Re: [PATCH RFC 12/15] mm/smap: report workingset folios as referenced

[Johannes Weiner <hannes@cmpxchg.org>]

On Tue, Aug 04, 2026 at 03:47:08AM +0800, Kairui Song via B4 Relay wrote:
> @@ -944,6 +944,22 @@ static void smaps_page_accumulate(struct mem_size_stats *mss,
>  	}
>  }
>  
> +static bool smap_check_folio_referenced(struct folio *folio)
> +{
> +	if (lru_gen_enabled())
> +		return folio_is_referenced(folio);
> +	else
> +		return folio_is_referenced_by_bit(folio);
> +}
> +
> +static void smap_clear_folio_referenced(struct folio *folio)
> +{
> +	if (lru_gen_enabled())
> +		folio_set_lru_refs(folio, 0);
> +	else
> +		folio_clear_referenced_by_bit(folio);
> +}

I don't really understand this and the preceding 2 patches.

What is the benefit of a "shared" ref/workingset state implementation
when you then still have separate APIs for querying & modifying?

Switching some these callers from folio_test_workingset() to
folio_is_workingset()? But both functions continue to exist?

Why not make versions of folio_test_workingset(),
folio_test_referenced(), folio_clear_referenced() etc. that do the
arbitration (bit ops on classic, refs ops on mglru) and leave callers
that are only interested in boolean states, like here, alone?

folio_test_anon(), folio_test_lazyfree(), folio_test_swapcache() -
there are many examples where they don't just test a raw bit but
assess more complex, composed state.