[PATCH v6 00/12] mm: establish const-correctness for pointer parameters

[Max Kellermann <max.kellermann@ionos.com>]

For improved const-correctness in the low-level memory-management
subsystem, which provides a basis for further const-ification further
up the call stack (e.g. filesystems).

This patch series splitted into smaller patches was initially posted
as a single large patch:

 https://lore.kernel.org/lkml/20250827192233.447920-1-max.kellermann@ionos.com/

I started this work when I tried to constify the Ceph filesystem code,
but found that to be impossible because many "mm" functions accept
non-const pointer, even though they modify nothing.

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
v1 -> v2:
- made several parameter values const (i.e. the pointer address, not
  just the pointed-to memory), as suggested by Andrew Morton and
  Yuanchu Xie
- drop existing+obsolete "extern" keywords on lines modified by these
  patches (suggested by Vishal Moola)
- add missing parameter names on lines modified by these patches
  (suggested by Vishal Moola)
- more "const" pointers (e.g. the task_struct passed to
  process_shares_mm())
- add missing "const" to s390, fixing s390 build failure
- moved the mmap_is_legacy() change in arch/s390/mm/mmap.c from 08/12
  to 06/12 (suggested by Vishal Moola)

v2 -> v3:
- remove garbage from 06/12
- changed tags on subject line (suggested by Matthew Wilcox)

v3 -> v4:
- more verbose commit messages including a listing of function names
  (suggested by David Hildenbrand and Lorenzo Stoakes)

v4 -> v5:
- back to shorter commit messages after an agreement between David
  Hildenbrand and Lorenzo Stoakes was found

v5 -> v6:
- fix inconsistent constness of assert_fault_locked()
- revert the const parameter value change from v2 (requested by
  Lorenzo Stoakes)
- revert the long cover letter, removing long explanations again
  (requested by Lorenzo Stoakes)

Max Kellermann (12):
  mm: constify shmem related test functions for improved
    const-correctness
  mm: constify pagemap related test/getter functions
  mm: constify zone related test/getter functions
  fs: constify mapping related test functions for improved
    const-correctness
  mm: constify process_shares_mm() for improved const-correctness
  mm, s390: constify mapping related test/getter functions
  parisc: constify mmap_upper_limit() parameter
  mm: constify arch_pick_mmap_layout() for improved const-correctness
  mm: constify ptdesc_pmd_pts_count() and folio_get_private()
  mm: constify various inline functions for improved const-correctness
  mm: constify assert/test functions in mm.h
  mm: constify highmem related functions for improved const-correctness

 arch/arm/include/asm/highmem.h      |  6 +--
 arch/parisc/include/asm/processor.h |  2 +-
 arch/parisc/kernel/sys_parisc.c     |  2 +-
 arch/s390/mm/mmap.c                 |  6 +--
 arch/sparc/kernel/sys_sparc_64.c    |  2 +-
 arch/x86/mm/mmap.c                  |  6 +--
 arch/xtensa/include/asm/highmem.h   |  2 +-
 include/linux/fs.h                  |  6 +--
 include/linux/highmem-internal.h    | 36 +++++++++---------
 include/linux/highmem.h             |  8 ++--
 include/linux/mm.h                  | 56 +++++++++++++--------------
 include/linux/mm_inline.h           | 25 ++++++------
 include/linux/mm_types.h            |  4 +-
 include/linux/mmzone.h              | 42 ++++++++++----------
 include/linux/pagemap.h             | 59 +++++++++++++++--------------
 include/linux/sched/mm.h            |  4 +-
 include/linux/shmem_fs.h            |  4 +-
 mm/highmem.c                        | 10 ++---
 mm/oom_kill.c                       |  6 +--
 mm/shmem.c                          |  6 +--
 mm/util.c                           | 16 ++++----
 21 files changed, 155 insertions(+), 153 deletions(-)

-- 
2.47.2