[PATCH v7 0/4] Fix free/allocation of runtime gigantic pages

[Alexandre Ghiti <alex@ghiti.fr>]

his series fixes sh and sparc that did not advertise their gigantic page
support and then were not able to allocate and free those pages at runtime.
It renames MEMORY_ISOLATION && COMPACTION || CMA condition into the more
accurate CONTIG_ALLOC, since it allows the definition of alloc_contig_range
function.
Finally, it then fixes the wrong definition of ARCH_HAS_GIGANTIC_PAGE config
that, without MEMORY_ISOLATION && COMPACTION || CMA defined, did not allow
architectures to free boottime allocated gigantic pages although unrelated.

Changes in v7:
  I thought gigantic page support was settled at compile time, but Aneesh
  and Michael have just come up with a patch proving me wrong for
  powerpc: https://patchwork.ozlabs.org/patch/1047003/. So this version:
  - reintroduces gigantic_page_supported renamed into
    gigantic_page_runtime_supported
  - reintroduces gigantic page page support corresponding checks (not
    everywhere though: set_max_huge_pages check was redundant with
    __nr_hugepages_store_common)
  - introduces the possibility for arch to override this function
    by using asm-generic/hugetlb.h current semantics although Aneesh
    proposed something else.

Changes in v6:
- Remove unnecessary goto since the fallthrough path does the same and is
  the 'normal' behaviour, as suggested by Dave Hensen
- Be more explicit in comment in set_max_huge_page: we return an error
  if alloc_contig_range is not defined and the user tries to allocate a
  gigantic page (we keep the same behaviour as before this patch), but we
  now let her free boottime gigantic page, as suggested by Dave Hensen
- Add Acked-by, thanks. 

Changes in v5:
- Fix bug in previous version thanks to Mike Kravetz
- Fix block comments that did not respect coding style thanks to Dave Hensen
- Define ARCH_HAS_GIGANTIC_PAGE only for sparc64 as advised by David Miller
- Factorize "def_bool" and "depends on" thanks to Vlastimil Babka

Changes in v4 as suggested by Dave Hensen:
- Split previous version into small patches
- Do not compile alloc_gigantic** functions for architectures that do not
  support those pages
- Define correct ARCH_HAS_GIGANTIC_PAGE in all arch that support them to avoid
  useless runtime check
- Add comment in set_max_huge_pages to explain that freeing is possible even
  without CONTIG_ALLOC defined
- Remove gigantic_page_supported function across all archs

Changes in v3 as suggested by Vlastimil Babka and Dave Hansen:
- config definition was wrong and is now in mm/Kconfig
- COMPACTION_CORE was renamed in CONTIG_ALLOC

Changes in v2 as suggested by Vlastimil Babka:
- Get rid of ARCH_HAS_GIGANTIC_PAGE
- Get rid of architecture specific gigantic_page_supported
- Factorize CMA or (MEMORY_ISOLATION && COMPACTION) into COMPACTION_CORE 

Alexandre Ghiti (4):
  sh: Advertise gigantic page support
  sparc: Advertise gigantic page support
  mm: Simplify MEMORY_ISOLATION && COMPACTION || CMA into CONTIG_ALLOC
  hugetlb: allow to free gigantic pages regardless of the configuration

 arch/arm64/Kconfig                           |  2 +-
 arch/arm64/include/asm/hugetlb.h             |  4 --
 arch/powerpc/include/asm/book3s/64/hugetlb.h |  7 ---
 arch/powerpc/platforms/Kconfig.cputype       |  2 +-
 arch/s390/Kconfig                            |  2 +-
 arch/s390/include/asm/hugetlb.h              |  3 --
 arch/sh/Kconfig                              |  1 +
 arch/sparc/Kconfig                           |  1 +
 arch/x86/Kconfig                             |  2 +-
 arch/x86/include/asm/hugetlb.h               |  4 --
 arch/x86/mm/hugetlbpage.c                    |  2 +-
 include/asm-generic/hugetlb.h                | 14 +++++
 include/linux/gfp.h                          |  4 +-
 mm/Kconfig                                   |  3 ++
 mm/hugetlb.c                                 | 54 ++++++++++++++------
 mm/page_alloc.c                              |  7 ++-
 16 files changed, 67 insertions(+), 45 deletions(-)

-- 
2.20.1