Re: [PATCH v2 00/16] mm: remove is_swap_[pte, pmd]() + non-swap entries, introduce leaf entries

Kairui Song
2025-11-11T04:17:29Z

On Tue, Nov 11, 2025 at 8:09 AM Hugh Dickins <hughd@google.com> wrote:
> On Mon, 10 Nov 2025, Lorenzo Stoakes wrote:
> > On Mon, Nov 10, 2025 at 03:04:48AM -0800, Chris Li wrote:
> > >
> > > That is actually the reason to give the swap table change more
> > > priority. Just saying.
> >
> > I'm sorry but this is not a reasonable request. I am being as empathetic and
> > kind as I can be here, but this series is proceeding without arbitrary delay.
> >
> > I will do everything I can to accommodate any concerns or issues you may have
> > here _within reason_ :)
>
> But Lorenzo, have you even tested your series properly yet, with
> swapping and folio migration and huge pages and tmpfs under load?
> Please do.
>
> I haven't had time to bisect yet, maybe there's nothing more needed
> than a one-liner fix somewhere; but from my experience it is not yet
> ready for inclusion in mm and next - it stops testing other folks' work.
>
> I haven't tried today's v3, but from the cover letter of differences,
> it didn't look like much of importance is fixed since v2: which
> (after a profusion of "Bad swap offet entry 3ffffffffffff" messages,

I also noticed the 0x3fff... issue in V2:
https://lore.kernel.org/all/CAMgjq7AP383YfU3L5ZxJ9U3x-vRPnEkEUtmnPdXD29HiNC8OrA@mail.gmail.com/

The issue is caused by removing the pte_none check, that could result
in issues like this, so that check has to stay I think, at least for
the swap part.

It seems V3 has fixed it, I can have a try later.

I also hope we can keep the swap entry part untouched, Overloading
swap entry for things like migration looks odd indeed, but setting and
getting a PTE as swap entry seems clean and easy to understand.
Existing usage of swap entries is quite logically consistent and
stable, we might need to do some cleanup for swap but having a
standalone type and define is very helpful.