On Tue, 13 Dec 2022 14:40:41 +0000 Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> On Tue, Dec 13, 2022 at 05:27:31PM +0800, Kefeng Wang wrote:
> > -struct page *damon_get_page(unsigned long pfn)
> > +struct folio *damon_get_folio(unsigned long pfn)
> > {
> > - struct page *page = pfn_to_online_page(pfn);
> > + struct folio *folio = pfn_to_online_folio(pfn);
> >
> > - if (!page || !PageLRU(page) || !get_page_unless_zero(page))
> > + if (!folio || !folio_test_lru(folio) || !folio_try_get(folio))
> > return NULL;
>
> Well, this is awkward. I asked Vishal to think about exactly this problem
> and we were going to talk about it after we're both back from vacation
> in January. But I guess we're going to do this in public instead ...
>
> Specifically, what should the semantics be for a putative
> damon_get_folio() when it encounters a tail page? Should it return
> the containing folio, or should it return NULL? And if the semantics
> change here to return the containing folio, what adjustments need to
> be made to the callers?
I'd prefer to simply keep the original behavior, returning NULL, for now unless
someone complaints.
Thanks,
SJ
