linux-kernel - [PATCH v5 0/4] mm: userfaultfd: refactor and add UFFDIO_CONTINUE_MODE

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Date:   Tue, 14 Mar 2023 15:12:46 -0700
From:   Axel Rasmussen <axelrasmussen@...gle.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>, Jan Kara <jack@...e.cz>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>,
        Nadav Amit <namit@...are.com>, Peter Xu <peterx@...hat.com>,
        Shuah Khan <shuah@...nel.org>
Cc:     James Houghton <jthoughton@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        Axel Rasmussen <axelrasmussen@...gle.com>
Subject: [PATCH v5 0/4] mm: userfaultfd: refactor and add UFFDIO_CONTINUE_MODE_WP

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:

v4->v5:
 - rename "uffd_flags_has_mode" to "uffd_flags_mode_is"
 - modify "uffd_flags_set_mode" to clear mode bits before setting new mode
 - update userfaultfd documentation to describe new mode flag

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

 Documentation/admin-guide/mm/userfaultfd.rst |   8 +
 fs/userfaultfd.c                             |  29 ++--
 include/linux/hugetlb.h                      |  27 ++-
 include/linux/shmem_fs.h                     |   9 +-
 include/linux/userfaultfd_k.h                |  69 +++++---
 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 +
 10 files changed, 196 insertions(+), 169 deletions(-)

--
2.40.0.rc1.284.g88254d51c5-goog