Re: [PATCH -next 8/9] mm: page_alloc: use a folio in free_pages_prepare()

[Kefeng Wang]

On 2023/9/26 15:49, David Hildenbrand wrote:
> 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@xxxxxxxxxx>
> > ---
> >   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.

Thanks for your point this, also the change also looks unnecessary too,
the main purpose to use a folio in this function is prepared for
converting page_cpupid_reset_last() to folio, as the higher-order pages
the next patch is not right, I will reconsider it.

> What am I missing?