[PATCH v4 0/4] mm: userfaultfd: refactor and add UFFDIO_CONTINUE_MODE_WP

[Axel Rasmussen]

This series, currently based on 6.3-rc1, is divided into two parts:

- Commits 1-3 refactor userfaultfd ioctl code without behavior changes, with the
  main goal of improving consistency and reducing the number of function args.
- Commit 4 adds UFFDIO_CONTINUE_MODE_WP.

The refactors are sorted by increasing controversial-ness, the idea being we
could drop some of the refactors if they are deemed not worth it.

Changelog:

v3->v4:
 - massage the uffd_flags_t implementation to eliminate all sparse warnings
 - add a couple inline helpers to make uffd_flags_t usage easier
 - drop the refactor passing `struct uffdio_range *` around (previously 4/5)
 - define a temporary `struct mm_struct *` in function with >=3 `vma->vm_mm`
 - consistent argument order between `flags` and `pagep`
 - expand on the use case in patch 4/4 message

v2->v3:
 - rebase onto 6.3-rc1
 - typedef a new type for mfill flags in patch 3/5 (suggested by Nadav)

v1->v2:
 - refactor before adding the new flag, to avoid perpetuating messiness

Axel Rasmussen (4):
  mm: userfaultfd: rename functions for clarity + consistency
  mm: userfaultfd: don't pass around both mm and vma
  mm: userfaultfd: combine 'mode' and 'wp_copy' arguments
  mm: userfaultfd: add UFFDIO_CONTINUE_MODE_WP to install WP PTEs

 fs/userfaultfd.c                         |  29 ++--
 include/linux/hugetlb.h                  |  27 ++--
 include/linux/shmem_fs.h                 |   9 +-
 include/linux/userfaultfd_k.h            |  68 +++++----
 include/uapi/linux/userfaultfd.h         |   7 +
 mm/hugetlb.c                             |  28 ++--
 mm/shmem.c                               |  14 +-
 mm/userfaultfd.c                         | 170 +++++++++++------------
 tools/testing/selftests/mm/userfaultfd.c |   4 +
 9 files changed, 187 insertions(+), 169 deletions(-)

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2.40.0.rc1.284.g88254d51c5-goog