Re: [PATCH v2] mm: Fix for negative counter: nr_file_hugepages

[Matthew Wilcox]

On Tue, Nov 07, 2023 at 10:18:05AM -0800, Stefan Roesch wrote:
> +++ b/mm/huge_memory.c
> @@ -2740,7 +2740,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
>  			if (folio_test_swapbacked(folio)) {
>  				__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS,
>  							-nr);
> -			} else {
> +			} else if (folio_test_pmd_mappable(folio)) {
>  				__lruvec_stat_mod_folio(folio, NR_FILE_THPS,
>  							-nr);
>  				filemap_nr_thps_dec(mapping);

As I said, we also need the folio_test_pmd_mappable() for swapbacked.
Not because there's currently a problem, but because we don't leave
landmines for other people to trip over in future!