Re: [PATCH 1/9] mm, swap: use unified helper for swap cache look up

[Kairui Song <ryncsn@gmail.com>]

On Tue, Sep 2, 2025 at 6:13 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 22.08.25 21:20, Kairui Song wrote:
> > From: Kairui Song <kasong@tencent.com>
> >
> > Always use swap_cache_get_folio for swap cache folio look up. The reason
> > we are not using it in all places is that it also updates the readahead
> > info, and some callsites want to avoid that.
> >
> > So decouple readahead update with swap cache lookup into a standalone
> > helper, let the caller call the readahead update helper if that's
> > needed. And convert all swap cache lookups to use swap_cache_get_folio.
> >
> > After this commit, there are only three special cases for accessing swap
> > cache space now: huge memory splitting, migration and shmem replacing,
> > because they need to lock the Xarray. Following commits will wrap their
> > accesses to the swap cache too with special helpers.
> >
> > Signed-off-by: Kairui Song <kasong@tencent.com>
> > ---
>
>
>
> > +void swap_update_readahead(struct folio *folio,
> > +                        struct vm_area_struct *vma,
> > +                        unsigned long addr)
> >   {
>
> Oh, one thing. Regarding recent const-correctness discussions, "folio"
> should probably be const here.
>

Not here, swap_update_readahead does folio_test_clear_readahead so...

I'll try add const to other places where I see the folio is const,
thanks for the info!

> --
> Cheers
>
> David / dhildenb
>
>