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@xxxxxxxxxx/
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
