Re: [PATCH 05/20] mm/migrate: Convert expected_page_refs() to folio_expected_refs()

[Brian Foster]

On Mon, Jun 06, 2022 at 09:40:35PM +0100, Matthew Wilcox (Oracle) wrote:
> Now that both callers have a folio, convert this function to
> take a folio & rename it.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> ---
>  mm/migrate.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 77b8c662c9ca..e0a593e5b5f9 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -337,13 +337,18 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
>  }
>  #endif
>  
> -static int expected_page_refs(struct address_space *mapping, struct page *page)
> +static int folio_expected_refs(struct address_space *mapping,
> +		struct folio *folio)
>  {
> -	int expected_count = 1;
> +	int refs = 1;
> +	if (!mapping)
> +		return refs;
>  
> -	if (mapping)
> -		expected_count += compound_nr(page) + page_has_private(page);
> -	return expected_count;
> +	refs += folio_nr_pages(folio);
> +	if (folio_get_private(folio))
> +		refs++;

Why not folio_has_private() (as seems to be used for later
page_has_private() conversions) here?

> +
> +	return refs;;

Nit: extra ;

Brian

>  }
>  
>  /*
> @@ -360,7 +365,7 @@ int folio_migrate_mapping(struct address_space *mapping,
>  	XA_STATE(xas, &mapping->i_pages, folio_index(folio));
>  	struct zone *oldzone, *newzone;
>  	int dirty;
> -	int expected_count = expected_page_refs(mapping, &folio->page) + extra_count;
> +	int expected_count = folio_expected_refs(mapping, folio) + extra_count;
>  	long nr = folio_nr_pages(folio);
>  
>  	if (!mapping) {
> @@ -670,7 +675,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
>  		return migrate_page(mapping, &dst->page, &src->page, mode);
>  
>  	/* Check whether page does not have extra refs before we do more work */
> -	expected_count = expected_page_refs(mapping, &src->page);
> +	expected_count = folio_expected_refs(mapping, src);
>  	if (folio_ref_count(src) != expected_count)
>  		return -EAGAIN;
>  
> -- 
> 2.35.1
> 
>