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From:   Yuanchu Xie <yuanchu@google.com>
Date:   Tue, 24 May 2022 17:55:11 -0700
Message-ID: <CAJj2-QGUsqx8uRTamv7Hbw_-FRJOtrEnX6=fGEseZDJEtcnOaw@mail.gmail.com>
Subject: Re: [PATCH v3] selftests/damon: suppress compiler warnings for huge_count_read_write
To:     Shuah Khan <shuah@kernel.org>
Cc:     SeongJae Park <sj@kernel.org>, Markus Boehme <markubo@amazon.de>,
        David Rientjes <rientjes@google.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
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Hi Shuah,

On Wed, May 4, 2022 at 11:45 AM SeongJae Park <sj@kernel.org> wrote:
>
> Hi Yuanchu,
>
> On Wed, 4 May 2022 18:29:08 +0000 Yuanchu Xie <yuanchu@google.com> wrote:
>
> > The test case added in commit db7a347b26fe ("mm/damon/dbgfs:
> > use '__GFP_NOWARN' for user-specified size buffer allocation")
> > intentionally writes and reads with a large count to cause
> > allocation failure and check for kernel warnings. We suppress
> > the compiler warnings for these calls as they work as intended.
> >
> > Signed-off-by: Yuanchu Xie <yuanchu@google.com>
> > ---
>
> It would be a good practice to mention the changes from the previous vers=
ion of
> this patch here[1].
>
> [1] https://docs.kernel.org/process/submitting-patches.html#the-canonical=
-patch-format
>
> >  tools/testing/selftests/damon/huge_count_read_write.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/tools/testing/selftests/damon/huge_count_read_write.c b/to=
ols/testing/selftests/damon/huge_count_read_write.c
> > index ad7a6b4cf338..91bd80c75cd9 100644
> > --- a/tools/testing/selftests/damon/huge_count_read_write.c
> > +++ b/tools/testing/selftests/damon/huge_count_read_write.c
> > @@ -2,6 +2,8 @@
> >  /*
> >   * Author: SeongJae Park <sj@kernel.org>
> >   */
> > +#pragma GCC diagnostic ignored "-Wstringop-overflow"
> > +#pragma GCC diagnostic ignored "-Wstringop-overread"
>
> I agree that this must be the cleaner way than v2.  But, I get below warn=
ing
> after applying this:
>
>     $ sudo make -C tools/testing/selftests/damon run_tests
>     make: Entering directory '/home/sjpark/linux/tools/testing/selftests/=
damon'
>     gcc     huge_count_read_write.c  -o /home/sjpark/linux/tools/testing/=
selftests/damon/huge_count_read_write
>     huge_count_read_write.c:6:32: warning: unknown option after =E2=80=98=
#pragma GCC diagnostic=E2=80=99 kind [-Wpragmas]
>         6 | #pragma GCC diagnostic ignored "-Wstringop-overread"
>           |                                ^~~~~~~~~~~~~~~~~~~~~
>
> My gcc version is:
>
>     $ gcc --version
>     gcc (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0

    $ gcc --version
    gcc (Debian 11.2.0-16+build1) 11.2.0

I believe this is a new warning for gcc-11 [1], and somewhat unfortunate th=
at
it results in a warning for gcc-9.4. So a patch that would resolve the test
warnings for gcc 11 would introduce a new warning for gcc 9, and vice versa=
.
What's the preferred solution here?

[1] https://gcc.gnu.org/onlinedocs/gcc-10.3.0/gcc/Warning-Options.html

Thanks,
Yuanchu