Re: [PATCH 3/3] mm: remove page_mapped()

[Matthew Wilcox]

On Mon, Apr 27, 2026 at 07:42:46AM -0700, Breno Leitao wrote:
> > > @@ -1353,7 +1353,7 @@ static bool panic_on_unrecoverable_mf(un
> > >  		cpu_relax();
> > >  		return page_count(p) == 0 &&
> > >  		       !PageLRU(p) &&
> > > -		       !page_mapped(p) &&
> > > +		       !folio_mapped(page_folio(p)) &&
> > >  		       !page_folio(p)->mapping &&
> > 
> > If we have a folio, we should really lookup the folio once. Not 4 times.
> 
> Why 4 times?

Because there are page_folio() calls hidden in PageLRU, page_mapped()
and page_count().

> > Breno's patch likely needs some love. :)
> 
> Would something like the following give it all the love in the world?
> 
>  folio = page_folio(p);
>  return page_count(p) == 0 &&
>         !PageLRU(p) &&
>         !folio_mapped(folio) &&
>         !folio->mapping &&
>         !is_free_buddy_page(p);

No.  You need to immerse yourself more deeply in the folio transition
;-)