[PATCH v6 02/13] mm: remove extra ZONE_DEVICE struct page refcount

[Christoph Hellwig]

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8ae31622deef..d48a1f0889d1 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1218,7 +1218,7 @@ __maybe_unused struct page *try_grab_compound_head(struct page *page, int refs,
>  static inline __must_check bool try_get_page(struct page *page)
>  {
>  	page = compound_head(page);
> -	if (WARN_ON_ONCE(page_ref_count(page) <= 0))
> +	if (WARN_ON_ONCE(page_ref_count(page) < (int)!is_zone_device_page(page)))

Please avoid the overly long line.  In fact I'd be tempted to just not
bother here and keep the old, more lose check.  Especially given that
John has a patch ready that removes try_get_page entirely.