On Tue, Aug 05, 2025 at 05:11:49PM -0700, Boris Burkov wrote:
> If cgroups are configured into the kernel, then uncharged pages can only
> come from filemap_add_folio_nocharge. Track such uncharged folios in
> vmstat so that they are accounted for.
>
> Suggested-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Signed-off-by: Boris Burkov <boris@xxxxxx>
> ---
> include/linux/mmzone.h | 3 +++
> mm/filemap.c | 18 ++++++++++++++++++
> mm/vmstat.c | 3 +++
> 3 files changed, 24 insertions(+)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 283913d42d7b..a945dec65371 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -241,6 +241,9 @@ enum node_stat_item {
> NR_HUGETLB,
> #endif
> NR_BALLOON_PAGES,
> +#ifdef CONFIG_MEMCG
> + NR_UNCHARGED_FILE_PAGES,
> +#endif
> NR_VM_NODE_STAT_ITEMS
> };
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index ccc9cfb4d418..0a258b4a9246 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -146,6 +146,22 @@ static void page_cache_delete(struct address_space *mapping,
> mapping->nrpages -= nr;
> }
>
> +#ifdef CONFIG_MEMCG
> +static void filemap_mod_uncharged_vmstat(struct folio *folio, int sign)
> +{
> + long nr = folio_nr_pages(folio) * sign;
> +
> + if (!folio_memcg(folio))
> + __lruvec_stat_mod_folio(folio, NR_UNCHARGED_FILE_PAGES, nr);
