MM: Support more pagesizes for MAP_HUGETLB/SHM_HUGETLB v7 fix fix fix

MM: Support more pagesizes for MAP_HUGETLB/SHM_HUGETLB v7 fix fix fix

On Fri, 9 Nov 2012, Randy Dunlap wrote:

> on x86_64:
>
> In file included from mm/mprotect.c:13:0:
> include/linux/shm.h:57:20: error: redefinition of 'do_shmat'
> include/linux/shm.h:57:20: note: previous definition of 'do_shmat' was here
> include/linux/shm.h:63:19: error: redefinition of 'is_file_shm_hugepages'
> include/linux/shm.h:63:19: note: previous definition of 'is_file_shm_hugepages' was here
> include/linux/shm.h:67:20: error: redefinition of 'exit_shm'
> include/linux/shm.h:67:20: note: previous definition of 'exit_shm' was here
>
> In file included from include/linux/hugetlb.h:16:0,
>                  from mm/mmap.c:23:
> include/linux/shm.h:57:20: error: redefinition of 'do_shmat'
> include/linux/shm.h:57:20: note: previous definition of 'do_shmat' was here
> include/linux/shm.h:63:19: error: redefinition of 'is_file_shm_hugepages'
> include/linux/shm.h:63:19: note: previous definition of 'is_file_shm_hugepages' was here
> include/linux/shm.h:67:20: error: redefinition of 'exit_shm'
> include/linux/shm.h:67:20: note: previous definition of 'exit_shm' was here
> make[2]: *** [mm/mprotect.o] Error 1
>

This is an elusive one, I couldn't reproduce it with master.  This appears
to only happen on the akpm branch, correct?

It happens because of e37c64a9751a ("mm: support more pagesizes for
MAP_HUGETLB/SHM_HUGETLB") adds a spurious "#endif" to include/linux/shm.h
and gets reverted in master by 359078d82a20 ("Revert "mm: support more
pagesizes for MAP_HUGETLB/SHM_HUGETLB"") because of another build failure
that Stephen reports on November 8:

mm/mmap.c: In function 'SYSC_mmap_pgoff':
mm/mmap.c:1271:15: error: 'MAP_HUGE_SHIFT' undeclared (first use in this function)
mm/mmap.c:1271:15: note: each undeclared identifier is reported only once for each function it appears in
mm/mmap.c:1271:33: error: 'MAP_HUGE_MASK' undeclared (first use in this function)

I think the best bet would be to merge the following in -mm and then let
Stephen revert it in master again if his build error persists for powerpc:

mm-support-more-pagesizes-for-map_hugetlb-shm_hugetlb-v7-fix-fix-fix

Fix the build:

include/linux/shm.h:57:20: error: redefinition of 'do_shmat'
include/linux/shm.h:57:20: note: previous definition of 'do_shmat' was here
include/linux/shm.h:63:19: error: redefinition of 'is_file_shm_hugepages'
include/linux/shm.h:63:19: note: previous definition of 'is_file_shm_hugepages' was here
include/linux/shm.h:67:20: error: redefinition of 'exit_shm'
include/linux/shm.h:67:20: note: previous definition of 'exit_shm' was here

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>