Re: [PATCH v1 06/10] mm/huge_memory: remove folio split check for READ_ONLY_THP_FOR_FS

[Lorenzo Stoakes (Oracle)]

On Thu, Mar 26, 2026 at 09:42:51PM -0400, Zi Yan wrote:
> Without READ_ONLY_THP_FOR_FS, large file-backed folios cannot be created by
> a FS without large folio support. The check is no longer needed.
>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>

Seems legitimate, so:

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx>

> ---
>  mm/huge_memory.c | 22 ----------------------
>  1 file changed, 22 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 1da1467328a3..30eddcbf86f1 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -3732,28 +3732,6 @@ int folio_check_splittable(struct folio *folio, unsigned int new_order,
>  		/* order-1 is not supported for anonymous THP. */
>  		if (new_order == 1)
>  			return -EINVAL;
> -	} else if (split_type == SPLIT_TYPE_NON_UNIFORM || new_order) {
> -		if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
> -		    !mapping_large_folio_support(folio->mapping)) {
> -			/*
> -			 * We can always split a folio down to a single page
> -			 * (new_order == 0) uniformly.
> -			 *
> -			 * For any other scenario
> -			 *   a) uniform split targeting a large folio
> -			 *      (new_order > 0)
> -			 *   b) any non-uniform split
> -			 * we must confirm that the file system supports large
> -			 * folios.
> -			 *
> -			 * Note that we might still have THPs in such
> -			 * mappings, which is created from khugepaged when
> -			 * CONFIG_READ_ONLY_THP_FOR_FS is enabled. But in that
> -			 * case, the mapping does not actually support large
> -			 * folios properly.
> -			 */
> -			return -EINVAL;
> -		}
>  	}
>
>  	/*
> --
> 2.43.0
>