Re: [RFC PATCH 1/3] mm: Constify folio_mapping() and swapcache_mapping()

[Shivank Garg <shivankg@amd.com>]

On 2/11/2025 2:51 AM, Matthew Wilcox (Oracle) wrote:
> Neither of these functions modify their argument; make it const
> so the compiler knows this and can optimise accordingly.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  include/linux/pagemap.h | 4 ++--
>  mm/debug.c              | 2 +-
>  mm/swapfile.c           | 2 +-
>  mm/util.c               | 2 +-
>  4 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 47bfc6b1b632..8a9b2d201706 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -532,8 +532,8 @@ static inline void filemap_nr_thps_dec(struct address_space *mapping)
>  #endif
>  }
>  
> -struct address_space *folio_mapping(struct folio *);
> -struct address_space *swapcache_mapping(struct folio *);
> +struct address_space *folio_mapping(const struct folio *);
> +struct address_space *swapcache_mapping(const struct folio *);
>  
>  /**
>   * folio_file_mapping - Find the mapping this folio belongs to.
> diff --git a/mm/debug.c b/mm/debug.c
> index 8d2acf432385..fa3d9686034c 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -67,7 +67,7 @@ static const char *page_type_name(unsigned int page_type)
>  	return page_type_names[i];
>  }
>  
> -static void __dump_folio(struct folio *folio, struct page *page,
> +static void __dump_folio(const struct folio *folio, struct page *page,
>  		unsigned long pfn, unsigned long idx)
>  {
>  	struct address_space *mapping = folio_mapping(folio);
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 6e867c16ea93..ccaed8c2f761 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -3658,7 +3658,7 @@ struct swap_info_struct *swp_swap_info(swp_entry_t entry)
>  /*
>   * out-of-line methods to avoid include hell.
>   */
> -struct address_space *swapcache_mapping(struct folio *folio)
> +struct address_space *swapcache_mapping(const struct folio *folio)
>  {
>  	return swp_swap_info(folio->swap)->swap_file->f_mapping;
>  }
> diff --git a/mm/util.c b/mm/util.c
> index b6b9684a1438..682ecdb1b1c2 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -845,7 +845,7 @@ 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;
>  
This patch looks good to me.
Please consider

Reviewed-by: Shivank Garg <shivankg@amd.com>

Thanks,
Shivank