linux-kernel - Re: [PATCH 11/29] selftests/mm: Drop test_uffdio_zeropage

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Date:   Mon, 3 Apr 2023 12:16:01 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Leonardo Bras Soares Passos <lsoaresp@...hat.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Nadav Amit <nadav.amit@...il.com>
Subject: Re: [PATCH 11/29] selftests/mm: Drop test_uffdio_zeropage_eexist

On Fri, Mar 31, 2023 at 05:03:17PM -0700, Mike Kravetz wrote:
> On 03/30/23 12:07, Peter Xu wrote:
> > The idea was trying to flip this var in the alarm handler from time to time
> > to test -EEXIST of UFFDIO_ZEROPAGE, but firstly it's only used in the
> > zeropage test so probably only used once, meanwhile we passed
> > "retry==false" so it'll never got tested anyway.
> > 
> > Drop both sides so we always test UFFDIO_ZEROPAGE retries if has_zeropage
> > is set (!hugetlb).
> > 
> > One more thing to do is doing UFFDIO_REGISTER for the alias buffer too,
> > because otherwise the test won't even pass!  We were just lucky that this
> > test never really got ran at all.
> > 
> > Signed-off-by: Peter Xu <peterx@...hat.com>
> > ---
> >  tools/testing/selftests/mm/userfaultfd.c | 20 +++++++++++---------
> >  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> Thanks!  With only passing "retry==false", that code is indeed dead.  I had
> to read the code again to understand area_dst_alias.  Thanks for taking this
> on as the code is difficult to understand.

Yes it's very confusing.  I plan to move on the cleanup to remove all these
global variables at least in the unit tests, but I'll first see how this
one goes.

> 
> Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>

Thanks,

-- 
Peter Xu