linux-kernel - Re: [PATCH v5 06/12] mm, s390: constify mapping related test functions for improved const-correctness

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Message-ID: <ce720df8-cdf2-492a-9eeb-e7b643bffa91@redhat.com>
Date: Mon, 1 Sep 2025 15:54:25 +0200
From: David Hildenbrand <david@...hat.com>
To: Max Kellermann <max.kellermann@...os.com>, akpm@...ux-foundation.org,
 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,
 linux@...linux.org.uk, James.Bottomley@...senPartnership.com, deller@....de,
 agordeev@...ux.ibm.com, gerald.schaefer@...ux.ibm.com, hca@...ux.ibm.com,
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Subject: Re: [PATCH v5 06/12] mm, s390: constify mapping related test
 functions for improved const-correctness

On 01.09.25 14:30, Max Kellermann wrote:
> 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>

Also here, some getters hiding.

> ---
>   arch/s390/mm/mmap.c     |  2 +-
>   include/linux/mm.h      |  6 +++---
>   include/linux/pagemap.h |  2 +-
>   mm/util.c               | 11 ++++++-----
>   4 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
> index 547104ccc22a..c0f619fb9ab3 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 *const 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);

Should this also be *const ?

>   
>   /* 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);
>   


Dito.

>   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 1d35f9e1416e..968b58a97236 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);

And this one?

-- 
Cheers

David / dhildenb