Re: [PATCH v2 1/3] mm: workingset: use lruvec_page_state_local() to count lru pages

[Shakeel Butt <shakeel.butt@linux.dev>]

On Mon, Aug 31, 2026 at 05:46:09PM +0800, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@kylinos.cn>
> 
> Commit 7404bd37cfbe ("mm: workingset: use lruvec_lru_size() to get the
> number of lru pages") switched count_shadow_nodes() to lruvec_lru_size().
> With CONFIG_MEMCG enabled, lruvec_lru_size() reads mz->lru_zone_size,
> which only the classic LRU paths maintain.  MGLRU accounts its pages
> through __update_lru_size(), which skips that array, so with MGLRU on the
> four evictable LRU lists are always seen as empty.  The shadow node budget
> (pages >> 3) then collapses to slab plus unevictable pages, and the
> workingset shadow shrinker reclaims eviction tokens almost as fast as they
> are created, losing thrashing protection.
> 
> lruvec_page_state_local() reads lruvec_stats->state_local instead, which
> both classic LRU and MGLRU maintain.  Switch back to it.  The reparenting
> race this re-exposes on cgroup v2 is closed by the follow-up patch that
> redirects dying-memcg stat updates for all hierarchies.
> 
> Fixes: 7404bd37cfbe ("mm: workingset: use lruvec_lru_size() to get the number of lru pages")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>

Make this patch at the end (or after 2nd) of the series as it is only correct
after the 2nd patch of the series.

> ---
>  mm/workingset.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/workingset.c b/mm/workingset.c
> index f351798e723a..85a4e14e95d5 100644
> --- a/mm/workingset.c
> +++ b/mm/workingset.c
> @@ -693,10 +693,9 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
>  
>  		mem_cgroup_flush_stats_ratelimited(sc->memcg);
>  		lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid));
> -
>  		for (pages = 0, i = 0; i < NR_LRU_LISTS; i++)
> -			pages += lruvec_lru_size(lruvec, i, MAX_NR_ZONES - 1);
> -
> +			pages += lruvec_page_state_local(lruvec,
> +							 NR_LRU_BASE + i);
>  		pages += lruvec_page_state_local(
>  			lruvec, NR_SLAB_RECLAIMABLE_B) >> PAGE_SHIFT;
>  		pages += lruvec_page_state_local(
> -- 
> 2.53.0
>