[PATCH 0/6] mm/uffd: Misc fix for uffd-wp and one more test

[Peter Xu <peterx@redhat.com>]

This series is based on (mostly) v5.12-rc8-mmots-2021-04-21-23-08.  It tries to
fix some corner case bugs for uffd-wp on either thp or fork().  Then it
introduced a new test with pagemap/pageout.

Patch layout:

Patch 1:    cleanup for THP, it'll slightly simplify the follow up patches
Patch 2-4:  misc fixes for uffd-wp here and there; please refer to each patch
Patch 5:    add pagemap support for uffd-wp
Patch 6:    add pagemap/pageout test for uffd-wp

The last test introduced can also verify some of the fixes in previous patches,
as the test will fail without the fixes.  However it's not easy to verify all
the changes in patch 2-4, but hopefully they can still be properly reviewed.

Note that if considering the ongoing uffd-wp shmem & hugetlbfs work, patch 5
will be incomplete as it's missing e.g. hugetlbfs part or the special swap pte
detection.  However that's not needed in this series, and since that series is
still during review, this series does not depend on that one (the last test
only runs with anonymous memory, not file-backed).  So this series can be
merged even before that series.

Please review, thanks.

Peter Xu (6):
  mm/thp: Simplify copying of huge zero page pmd when fork
  mm/userfaultfd: Fix uffd-wp special cases for fork()
  mm/userfaultfd: Fix a few thp pmd missing uffd-wp bit
  mm/userfaultfd: Fail uffd-wp registeration if not supported
  mm/pagemap: Export uffd-wp protection information
  userfaultfd/selftests: Add pagemap uffd-wp test

 Documentation/admin-guide/mm/pagemap.rst |   2 +
 fs/proc/task_mmu.c                       |   9 ++
 fs/userfaultfd.c                         |   9 +-
 include/linux/huge_mm.h                  |   2 +-
 include/linux/swapops.h                  |   2 +
 mm/huge_memory.c                         |  36 +++---
 mm/memory.c                              |  25 ++--
 tools/testing/selftests/vm/userfaultfd.c | 154 +++++++++++++++++++++++
 8 files changed, 206 insertions(+), 33 deletions(-)

-- 
2.26.2