Re: [PATCH v22 1/4] mm: add MAP_DROPPABLE for designating always lazily freeable mappings

[Jason A. Donenfeld]

On Thu, Jul 11, 2024 at 07:54:34PM +0200, Jason A. Donenfeld wrote:
> On Thu, Jul 11, 2024 at 07:27:27PM +0200, David Hildenbrand wrote:
> > > PG_owner_priv_1 maps to PG_swapcache? :)
> > 
> > Maybe the combination !swapbacked && swapcache could be used to indicate 
> > such folios. (we will never set swapbacked)
> > 
> > But likely we have to be a bit careful here. We don't want 
> > folio_test_swapcache() to return for folios that ... are not in the 
> > swapcache.
> 
> I was thinking that too, but I'm afraid it's going to be another
> whack-a-mole nightmare. Even for things like task_mmu in procfs that
> show stats, that's going to be wonky.
> 
> Any other flags we can overload that aren't going to be already used in
> our case?

PG_error / folio_set_error seems unused in the non-IO case.