mm: constify shmem related test functions for improved const-correctness

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>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
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: 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>

3 files changed, 9 insertions, 9 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b26ca8b2162d..45a47b555499 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -995,11 +995,11 @@ static inline void vma_iter_set(struct vma_iterator *vmi, unsigned long addr)
  * 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);
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 6d0f9c599ff7..0e47465ef0fd 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -99,9 +99,9 @@ extern unsigned long shmem_get_unmapped_area(struct file *, unsigned long addr,
 		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;
 }
diff --git a/mm/shmem.c b/mm/shmem.c
index 640fecc42f60..2df26f4d6e60 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -275,18 +275,18 @@ static const struct vm_operations_struct shmem_vm_ops;
 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;
 }