Message-ID: <06b653a4-4584-4a39-af9e-2a93c75641a8@lucifer.local>
Date: Mon, 1 Sep 2025 15:09:56 +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 v5 02/12] mm: constify pagemap related test functions for
 improved const-correctness

On Mon, Sep 01, 2025 at 02:30:18PM +0200, 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.
>
> 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>

> ---
>  include/linux/pagemap.h | 57 +++++++++++++++++++++--------------------
>  1 file changed, 29 insertions(+), 28 deletions(-)
>
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index a3e16d74792f..1d35f9e1416e 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -140,7 +140,7 @@ static inline int inode_drain_writes(struct inode *inode)
>  	return filemap_write_and_wait(inode->i_mapping);
>  }
>
> -static inline bool mapping_empty(struct address_space *mapping)
> +static inline bool mapping_empty(const struct address_space *const mapping)
>  {
>  	return xa_empty(&mapping->i_pages);
>  }
> @@ -166,7 +166,7 @@ static inline bool mapping_empty(struct address_space *mapping)
>   * refcount and the referenced bit, which will be elevated or set in
>   * the process of adding new cache pages to an inode.
>   */
> -static inline bool mapping_shrinkable(struct address_space *mapping)
> +static inline bool mapping_shrinkable(const struct address_space *const mapping)
>  {
>  	void *head;
>
> @@ -267,7 +267,7 @@ static inline void mapping_clear_unevictable(struct address_space *mapping)
>  	clear_bit(AS_UNEVICTABLE, &mapping->flags);
>  }
>
> -static inline bool mapping_unevictable(struct address_space *mapping)
> +static inline bool mapping_unevictable(const struct address_space *const mapping)
>  {
>  	return mapping && test_bit(AS_UNEVICTABLE, &mapping->flags);
>  }
> @@ -277,7 +277,7 @@ static inline void mapping_set_exiting(struct address_space *mapping)
>  	set_bit(AS_EXITING, &mapping->flags);
>  }
>
> -static inline int mapping_exiting(struct address_space *mapping)
> +static inline int mapping_exiting(const struct address_space *const mapping)
>  {
>  	return test_bit(AS_EXITING, &mapping->flags);
>  }
> @@ -287,7 +287,7 @@ static inline void mapping_set_no_writeback_tags(struct address_space *mapping)
>  	set_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
>  }
>
> -static inline int mapping_use_writeback_tags(struct address_space *mapping)
> +static inline int mapping_use_writeback_tags(const struct address_space *const mapping)
>  {
>  	return !test_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
>  }
> @@ -333,7 +333,7 @@ static inline void mapping_set_inaccessible(struct address_space *mapping)
>  	set_bit(AS_INACCESSIBLE, &mapping->flags);
>  }
>
> -static inline bool mapping_inaccessible(struct address_space *mapping)
> +static inline bool mapping_inaccessible(const struct address_space *const mapping)
>  {
>  	return test_bit(AS_INACCESSIBLE, &mapping->flags);
>  }
> @@ -343,18 +343,18 @@ static inline void mapping_set_writeback_may_deadlock_on_reclaim(struct address_
>  	set_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
>  }
>
> -static inline bool mapping_writeback_may_deadlock_on_reclaim(struct address_space *mapping)
> +static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct address_space *const mapping)
>  {
>  	return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags);
>  }
>
> -static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
> +static inline gfp_t mapping_gfp_mask(const struct address_space *const mapping)
>  {
>  	return mapping->gfp_mask;
>  }
>
>  /* Restricts the given gfp_mask to what the mapping allows. */
> -static inline gfp_t mapping_gfp_constraint(struct address_space *mapping,
> +static inline gfp_t mapping_gfp_constraint(const struct address_space *mapping,
>  		gfp_t gfp_mask)
>  {
>  	return mapping_gfp_mask(mapping) & gfp_mask;
> @@ -477,13 +477,13 @@ mapping_min_folio_order(const struct address_space *mapping)
>  }
>
>  static inline unsigned long
> -mapping_min_folio_nrpages(struct address_space *mapping)
> +mapping_min_folio_nrpages(const struct address_space *const mapping)
>  {
>  	return 1UL << mapping_min_folio_order(mapping);
>  }
>
>  static inline unsigned long
> -mapping_min_folio_nrbytes(struct address_space *mapping)
> +mapping_min_folio_nrbytes(const struct address_space *const mapping)
>  {
>  	return mapping_min_folio_nrpages(mapping) << PAGE_SHIFT;
>  }
> @@ -497,7 +497,7 @@ mapping_min_folio_nrbytes(struct address_space *mapping)
>   * new folio to the page cache and need to know what index to give it,
>   * call this function.
>   */
> -static inline pgoff_t mapping_align_index(struct address_space *mapping,
> +static inline pgoff_t mapping_align_index(const struct address_space *const mapping,
>  					  pgoff_t index)
>  {
>  	return round_down(index, mapping_min_folio_nrpages(mapping));
> @@ -507,7 +507,7 @@ static inline pgoff_t mapping_align_index(struct address_space *mapping,
>   * Large folio support currently depends on THP.  These dependencies are
>   * being worked on but are not yet fixed.
>   */
> -static inline bool mapping_large_folio_support(struct address_space *mapping)
> +static inline bool mapping_large_folio_support(const struct address_space *mapping)
>  {
