Re: [PATCH v1] mm: remove total_mapcount()

[David Hildenbrand]

On 22.02.24 18:13, Matthew Wilcox wrote:
> On Thu, Feb 22, 2024 at 05:09:43PM +0100, David Hildenbrand wrote:
> > We always get a head page, so we can just naturally interpret is as a folio
> > (similar to other code).
>
> memfd seems rather confused about how to iterate over the page cache.
> Perhaps we could sort that out and then delete total_mapcount as a
> second patch?
>
> I haven't tested this at all, but ...
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
>
> diff --git a/mm/memfd.c b/mm/memfd.c
> index d3a1ba4208c9..45e55b0e3cbe 100644
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -29,28 +29,29 @@
>   #define MEMFD_TAG_PINNED        PAGECACHE_TAG_TOWRITE
>   #define LAST_SCAN               4       /* about 150ms max */
>   
> +static bool memfd_extra_refs(struct folio *folio)
> +{
> +	return folio_ref_count(folio) - folio_mapcount(folio) !=
> +		folio_nr_pages(folio);
> +}

That is an obvious improvement I should have realized myself.

Let me play with that.

Thanks!

--
Cheers,

David / dhildenb