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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Wed, 26 May 2021 11:41:41 -0700
Message-ID: <CAEf4BzbbQfwUERObV4EQ4fTx3auKZm_CyoidWK7hWAK32wFZ3A@mail.gmail.com>
Subject: Re: [PATCH] mm/page_alloc: Work around a pahole limitation with
 zero-sized struct pagesets
To:     Mel Gorman <mgorman@techsingularity.net>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Suchanek <msuchanek@suse.de>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Hritik Vijay <hritikxx8@gmail.com>, bpf <bpf@vger.kernel.org>,
        Linux-Net <netdev@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>
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On Wed, May 26, 2021 at 11:13 AM Mel Gorman <mgorman@techsingularity.net> wrote:
>
> On Wed, May 26, 2021 at 09:57:31AM -0700, Andrii Nakryiko wrote:
> > > This patch checks for older versions of pahole and forces struct pagesets
> > > to be non-zero sized as a workaround when CONFIG_DEBUG_INFO_BTF is set. A
> > > warning is omitted so that distributions can update pahole when 1.22
> >
> > s/omitted/emitted/ ?
> >
>
> Yes.
>
> > > is released.
> > >
> > > Reported-by: Michal Suchanek <msuchanek@suse.de>
> > > Reported-by: Hritik Vijay <hritikxx8@gmail.com>
> > > Debugged-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> > > ---
> >
> > Looks good! I verified that this does fix the issue on the latest
> > linux-next tree, thanks!
> >
>
> Excellent
>
> > One question, should
> >
> > Fixes: 5716a627517d ("mm/page_alloc: convert per-cpu list protection
> > to local_lock")
> >
> > be added to facilitate backporting?
> >
>
> The git commit is not stable because the patch "mm/page_alloc: convert
> per-cpu list protection to local_lock" is in Andrew's mmotm tree which is

Oh, I didn't know about this instability.

> quilt based. I decided not to treat the patch as a fix because the patch is
> not wrong as such, it's a limitation of an external tool.  However, I would
> expect both the problematic patch and the BTF workaround to go in during
> the same merge window so backports to -stable should not be required.

Yep, makes sense.

>
> > Either way:
> >
> > Acked-by: Andrii Nakryiko <andrii@kernel.org>
> > Tested-by: Andrii Nakryiko <andrii@kernel.org>
> >
>
> Thanks!
>
> --
> Mel Gorman
> SUSE Labs