[0/3] Add hugetlb MADV_DONTNEED support

Message

Mike Kravetz Jan. 28, 2022, 10:26 p.m. UTC

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.

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

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/Makefile          |   1 +
 tools/testing/selftests/vm/hugetlb-madvise.c | 401 +++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests.sh    |  12 +
 tools/testing/selftests/vm/userfaultfd.c     |  67 ++--
 5 files changed, 470 insertions(+), 35 deletions(-)
 create mode 100644 tools/testing/selftests/vm/hugetlb-madvise.c