Unify hugetlb into arch_get_unmapped_area functions [LWN.net]

From:		Oscar Salvador <osalvador-AT-suse.de>
To:		Andrew Morton <akpm-AT-linux-foundation.org>
Subject:		[RFC PATCH 0/8] Unify hugetlb into arch_get_unmapped_area functions
Date:		Wed, 10 Jul 2024 12:50:34 +0200
Message-ID:		<20240710105042.30165-1-osalvador@suse.de>
Cc:		linux-kernel-AT-vger.kernel.org, linux-mm-AT-kvack.org, Muchun Song <muchun.song-AT-linux.dev>, David Hildenbrand <david-AT-redhat.com>, Michal Hocko <mhocko-AT-suse.com>, Donet Tom <donettom-AT-linux.ibm.com>, "Kirill A . Shutemov" <kirill.shutemov-AT-linux.intel.com>, Matthew Wilcox <willy-AT-infradead.org>, Vlastimil Babka <vbabka-AT-suse.cz>, Oscar Salvador <osalvador-AT-suse.de>
Archive-link:		Article

Hi all,

this is a first attempt to get rid of a fair amount of duplicated code
wrt. hugetlb and *get_unmapped_area* functions.

HugeTLB registers a .get_unmapped_area function which gets called from
__get_unmapped_area().
hugetlb_get_unmapped_area() is defined by a bunch of architectures and
it also has a generic definition for those that do not define it.
Short-long story is that there is a ton of duplicated code between
specific hugetlb *_get_unmapped_area_* functions and mm-core functions,
so we can do better by teaching arch_get_unmapped_area* functions how
to deal with hugetlb mappings.

Note that not a lot of things need to be taught though.
hugetlb_mmap_check_and_align(), that gets called for hugetlb mappings
prior to call mm_get_unmapped_area_vmflags(), runs some sanity checks
and aligns the addr to huge_page_size(), so we do not need to that
down the road in the respective {generic,arch}_get_unmapped_area*
functions.

More information can be found in the respective patches.

LTP mmapstress and hugemmap testcases were ran on arm64, powerpc64le and
x86_64 without raising any issue.

Oscar Salvador (8):
  mm/mmap: Teach generic_get_unmapped_area{_topdown} to handle hugetlb
    mappings
  arch/s390: Teach arch_get_unmapped_area{_topdown} to handle hugetlb
    mappings
  arch/x86: Teach arch_get_unmapped_area_vmflags to handle hugetlb
    mappings
  arch/sparc: Teach arch_get_unmapped_area{_topdown} to handle hugetlb
    mappings
  arch/powerpc: Teach book3s64 arch_get_unmapped_area{_topdown} to
    handle hugetlb mappings
  mm: Make hugetlb mappings go through mm_get_unmapped_area_vmflags
  mm: Drop hugetlb_get_unmapped_area{_*} functions
  mm: Consolidate common checks in hugetlb_mmap_check_and_align

 arch/loongarch/include/asm/hugetlb.h |   4 -
 arch/mips/include/asm/hugetlb.h      |   4 -
 arch/parisc/include/asm/hugetlb.h    |  15 ----
 arch/parisc/mm/hugetlbpage.c         |  23 ------
 arch/powerpc/mm/book3s64/slice.c     |  49 +++++++-----
 arch/s390/include/asm/hugetlb.h      |  16 ----
 arch/s390/mm/hugetlbpage.c           |  84 ---------------------
 arch/s390/mm/mmap.c                  |   8 +-
 arch/sh/include/asm/hugetlb.h        |  15 ----
 arch/sparc/kernel/sys_sparc_32.c     |  16 +++-
 arch/sparc/kernel/sys_sparc_64.c     |  36 +++++++--
 arch/sparc/mm/hugetlbpage.c          | 108 ---------------------------
 arch/x86/kernel/sys_x86_64.c         |  24 ++++--
 arch/x86/mm/hugetlbpage.c            | 100 -------------------------
 fs/hugetlbfs/inode.c                 |  92 ++---------------------
 include/asm-generic/hugetlb.h        |   7 --
 include/linux/hugetlb.h              |  21 +++---
 mm/mmap.c                            |  19 ++++-
 18 files changed, 129 insertions(+), 512 deletions(-)

-- 
2.45.2