Re: [PATCH 1/9] mm: Always initialise folio->_deferred_list

[Miaohe Lin <linmiaohe@huawei.com>]

On 2024/3/21 22:24, Matthew Wilcox (Oracle) wrote:
> For compound pages which are at least order-2 (and hence have a
> deferred_list), initialise it and then we can check at free that the
> page is not part of a deferred list.  We recently found this useful to
> rule out a source of corruption.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  mm/huge_memory.c | 2 --
>  mm/hugetlb.c     | 3 ++-
>  mm/internal.h    | 2 ++
>  mm/memcontrol.c  | 2 ++
>  mm/page_alloc.c  | 9 +++++----
>  5 files changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 9859aa4f7553..04fb994a7b0b 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -792,8 +792,6 @@ void folio_prep_large_rmappable(struct folio *folio)
>  {
>  	if (!folio || !folio_test_large(folio))
>  		return;
> -	if (folio_order(folio) > 1)
> -		INIT_LIST_HEAD(&folio->_deferred_list);
>  	folio_set_large_rmappable(folio);
>  }
>  
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 23ef240ba48a..7e9a766059aa 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1796,7 +1796,8 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
>  		destroy_compound_gigantic_folio(folio, huge_page_order(h));
>  		free_gigantic_folio(folio, huge_page_order(h));
>  	} else {
> -		__free_pages(&folio->page, huge_page_order(h));
> +		INIT_LIST_HEAD(&folio->_deferred_list);

Will it be better to add a comment to explain why INIT_LIST_HEAD is needed ?

> +		folio_put(folio);

Can all __free_pages be replaced with folio_put in mm/hugetlb.c?

Thanks.