     LARGE_INTEGER BeyondLastByte1;
     LARGE_INTEGER FileOffset2;
     LARGE_INTEGER BeyondLastByte2;
     LARGE_INTEGER ReadAheadOffset[2];
     ULONG ReadAheadLength[2];
     ULONG ReadAheadSpinLock;
     LIST_ENTRY PrivateLinks;
} PRIVATE_CACHE_MAP, *PPRIVATE_CACHE_MAP;

Windows Vista Kernel Structures