[v3,0/3] mm/hugetlb: Fix selftest failures with write check

Message

Peter Xu Oct. 4, 2022, 7:33 p.m. UTC

v3:
- Rebase to akpm mm-unstable
v2:
- Fix the commit message of patch 1, replacing CoW with wr-unprotect
  example

Currently akpm mm-unstable fails with uffd hugetlb private mapping test
randomly on a write check.

The initial bisection of that points to the recent pmd unshare series, but
it turns out there's no direction relationship with the series but only
some timing change caused the race to start trigger.

The race should be fixed in patch 1.  Patch 2 is a trivial cleanup on the
similar race with hugetlb migrations, patch 3 comment on the write check
so when anyone read it again it'll be clear why it's there.

Thanks,

Peter Xu (3):
  mm/hugetlb: Fix race condition of uffd missing/minor handling
  mm/hugetlb: Use hugetlb_pte_stable in migration race check
  mm/selftest: uffd: Explain the write missing fault check

 mm/hugetlb.c                             | 66 ++++++++++++++++++++----
 tools/testing/selftests/vm/userfaultfd.c | 22 +++++++-
 2 files changed, 76 insertions(+), 12 deletions(-)