linux-kernel - Re: [PATCH v6 06/12] mm, s390: constify mapping related test/getter functions

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Message-ID: <0d709350-3016-4676-8b13-3fe5dda916f4@lucifer.local>
Date: Tue, 2 Sep 2025 07:13:34 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Max Kellermann <max.kellermann@...os.com>
Cc: akpm@...ux-foundation.org, david@...hat.com, axelrasmussen@...gle.com,
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Subject: Re: [PATCH v6 06/12] mm, s390: constify mapping related test/getter
 functions

On Mon, Sep 01, 2025 at 10:50:15PM +0200, Max Kellermann wrote:
> For improved const-correctness.
>
> 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.
>
> (Even though seemingly unrelated, this also constifies the pointer
> parameter of mmap_is_legacy() in arch/s390/mm/mmap.c because a copy of
> the function exists in mm/util.c.)
>
> Signed-off-by: Max Kellermann <max.kellermann@...os.com>
> Reviewed-by: Vishal Moola (Oracle) <vishal.moola@...il.com>

LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  arch/s390/mm/mmap.c     |  2 +-
>  include/linux/mm.h      |  6 +++---
>  include/linux/pagemap.h |  2 +-
>  mm/util.c               | 10 +++++-----
>  4 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
> index 547104ccc22a..e188cb6d4946 100644
> --- a/arch/s390/mm/mmap.c
> +++ b/arch/s390/mm/mmap.c
> @@ -27,7 +27,7 @@ static unsigned long stack_maxrandom_size(void)
>  	return STACK_RND_MASK << PAGE_SHIFT;
>  }
>
> -static inline int mmap_is_legacy(struct rlimit *rlim_stack)
> +static inline int mmap_is_legacy(const struct rlimit *rlim_stack)
>  {
>  	if (current->personality & ADDR_COMPAT_LAYOUT)
>  		return 1;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index f70c6b4d5f80..23864c3519d6 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -986,7 +986,7 @@ 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);
> +int vma_is_stack_for_current(const struct vm_area_struct *vma);
>
>  /* flush_tlb_range() takes a vma, not a mm, and can care about flags */
>  #define TLB_FLUSH_VMA(mm,flags) { .vm_mm = (mm), .vm_flags = (flags) }
> @@ -2585,7 +2585,7 @@ void folio_add_pin(struct folio *folio);
>
>  int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc);
>  int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
> -			struct task_struct *task, bool bypass_rlim);
> +			const struct task_struct *task, bool bypass_rlim);
>
>  struct kvec;
>  struct page *get_dump_page(unsigned long addr, int *locked);
> @@ -3348,7 +3348,7 @@ void anon_vma_interval_tree_verify(struct anon_vma_chain *node);
>  	     avc; avc = anon_vma_interval_tree_iter_next(avc, start, last))
>
>  /* mmap.c */
> -extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin);
> +extern int __vm_enough_memory(const struct mm_struct *mm, long pages, int cap_sys_admin);
>  extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
>  extern void exit_mmap(struct mm_struct *);
>  bool mmap_read_lock_maybe_expand(struct mm_struct *mm, struct vm_area_struct *vma,
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 1d3803c397e9..185644e288ea 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -551,7 +551,7 @@ static inline void filemap_nr_thps_dec(struct address_space *mapping)
>  #endif
>  }
>
> -struct address_space *folio_mapping(struct folio *);
> +struct address_space *folio_mapping(const struct folio *folio);
>
>  /**
>   * folio_flush_mapping - Find the file mapping this folio belongs to.
> diff --git a/mm/util.c b/mm/util.c
> index d235b74f7aff..241d2eaf26ca 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -315,7 +315,7 @@ void *memdup_user_nul(const void __user *src, size_t len)
>  EXPORT_SYMBOL(memdup_user_nul);
>
>  /* Check if the vma is being used as a stack by this task */
> -int vma_is_stack_for_current(struct vm_area_struct *vma)
> +int vma_is_stack_for_current(const struct vm_area_struct *vma)
>  {
>  	struct task_struct * __maybe_unused t = current;
>
> @@ -410,7 +410,7 @@ unsigned long arch_mmap_rnd(void)
>  	return rnd << PAGE_SHIFT;
>  }
>
> -static int mmap_is_legacy(struct rlimit *rlim_stack)
> +static int mmap_is_legacy(const struct rlimit *rlim_stack)
>  {
>  	if (current->personality & ADDR_COMPAT_LAYOUT)
>  		return 1;
> @@ -504,7 +504,7 @@ EXPORT_SYMBOL_IF_KUNIT(arch_pick_mmap_layout);
>   * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
>   */
>  int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
> -			struct task_struct *task, bool bypass_rlim)
> +			const struct task_struct *task, bool bypass_rlim)
>  {
>  	unsigned long locked_vm, limit;
>  	int ret = 0;
> @@ -688,7 +688,7 @@ struct anon_vma *folio_anon_vma(const struct folio *folio)
>   * You can call this for folios which aren't in the swap cache or page
>   * cache and it will return NULL.
>   */
> -struct address_space *folio_mapping(struct folio *folio)
> +struct address_space *folio_mapping(const struct folio *folio)
>  {
>  	struct address_space *mapping;
>
> @@ -926,7 +926,7 @@ EXPORT_SYMBOL_GPL(vm_memory_committed);
>   * Note this is a helper function intended to be used by LSMs which
>   * wish to use this logic.
>   */
> -int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> +int __vm_enough_memory(const struct mm_struct *mm, long pages, int cap_sys_admin)
>  {
>  	long allowed;
>  	unsigned long bytes_failed;
> --
> 2.47.2
>