linux-kernel - [PATCH v3 00/12] mm: add `const` to lots of pointer parameters

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Message-ID: <20250901061223.2939097-1-max.kellermann@ionos.com>
Date: Mon,  1 Sep 2025 08:12:11 +0200
From: Max Kellermann <max.kellermann@...os.com>
To: akpm@...ux-foundation.org,
	david@...hat.com,
	axelrasmussen@...gle.com,
	yuanchu@...gle.com,
	willy@...radead.org,
	hughd@...gle.com,
	mhocko@...e.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	vbabka@...e.cz,
	rppt@...nel.org,
	surenb@...gle.com,
	vishal.moola@...il.com
Cc: Max Kellermann <max.kellermann@...os.com>
Subject: [PATCH v3 00/12] mm: add `const` to lots of pointer parameters

For improved const-correctness.

This work was initially posted here:
 https://lore.kernel.org/lkml/20250827192233.447920-1-max.kellermann@ionos.com/

.. but got rejected by Lorenzo Stoakes:
 https://lore.kernel.org/lkml/d6bf808d-7d74-4e22-ac4b-a6d1f4892262@lucifer.local/

David Hildenbrand and Lorenzo Stoakes suggested splitting the patch
into smaller chunks.  My second attempt with one smaller patch was met
with agreement:

 https://lore.kernel.org/lkml/20250828130311.772993-1-max.kellermann@ionos.com/

Now this is the rest of the initial patch in small pieces, plus some
more.

Establishing const-correctness in this low-level part of the kernel
enables doing the same in higher-level parts, e.g. filesystems.

Signed-off-by: Max Kellermann <max.kellermann@...os.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)

Max Kellermann (12):
  mm/shmem: add `const` to lots of pointer parameters
  mm/pagemap: add `const` to lots of pointer parameters
  mm/mmzone: add `const` to lots of pointer parameters
  fs: add `const` to several pointer parameters
  mm/oom_kill: add `const` to pointer parameter
  mm/util, s390: add `const` to several pointer parameters
  parisc: add `const` to mmap_upper_limit() parameter
  mm/util, s390, sparc, x86: add const to arch_pick_mmap_layout()
    parameter
  mm/mm_types: add `const` to several pointer parameters
  mm/mm_inline: add `const` to lots of pointer parameters
  mm: add `const` to lots of pointer parameters
  mm/highmem: add `const` to lots of pointer parameters

 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                 |  7 ++--
 arch/sparc/kernel/sys_sparc_64.c    |  3 +-
 arch/x86/mm/mmap.c                  |  7 ++--
 arch/xtensa/include/asm/highmem.h   |  2 +-
 include/linux/fs.h                  |  7 ++--
 include/linux/highmem-internal.h    | 38 ++++++++++---------
 include/linux/highmem.h             |  8 ++--
 include/linux/mm.h                  | 48 +++++++++++------------
 include/linux/mm_inline.h           | 26 +++++++------
 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                       |  3 +-
 mm/shmem.c                          |  6 +--
 mm/util.c                           | 20 ++++++----
 21 files changed, 162 insertions(+), 146 deletions(-)

-- 
2.47.2