Re: [PATCH v2 2/3] mm/huge_memory: allow split shmem large folio to any lower order

[Yang Shi <yang@os.amperecomputing.com>]

On 1/22/25 8:19 AM, Zi Yan wrote:
> Commit 4d684b5f92ba ("mm: shmem: add large folio support for tmpfs") has
> added large folio support to shmem. Remove the restriction in
> split_huge_page*().

Reviewed-by: Yang Shi <yang@os.amperecomputing.com>

>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>   mm/huge_memory.c | 8 +-------
>   1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 3d3ebdc002d5..deb4e72daeb9 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -3299,7 +3299,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
>   		/* Some pages can be beyond EOF: drop them from page cache */
>   		if (tail->index >= end) {
>   			if (shmem_mapping(folio->mapping))
> -				nr_dropped++;
> +				nr_dropped += new_nr;
>   			else if (folio_test_clear_dirty(tail))
>   				folio_account_cleaned(tail,
>   					inode_to_wb(folio->mapping->host));
> @@ -3465,12 +3465,6 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
>   			return -EINVAL;
>   		}
>   	} else if (new_order) {
> -		/* Split shmem folio to non-zero order not supported */
> -		if (shmem_mapping(folio->mapping)) {
> -			VM_WARN_ONCE(1,
> -				"Cannot split shmem folio to non-0 order");
> -			return -EINVAL;
> -		}
>   		/*
>   		 * No split if the file system does not support large folio.
>   		 * Note that we might still have THPs in such mappings due to