>  	/* AS_FOLIO_ORDER is only reasonable for pagecache folios */
>  	VM_WARN_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON,
> @@ -522,7 +522,7 @@ static inline size_t mapping_max_folio_size(const struct address_space *mapping)
>  	return PAGE_SIZE << mapping_max_folio_order(mapping);
>  }
>
> -static inline int filemap_nr_thps(struct address_space *mapping)
> +static inline int filemap_nr_thps(const struct address_space *const mapping)
>  {
>  #ifdef CONFIG_READ_ONLY_THP_FOR_FS
>  	return atomic_read(&mapping->nr_thps);
> @@ -936,7 +936,7 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
>   *
>   * Return: The index of the folio which follows this folio in the file.
>   */
> -static inline pgoff_t folio_next_index(struct folio *folio)
> +static inline pgoff_t folio_next_index(const struct folio *const folio)
>  {
>  	return folio->index + folio_nr_pages(folio);
>  }
> @@ -965,7 +965,7 @@ static inline struct page *folio_file_page(struct folio *folio, pgoff_t index)
>   * e.g., shmem did not move this folio to the swap cache.
>   * Return: true or false.
>   */
> -static inline bool folio_contains(struct folio *folio, pgoff_t index)
> +static inline bool folio_contains(const struct folio *const folio, pgoff_t index)
>  {
>  	VM_WARN_ON_ONCE_FOLIO(folio_test_swapcache(folio), folio);
>  	return index - folio->index < folio_nr_pages(folio);
> @@ -1042,13 +1042,13 @@ static inline loff_t page_offset(struct page *page)
>  /*
>   * Get the offset in PAGE_SIZE (even for hugetlb folios).
>   */
> -static inline pgoff_t folio_pgoff(struct folio *folio)
> +static inline pgoff_t folio_pgoff(const struct folio *const folio)
>  {
>  	return folio->index;
>  }
>
> -static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
> -					unsigned long address)
> +static inline pgoff_t linear_page_index(const struct vm_area_struct *const vma,
> +					const unsigned long address)
>  {
>  	pgoff_t pgoff;
>  	pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
> @@ -1468,7 +1468,7 @@ static inline unsigned int __readahead_batch(struct readahead_control *rac,
>   * readahead_pos - The byte offset into the file of this readahead request.
>   * @rac: The readahead request.
>   */
> -static inline loff_t readahead_pos(struct readahead_control *rac)
> +static inline loff_t readahead_pos(const struct readahead_control *const rac)
>  {
>  	return (loff_t)rac->_index * PAGE_SIZE;
>  }
> @@ -1477,7 +1477,7 @@ static inline loff_t readahead_pos(struct readahead_control *rac)
>   * readahead_length - The number of bytes in this readahead request.
>   * @rac: The readahead request.
>   */
> -static inline size_t readahead_length(struct readahead_control *rac)
> +static inline size_t readahead_length(const struct readahead_control *const rac)
>  {
>  	return rac->_nr_pages * PAGE_SIZE;
>  }
> @@ -1486,7 +1486,7 @@ static inline size_t readahead_length(struct readahead_control *rac)
>   * readahead_index - The index of the first page in this readahead request.
>   * @rac: The readahead request.
>   */
> -static inline pgoff_t readahead_index(struct readahead_control *rac)
> +static inline pgoff_t readahead_index(const struct readahead_control *const rac)
>  {
>  	return rac->_index;
>  }
> @@ -1495,7 +1495,7 @@ static inline pgoff_t readahead_index(struct readahead_control *rac)
>   * readahead_count - The number of pages in this readahead request.
>   * @rac: The readahead request.
>   */
> -static inline unsigned int readahead_count(struct readahead_control *rac)
> +static inline unsigned int readahead_count(const struct readahead_control *const rac)
>  {
>  	return rac->_nr_pages;
>  }
> @@ -1504,12 +1504,12 @@ static inline unsigned int readahead_count(struct readahead_control *rac)
>   * readahead_batch_length - The number of bytes in the current batch.
>   * @rac: The readahead request.
>   */
> -static inline size_t readahead_batch_length(struct readahead_control *rac)
> +static inline size_t readahead_batch_length(const struct readahead_control *const rac)
>  {
>  	return rac->_batch_count * PAGE_SIZE;
>  }
>
> -static inline unsigned long dir_pages(struct inode *inode)
> +static inline unsigned long dir_pages(const struct inode *const inode)
>  {
>  	return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
>  			       PAGE_SHIFT;
> @@ -1523,8 +1523,8 @@ static inline unsigned long dir_pages(struct inode *inode)
>   * Return: the number of bytes in the folio up to EOF,
>   * or -EFAULT if the folio was truncated.
>   */
> -static inline ssize_t folio_mkwrite_check_truncate(struct folio *folio,
> -					      struct inode *inode)
> +static inline ssize_t folio_mkwrite_check_truncate(const struct folio *const folio,
> +						   const struct inode *const inode)
>  {
>  	loff_t size = i_size_read(inode);
>  	pgoff_t index = size >> PAGE_SHIFT;
> @@ -1555,7 +1555,8 @@ static inline ssize_t folio_mkwrite_check_truncate(struct folio *folio,
>   * Return: The number of filesystem blocks covered by this folio.
>   */
>  static inline
> -unsigned int i_blocks_per_folio(struct inode *inode, struct folio *folio)
> +unsigned int i_blocks_per_folio(const struct inode *const inode,
> +				const struct folio *const folio)
>  {
>  	return folio_size(folio) >> inode->i_blkbits;
>  }
> --
> 2.47.2
>

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