Re: [PATCH v2 5/7] mm/mglru: make LRU folio prefetch helper an inline function

[Lian Wang <lianux.mm@gmail.com>]

On Fri, 28 Aug 2026 07:47:02 +0800 "Barry Song (Xiaomi)" <baohua@kernel.org> wrote:

> `prefetchw_prev_lru_folio()` is currently implemented as a macro with a
> potentially unused argument. This makes the helper harder to read and can
> also trigger checkpatch warnings about unused macro arguments.
>
> Make it a `static inline` function and remove the unnecessary `_field`
> argument. The helper always prefetches the previous folio's `flags`, so
> there is no need to make the field configurable.
>
> Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
> Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
> ---
>  mm/vmscan.c | 26 +++++++++++++++-----------
>  1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2b33d3f44682..81f95a968447 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -182,17 +182,21 @@ struct scan_control {
>  };
>
>  #ifdef ARCH_HAS_PREFETCHW
> -#define prefetchw_prev_lru_folio(_folio, _base, _field)			\
> -	do {								\
> -		if ((_folio)->lru.prev != _base) {			\
> -			struct folio *prev;				\
> -									\
> -			prev = lru_to_folio(&(_folio->lru));		\
> -			prefetchw(&prev->_field);			\
> -		}							\
> -	} while (0)
> +static inline void prefetchw_prev_lru_folio(struct folio *folio,
> +		struct list_head *base)
> +{
> +	if (folio->lru.prev != base) {
> +		struct folio *prev;
> +
> +		prev = lru_to_folio(&folio->lru);
> +		prefetchw(&prev->flags);
> +	}
> +}
>  #else
> -#define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
> +static inline void prefetchw_prev_lru_folio(struct folio *folio,
> +		struct list_head *base)
> +{
> +}
>  #endif
>
>  /*
> @@ -1695,7 +1699,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
>  		struct folio *folio;
>
>  		folio = lru_to_folio(src);
> -		prefetchw_prev_lru_folio(folio, src, flags);
> +		prefetchw_prev_lru_folio(folio, src);
>
>  		nr_pages = folio_nr_pages(folio);
>  		total_scan += nr_pages;
> --
> 2.34.1

This preserves the prefetch behavior while making the helper
interface clearer. Looks good to me.

Reviewed-by: Lian Wang <lianux.mm@gmail.com>