Re: [PATCH v2 5/7] mm: task_mmu: use a folio in smaps_account()

[Kefeng Wang]

On 2023/11/11 2:29, Matthew Wilcox wrote:
> On Fri, Nov 10, 2023 at 11:33:22AM +0800, Kefeng Wang wrote:
> > Replace seven implicit calls to compound_head() with one page_folio().
>
> You're so focused on trying to accomplish your goal (killing off the
> page_idle and page_young functions) that you're doing a poor job thinkig
> about the conversions you're doing along the way.
>
> > +++ b/fs/proc/task_mmu.c
> > @@ -445,23 +445,25 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
> >   {
> >   	int i, nr = compound ? compound_nr(page) : 1;
> >   	unsigned long size = nr * PAGE_SIZE;
> > +	struct folio *folio = page_folio(page);
>
> Stop right here.  The use of compound_nr() should give you pause.
>
> After looking at how smaps_account() is used, it seems to me that the
> two callers should each pass in PAGE_SIZE or PMD_SIZE instead of doing
> this calculation.

Yes，this will save extra calculation

> More generally, step back from this series.  Do a good job of
> transforming fs/proc/task_mmu.c to use folios.  Once you've done
> that, you can approach the young/idle work again.
Thanks for you advise，will try this firstly.
>