Re: [PATCH] mm: huge_memory: add the missing folio_test_pmd_mappable() for THP split statistics

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 2024/4/22 14:17, Lance Yang wrote:
> Hey Baolin,
> 
> Maybe I spotted a bug and made a change to this patch as follows.
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 824eff9211db..f3c4e08c6d30 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2994,6 +2994,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
>   	XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
>   	struct anon_vma *anon_vma = NULL;
>   	struct address_space *mapping = NULL;
> +	int order = folio_order(folio);
>   	int extra_pins, ret;
>   	pgoff_t end;
>   	bool is_hzp;
> @@ -3172,7 +3173,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
>   		i_mmap_unlock_read(mapping);
>   out:
>   	xas_destroy(&xas);
> -	if (folio_test_pmd_mappable(folio))
> 
> IIUC, if we split the folio successfully, it won’t be large here.

Yes, good catch. I did a blindly copy-paste.

Will fix in next version. Thanks for reviewing.

> +	if (order >= HPAGE_PMD_ORDER)
>   		count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
>   	return ret;
>   }
> 
> Thanks,
> Lance