Re: [PATCH] mm: dax: add comment for PFN_SPECIAL

[Dan Williams]

On Thu, Sep 27, 2018 at 12:39 PM <yang.shi@xxxxxxxxxxxxxxxxx> wrote:
>
> The comment for PFN_SPECIAL is missed in pfn_t.h. Add comment to get
> consistent with other pfn flags.
>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> ---
>  include/linux/pfn_t.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/pfn_t.h b/include/linux/pfn_t.h
> index 21713dc..d2e5dd4 100644
> --- a/include/linux/pfn_t.h
> +++ b/include/linux/pfn_t.h
> @@ -9,6 +9,7 @@
>   * PFN_SG_LAST - pfn references a page and is the last scatterlist entry
>   * PFN_DEV - pfn is not covered by system memmap by default
>   * PFN_MAP - pfn has a dynamic page mapping established by a device driver
> + * PFN_SPECIAL - indicates that _PAGE_SPECIAL should be used for DAX ptes

That's not quite accurate, I would change this to:

PFN_SPECIAL - for CONFIG_FS_DAX_LIMITED builds to allow XIP, but not
get_user_pages.