Re: [PATCH mm-hotfixes] mm/huge_memory: fix memory corruption on huge zero page move

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 3 Mar 2026 07:25:32 +0000 Lorenzo Stoakes <lorenzo.stoakes@oracle.com> wrote:

> On Mon, Mar 02, 2026 at 12:50:32PM -0800, Andrew Morton wrote:
> > On Mon, 2 Mar 2026 17:19:15 +0000 Lorenzo Stoakes <lorenzo.stoakes@oracle.com> wrote:
> >
> > > On Mon, Mar 02, 2026 at 06:10:06PM +0100, David Hildenbrand (Arm) wrote:
> > > > There are already patches in flight:
> > > >
> > > > https://lore.kernel.org/r/aaBVaHs8rIkNcwM0@chrisdown.name
> > >
> > > Yup, if people would actually cc the right people I'd not have wasted my
> > > afternoon.
> > >
> > > Replying there.
> > >
> >
> > I'm not sure where this is headed but I'll queue this patch for now, to
> > get it some testing, to lessen duplicated bug reports and to generally track things.
> 
> Hi Andrew -

Who is a confused person!

> We should drop my patch and take Chris's.

"my patch" being "mm/huge_memory: fix memory corruption on huge zero
page move", I assume.

> However, life isn't so simple :) as there's been some confusion with his series
> since his email client seemed to mess up somehow and a couple patches need to be
> squashed on one another.
> 
> So to make life easier, I enclose a squashed patch (combining the commit
> message from both), with my R-b, T-b tags attached, please replace my patch
> with this one.

OK.  I added your signed-off-by also.

> Also, could you make this into a 2 patch series with
> https://lore.kernel.org/linux-mm/aaBWG4fajXXbjpVN@chrisdown.name/ _after_ this
> one?

Well, "mm/huge_memory: Fix use of NULL folio in move_pages_huge_pmd()"
is a cc:stable mm-hotfix and I don't think "selftests/mm: Add UFFDIO_MOVE
huge zeropage PMD regression test" is to be treated that way?

If correct, I'd keep "selftests/mm: Add UFFDIO_MOVE huge zeropage PMD
regression test" as a standalone singleton in mmm-unstable.

> mm-unstable (I'm not sure why we're rushing changes there so quick...) had
> _only_ this regression test patch in it, so we were left with a kernel that
> splatted on running mm selftests, which is not what we want.

But the regression fix "mm/huge_memory: fix memory corruption on huge
zero page move" was in mm-hotfixes, cc:stable?

> (It seems to me this is what mm-new is for, and it seems we have some holes in
> our testing still since this got thorugh).
> 
> Please drop the patch you have for this already in mm-unstable and make sure we
> only have it _after_ the fix is applied :)

I think you mean to drop "mm/huge_memory: fix memory corruption on huge
zero page move" from mm-hotfixes.


So we now have

"mm/huge_memory: fix use of NULL folio in move_pages_huge_pmd()" in
mm-hotfixes, cc:stable

"selftests/mm: add UFFDIO_MOVE huge zeropage PMD regression test" in
mm-unstable, not cc:stable.

btw, "selftests/mm: add UFFDIO_MOVE huge zeropage PMD regression test"
still has a bunch of unaddressed review comments from David.