+ mm-constify-shmem-related-test-functions-for-improved-const-correctness.patch added to mm-new branch

+ mm-constify-shmem-related-test-functions-for-improved-const-correctness.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm: constify shmem related test functions for improved const-correctness
has been added to the -mm mm-new branch.  Its filename is
     mm-constify-shmem-related-test-functions-for-improved-const-correctness.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-constify-shmem-related-test-functions-for-improved-const-correctness.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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------------------------------------------------------
From: Max Kellermann <max.kellermann@ionos.com>
Subject: mm: constify shmem related test functions for improved const-correctness
Date: Mon, 1 Sep 2025 22:50:10 +0200

Patch series "mm: establish const-correctness for pointer parameters", v6.

This series is to improved const-correctness in the low-level
memory-management subsystem, which provides a basis for further
constification further up the call stack (e.g.  filesystems).

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
pointers, even though they modify nothing.


This patch (of 12):

We select certain test functions which either invoke each other, functions
that are already const-ified, or no further functions.

It is therefore relatively trivial to const-ify them, which provides a
basis for further const-ification further up the call stack.

Link: https://lkml.kernel.org/r/20250901205021.3573313-1-max.kellermann@ionos.com
Link: https://lkml.kernel.org/r/20250901205021.3573313-2-max.kellermann@ionos.com
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christian Zankel <chris@zankel.net>
Cc: David Rientjes <rientjes@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <james.bottomley@HansenPartnership.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Nysal Jan K.A" <nysal@linux.ibm.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russel King <linux@armlinux.org.uk>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h       |    8 ++++----
 include/linux/shmem_fs.h |    4 ++--
 mm/shmem.c               |    6 +++---
 3 files changed, 9 insertions(+), 9 deletions(-)

--- a/include/linux/mm.h~mm-constify-shmem-related-test-functions-for-improved-const-correctness
+++ a/include/linux/mm.h
@@ -995,11 +995,11 @@ static inline void vma_iter_set(struct v
  * The vma_is_shmem is not inline because it is used only by slow
  * paths in userfault.
  */
-bool vma_is_shmem(struct vm_area_struct *vma);
-bool vma_is_anon_shmem(struct vm_area_struct *vma);
+bool vma_is_shmem(const struct vm_area_struct *vma);
+bool vma_is_anon_shmem(const struct vm_area_struct *vma);
 #else
-static inline bool vma_is_shmem(struct vm_area_struct *vma) { return false; }
-static inline bool vma_is_anon_shmem(struct vm_area_struct *vma) { return false; }
+static inline bool vma_is_shmem(const struct vm_area_struct *vma) { return false; }
+static inline bool vma_is_anon_shmem(const struct vm_area_struct *vma) { return false; }
 #endif
 
 int vma_is_stack_for_current(struct vm_area_struct *vma);
--- a/include/linux/shmem_fs.h~mm-constify-shmem-related-test-functions-for-improved-const-correctness
+++ a/include/linux/shmem_fs.h
@@ -99,9 +99,9 @@ extern unsigned long shmem_get_unmapped_
 		unsigned long len, unsigned long pgoff, unsigned long flags);
 extern int shmem_lock(struct file *file, int lock, struct ucounts *ucounts);
 #ifdef CONFIG_SHMEM
-bool shmem_mapping(struct address_space *mapping);
+bool shmem_mapping(const struct address_space *mapping);
 #else
-static inline bool shmem_mapping(struct address_space *mapping)
+static inline bool shmem_mapping(const struct address_space *mapping)
 {
 	return false;
 }
--- a/mm/shmem.c~mm-constify-shmem-related-test-functions-for-improved-const-correctness
+++ a/mm/shmem.c
@@ -275,18 +275,18 @@ static const struct vm_operations_struct
 static const struct vm_operations_struct shmem_anon_vm_ops;
 static struct file_system_type shmem_fs_type;
 
-bool shmem_mapping(struct address_space *mapping)
+bool shmem_mapping(const struct address_space *mapping)
 {
 	return mapping->a_ops == &shmem_aops;
 }
 EXPORT_SYMBOL_GPL(shmem_mapping);
 
-bool vma_is_anon_shmem(struct vm_area_struct *vma)
+bool vma_is_anon_shmem(const struct vm_area_struct *vma)
 {
 	return vma->vm_ops == &shmem_anon_vm_ops;
 }
 
-bool vma_is_shmem(struct vm_area_struct *vma)
+bool vma_is_shmem(const struct vm_area_struct *vma)
 {
 	return vma_is_anon_shmem(vma) || vma->vm_ops == &shmem_vm_ops;
 }
_

Patches currently in -mm which might be from max.kellermann@ionos.com are

pagevech-add-const-to-pointer-parameters-of-getter-functions.patch
huge_mmh-disallow-is_huge_zero_folionull.patch
mm-constify-shmem-related-test-functions-for-improved-const-correctness.patch
mm-constify-pagemap-related-test-getter-functions.patch
mm-constify-zone-related-test-getter-functions.patch
fs-constify-mapping-related-test-functions-for-improved-const-correctness.patch
mm-constify-process_shares_mm-for-improved-const-correctness.patch
mm-s390-constify-mapping-related-test-getter-functions.patch
parisc-constify-mmap_upper_limit-parameter.patch
mm-constify-arch_pick_mmap_layout-for-improved-const-correctness.patch
mm-constify-ptdesc_pmd_pts_count-and-folio_get_private.patch
mm-constify-various-inline-functions-for-improved-const-correctness.patch
mm-constify-assert-test-functions-in-mmh.patch
mm-constify-highmem-related-functions-for-improved-const-correctness.patch