POSIX_FADV_NORMAL	0
POSIX_FADV_RANDOM	1
POSIX_FADV_SEQUENTIAL	2
POSIX_FADV_WILLNEED	3
#if defined __s390x__
POSIX_FADV_DONTNEED	6
POSIX_FADV_NOREUSE	7
#else
POSIX_FADV_DONTNEED	4
POSIX_FADV_NOREUSE	5
#endif