Re: [PATCH] mm/rmap: do __folio_mod_stat() in __folio_add_rmap()

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Mon, Aug 04, 2025 at 06:41:06AM +0000, Wei Yang wrote:
> It is required to modify folio statistic after rmap changes, so it looks
> reasonable to do it in __folio_add_rmap(), which is the current behavior
> of __folio_remove_rmap() and folio_add_new_anon_rmap().
>
> Call __folio_mod_stat() in __folio_add_rmap(), so that rmap adjustment
> family shares the same pattern.

>
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

This is fine.

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

> Cc: David Hildenbrand <david@redhat.com>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Cc: Rik van Riel <riel@surriel.com>
> Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Harry Yoo <harry.yoo@oracle.com>
> ---
>  mm/rmap.c | 67 +++++++++++++++++++++++++------------------------------
>  1 file changed, 31 insertions(+), 36 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 568198e9efc2..84a8d8b02ef7 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1241,13 +1241,35 @@ int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
>  	return page_vma_mkclean_one(&pvmw);
>  }
>
> -static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
> +static void __folio_mod_stat(struct folio *folio, int nr, int nr_pmdmapped)
> +{
> +	int idx;
> +
> +	if (nr) {
> +		idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
> +		__lruvec_stat_mod_folio(folio, idx, nr);
> +	}
> +	if (nr_pmdmapped) {
> +		if (folio_test_anon(folio)) {
> +			idx = NR_ANON_THPS;
> +			__lruvec_stat_mod_folio(folio, idx, nr_pmdmapped);
> +		} else {
> +			/* NR_*_PMDMAPPED are not maintained per-memcg */
> +			idx = folio_test_swapbacked(folio) ?
> +				NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED;
> +			__mod_node_page_state(folio_pgdat(folio), idx,
> +					      nr_pmdmapped);
> +		}
> +	}
> +}
> +
> +static __always_inline void __folio_add_rmap(struct folio *folio,
>  		struct page *page, int nr_pages, struct vm_area_struct *vma,
> -		enum rmap_level level, int *nr_pmdmapped)
> +		enum rmap_level level)
>  {
>  	atomic_t *mapped = &folio->_nr_pages_mapped;
>  	const int orig_nr_pages = nr_pages;
> -	int first = 0, nr = 0;
> +	int first = 0, nr = 0, nr_pmdmapped = 0;
>
>  	__folio_rmap_sanity_checks(folio, page, nr_pages, level);
>
> @@ -1283,7 +1305,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
>  		first = atomic_inc_and_test(&folio->_entire_mapcount);
>  		if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) {
>  			if (level == RMAP_LEVEL_PMD && first)
> -				*nr_pmdmapped = folio_large_nr_pages(folio);
> +				nr_pmdmapped = folio_large_nr_pages(folio);
>  			nr = folio_inc_return_large_mapcount(folio, vma);
>  			if (nr == 1)
>  				/* Was completely unmapped. */
> @@ -1302,7 +1324,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
>  				 * folios separately.
>  				 */
>  				if (level == RMAP_LEVEL_PMD)
> -					*nr_pmdmapped = nr_pages;
> +					nr_pmdmapped = nr_pages;
>  				nr = nr_pages - (nr & FOLIO_PAGES_MAPPED);
>  				/* Raced ahead of a remove and another add? */
>  				if (unlikely(nr < 0))
> @@ -1315,7 +1337,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
>  		folio_inc_large_mapcount(folio, vma);
>  		break;
>  	}
> -	return nr;
> +	__folio_mod_stat(folio, nr, nr_pmdmapped);
>  }
>
>  /**
> @@ -1403,43 +1425,19 @@ static void __page_check_anon_rmap(const struct folio *folio,
>  		       page);
>  }
>
> -static void __folio_mod_stat(struct folio *folio, int nr, int nr_pmdmapped)
> -{
> -	int idx;
> -
> -	if (nr) {
> -		idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
> -		__lruvec_stat_mod_folio(folio, idx, nr);
> -	}
> -	if (nr_pmdmapped) {
> -		if (folio_test_anon(folio)) {
> -			idx = NR_ANON_THPS;
> -			__lruvec_stat_mod_folio(folio, idx, nr_pmdmapped);
> -		} else {
> -			/* NR_*_PMDMAPPED are not maintained per-memcg */
> -			idx = folio_test_swapbacked(folio) ?
> -				NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED;
> -			__mod_node_page_state(folio_pgdat(folio), idx,
> -					      nr_pmdmapped);
> -		}
> -	}
> -}
> -
>  static __always_inline void __folio_add_anon_rmap(struct folio *folio,
>  		struct page *page, int nr_pages, struct vm_area_struct *vma,
>  		unsigned long address, rmap_t flags, enum rmap_level level)
>  {
> -	int i, nr, nr_pmdmapped = 0;
> +	int i;
>
>  	VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
>
> -	nr = __folio_add_rmap(folio, page, nr_pages, vma, level, &nr_pmdmapped);
> +	__folio_add_rmap(folio, page, nr_pages, vma, level);
>
>  	if (likely(!folio_test_ksm(folio)))
>  		__page_check_anon_rmap(folio, page, vma, address);
>
> -	__folio_mod_stat(folio, nr, nr_pmdmapped);
> -
>  	if (flags & RMAP_EXCLUSIVE) {
>  		switch (level) {
>  		case RMAP_LEVEL_PTE:
> @@ -1613,12 +1611,9 @@ static __always_inline void __folio_add_file_rmap(struct folio *folio,
>  		struct page *page, int nr_pages, struct vm_area_struct *vma,
>  		enum rmap_level level)
>  {
> -	int nr, nr_pmdmapped = 0;
> -
>  	VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
>
> -	nr = __folio_add_rmap(folio, page, nr_pages, vma, level, &nr_pmdmapped);
> -	__folio_mod_stat(folio, nr, nr_pmdmapped);
> +	__folio_add_rmap(folio, page, nr_pages, vma, level);
>
>  	/* See comments in folio_add_anon_rmap_*() */
>  	if (!folio_test_large(folio))
> --
> 2.34.1
>
>