linux-kernel - [RFC PATCH 0/3] Add hugetlb MADV

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Message-Id: <20220113180308.15610-1-mike.kravetz@oracle.com>
Date:   Thu, 13 Jan 2022 10:03:05 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Michal Hocko <mhocko@...e.com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [RFC PATCH 0/3] Add hugetlb MADV_DONTNEED support

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.

hugetlb does not support MADV_DONTNEED.  However, the only thing
preventing support is a check in can_madv_lru_vma().  Simply removing
the check will enable support.

This is sent as a RFC because there is no existing use case calling
for hugetlb MADV_DONTNEED support except possibly the userfaultfd test.
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.

Once support is added, the madvise man page will need to be updated.

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                                 |   9 +-
 tools/testing/selftests/vm/Makefile          |   1 +
 tools/testing/selftests/vm/hugetlb-madvise.c | 315 +++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests.sh    |  12 +
 tools/testing/selftests/vm/userfaultfd.c     |  67 ++--
 5 files changed, 369 insertions(+), 35 deletions(-)
 create mode 100644 tools/testing/selftests/vm/hugetlb-madvise.c

-- 
2.34.1