newly add MAP_SYNC flag to mmap

[David Frank]

 Thanks Valdis.
Yes, I got the kernel and header files installed.
But there seems to be a lot of mman.h. I found one in /usr/include/asm-generic that defined MAP_SYNC, and I included it also, now I got passed compile and linking. I'm checking out if the flag does what is is said to do-- I don't have to call msync function, which would boost performance.

    On Monday, July 16, 2018, 10:04:54 PM EDT, <valdis.kletnieks at vt.edu> wrote:  
 
 On Tue, 17 Jul 2018 00:57:31 -0000, David Frank said:

> I installed LTS 18.04 with headers.  I'm trying to use the new flag MAP_SYNC
> with mmap call, but it complained MAP_SYNC undefined.What #define do I need to
> enable this?

You need more than a #define. You need a 4.15 kernel and matching
kernel-headers. But if you installed 18.04 correctly, those should be in place
already, as that apparently shipped with 4.15...

Or if you're not really a kernel person, but a misplaced userspace person,
'man 2 mmap' tells us:

NAME
      mmap, munmap - map or unmap files or devices into memory

SYNOPSIS
      #include <sys/mman.h>_______________________________________________
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