Re: [PATCH 5/6] mm: move folio_index to mm/swap.h and remove no longer needed helper

[Matthew Wilcox <willy@infradead.org>]

On Mon, Apr 28, 2025 at 02:59:07AM +0800, Kairui Song wrote:
> +++ b/mm/swap.h
> @@ -50,6 +50,24 @@ static inline pgoff_t swap_cache_index(swp_entry_t entry)
>  	return swp_offset(entry) & SWAP_ADDRESS_SPACE_MASK;
>  }
>  
> +/**
> + * folio_index - File index of a folio.
> + * @folio: The folio.
> + *
> + * For a folio which is either in the page cache or the swap cache,
> + * return its index within the address_space it belongs to.  If you know
> + * the page is definitely in the page cache, you can look at the folio's
> + * index directly.
> + *
> + * Return: The index (offset in units of pages) of a folio in its file.
> + */
> +static inline pgoff_t folio_index(struct folio *folio)
> +{
> +	if (unlikely(folio_test_swapcache(folio)))
> +		return swap_cache_index(folio->swap);
> +	return folio->index;
> +}

I think the build warning can be cured by moving this outside
CONFIG_SWAP