[RFC PATCH v2 1/8] ext4/xfs: add page refcount helper

[Matthew Wilcox]

On Mon, Jun 07, 2021 at 03:42:19PM -0500, Alex Sierra wrote:
> +++ b/include/linux/dax.h
> @@ -243,6 +243,16 @@ static inline bool dax_mapping(struct address_space *mapping)
>  	return mapping->host && IS_DAX(mapping->host);
>  }
>  
> +static inline bool dax_layout_is_idle_page(struct page *page)
> +{
> +	return page_ref_count(page) == 1;
> +}

We already have something called an idle page, and that's quite a
different thing from this.  How about dax_page_unused() (it's a use
count, so once it's got down to its minimum value, it's unused)?