mm: hugetlb: define system call hugetlb size encodings in single file

mm: hugetlb: define system call hugetlb size encodings in single file

Patch series "Consolidate system call hugetlb page size encodings".

These patches are the result of discussions in
https://lkml.org/lkml/2017/3/8/548.  The following changes are made in the
patch set:

1) Put all the log2 encoded huge page size definitions in a common
   header file.  The idea is have a set of definitions that can be use as
   the basis for system call specific definitions such as MAP_HUGE_* and
   SHM_HUGE_*.

2) Remove MAP_HUGE_* definitions in arch specific files.  All these
   definitions are the same.  Consolidate all definitions in the primary
   user header file (uapi/linux/mman.h).

3) Remove SHM_HUGE_* definitions intended for user space from kernel
   header file, and add to user (uapi/linux/shm.h) header file.  Add
   definitions for all known huge page size encodings as in mmap.

This patch (of 3):

If hugetlb pages are requested in mmap or shmget system calls, a huge
page size other than default can be requested.  This is accomplished by
encoding the log2 of the huge page size in the upper bits of the flag
argument.  asm-generic and arch specific headers all define the same
values for these encodings.

Put common definitions in a single header file.  The primary uapi header
files for mmap and shm will use these definitions as a basis for
definitions specific to those system calls.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Kravetz <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>