Re: [PATCH] mm/memory: Fix missing pte marker for !page on pte zaps

David Hildenbrand
2024-03-13T22:29:43Z

On 13.03.24 23:26, Peter Xu wrote:
> On Wed, Mar 13, 2024 at 11:03:04PM +0100, David Hildenbrand wrote:
>> On 13.03.24 22:31, peterx@redhat.com wrote:
>>> From: Peter Xu <peterx@redhat.com>
>>>
>>> Commit 0cf18e839f64 of large folio zap work broke uffd-wp. Now mm's uffd
>>> unit test "wp-unpopulated" will trigger this WARN_ON_ONCE().
>>
>> Good that I added the WARN_ON_ONCE() :)
>
> To be explict, VM_WARN_ON_ONCE. :) And that's my guess that you didn't hit
> it when you posted the series and did the tests, as I know latest distros
> like Fedora dropped DEBUG_VM, so maybe you had your base config out of
> there (but I normally have it irrelevant of that).

It's rather surprising that this went unnoticed for quite a while. I
usually do run with DEBUG_VM, but I have a bunch of different VMs where
I tests stuff, likely it was off when I ran the selftests.