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

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Message-ID: <4a1f9359-8ecb-4962-92f5-a52cf2fd8564@redhat.com>
Date: Wed, 13 Mar 2024 23:29:35 +0100
From: David Hildenbrand <david@...hat.com>
To: Peter Xu <peterx@...hat.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 Muhammad Usama Anjum <usama.anjum@...labora.com>
Subject: Re: [PATCH] mm/memory: Fix missing pte marker for !page on pte zaps

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@...hat.com wrote:
>>> From: Peter Xu <peterx@...hat.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.

-- 
Cheers,

David / dhildenb