linux-kernel - Re: [PATCH -next 8/9] mm: page_alloc: use a folio in free_pages

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Message-ID: <b7818a38-d991-6cdd-c908-fe0ebc3677c6@redhat.com>
Date:   Tue, 26 Sep 2023 09:49:16 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mike Rapoport <rppt@...nel.org>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, ying.huang@...el.com,
        Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH -next 8/9] mm: page_alloc: use a folio in
 free_pages_prepare()

On 26.09.23 02:52, Kefeng Wang wrote:
> The page should not a tail page in free_pages_prepare(), let's use
> a folio in free_pages_prepare() to save several compound_head() calls.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>   mm/page_alloc.c | 15 ++++++++-------
>   1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 06be8821d833..a888b9d57751 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1070,6 +1070,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
>   			unsigned int order, fpi_t fpi_flags)
>   {
>   	int bad = 0;
> +	struct folio *folio = page_folio(page);

We might have higher-order pages here that are not folios (not compound 
pages). It looks a bit like this function really shouldn't be working 
with folios in the generic way, for that reason.

Wrong level of abstraction in that function.

What am I missing?

-- 
Cheers,

David / dhildenb