Re: [PATCH mm-unstable v1] mm: add a total mapcount for large folios

[Matthew Wilcox]

On Wed, Aug 09, 2023 at 05:23:46PM -0400, Peter Xu wrote:
> Hi, David,
> 
> Some pure questions below..
> 
> On Wed, Aug 09, 2023 at 10:32:56AM +0200, David Hildenbrand wrote:
> > Let's track the total mapcount for all large folios in the first subpage.
> > 
> > The total mapcount is what we actually want to know in folio_mapcount()
> > and it is also sufficient for implementing folio_mapped(). This also
> > gets rid of any "raceiness" concerns as expressed in
> > folio_total_mapcount().
> 
> Any more information for that "raciness" described here?

UTSL.

        /*
         * Add all the PTE mappings of those pages mapped by PTE.
         * Limit the loop to folio_nr_pages_mapped()?
         * Perhaps: given all the raciness, that may be a good or a bad idea.
         */