[PATCH v2 0/3] Add hugetlb MADV_DONTNEED support

From: Mike Kravetz <mike.kravetz@oracle.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>,
	David Hildenbrand <david@redhat.com>,
	Axel Rasmussen <axelrasmussen@google.com>,
	Mina Almasry <almasrymina@google.com>,
	Michal Hocko <mhocko@suse.com>, Peter Xu <peterx@redhat.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Shuah Khan <shuah@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: [PATCH v2 0/3] Add hugetlb MADV_DONTNEED support
Date: Tue,  1 Feb 2022 17:40:31 -0800	[thread overview]
Message-ID: <20220202014034.182008-1-mike.kravetz@oracle.com> (raw)

Userfaultfd selftests for hugetlb does not perform UFFD_EVENT_REMAP
testing.  However, mremap support was recently added in commit
550a7d60bd5e ("mm, hugepages: add mremap() support for hugepage backed
vma").  While attempting to enable mremap support in the test, it was
discovered that the mremap test indirectly depends on MADV_DONTNEED.

madvise does not allow MADV_DONTNEED for hugetlb mappings.  However,
that is primarily due to the check in can_madv_lru_vma().  By simply
removing the check and adding huge page alignment, MADV_DONTNEED can
be made to work for hugetlb mappings.

Do note that there is no compelling use case for adding this support.
This was discussed in the RFC [1].  However, adding support makes sense
as it is fairly trivial and brings hugetlb functionality more in line
with 'normal' memory.

After enabling support, add selftest for MADV_DONTNEED as well as
MADV_REMOVE.  Then update userfaultfd selftest.

v1 -> v2
- Use is_vm_hugetlb_page() instead of open coding vma hugetlb check.
- Add new test to .gitignore and use meaningful symbolic names (#define)
  for constants used in test.  Shuah
- Updated help text in userfaultfd test and modified run_vmtests to not
  pass in a file for userfaultfd hugetlb test.  Axel
- Added Reviewed-by for selftest patches.

RFC -> v1
- Fixed alignment issues when calling zap_page_range.  Naoya
- Added checks for invalid arguments and misalignment to selftest.

[1] https://lore.kernel.org/linux-mm/20220113180308.15610-1-mike.kravetz@oracle.com/

Mike Kravetz (3):
  mm: enable MADV_DONTNEED for hugetlb mappings
  selftests/vm: add hugetlb madvise MADV_DONTNEED MADV_REMOVE test
  userfaultfd/selftests: enable huegtlb remap and remove event testing

 mm/madvise.c                                 |  24 +-
 tools/testing/selftests/vm/.gitignore        |   1 +
 tools/testing/selftests/vm/Makefile          |   1 +
 tools/testing/selftests/vm/hugetlb-madvise.c | 413 +++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests.sh    |  15 +-
 tools/testing/selftests/vm/userfaultfd.c     |  69 ++--
 6 files changed, 485 insertions(+), 38 deletions(-)
 create mode 100644 tools/testing/selftests/vm/hugetlb-madvise.c

-- 
2.34.1