linux-kernel - Re: [PATCH] mm/filemap: add static for function __add_to_page_cache

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Message-ID: <CAFxkdApgQ4RCt-J43cK4_128pXr=Xn5jw+q0kOaP-TYufk_tPA@mail.gmail.com>
Date:   Mon, 7 Dec 2020 12:35:49 -0600
From:   Justin Forbes <jmforbes@...uxtx.org>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     Alex Shi <alex.shi@...ux.alibaba.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Josef Bacik <josef@...icpanda.com>
Subject: Re: [PATCH] mm/filemap: add static for function __add_to_page_cache_locked

On Mon, Dec 7, 2020 at 2:16 AM Michal Kubecek <mkubecek@...e.cz> wrote:
>
> On Thu, Nov 12, 2020 at 08:18:57AM +0800, Alex Shi wrote:
> >
> >
> > 在 2020/11/11 上午3:50, Andrew Morton 写道:
> > > On Tue, 10 Nov 2020 08:39:24 +0530 Souptick Joarder <jrdr.linux@...il.com> wrote:
> > >
> > >> On Fri, Nov 6, 2020 at 4:55 PM Alex Shi <alex.shi@...ux.alibaba.com> wrote:
> > >>>
> > >>> Otherwise it cause gcc warning:
> > >>>           ^~~~~~~~~~~~~~~
> > >>> ../mm/filemap.c:830:14: warning: no previous prototype for
> > >>> ‘__add_to_page_cache_locked’ [-Wmissing-prototypes]
> > >>>  noinline int __add_to_page_cache_locked(struct page *page,
> > >>>               ^~~~~~~~~~~~~~~~~~~~~~~~~~
> > >>
> > >> Is CONFIG_DEBUG_INFO_BTF enabled in your .config ?
> > >
> > > hm, yes.
> >
> > When the config enabled, compiling looks good untill pahole tool
> > used to get BTF info, but I still failed on a right version pahole
> > > 1.16. Sorry.
> >
> > >
> > >>>
> > >>> Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
> > >>> Cc: Andrew Morton <akpm@...ux-foundation.org>
> > >>> Cc: linux-mm@...ck.org
> > >>> Cc: linux-kernel@...r.kernel.org
> > >>> ---
> > >>>  mm/filemap.c | 2 +-
> > >>>  1 file changed, 1 insertion(+), 1 deletion(-)
> > >>>
> > >>> diff --git a/mm/filemap.c b/mm/filemap.c
> > >>> index d90614f501da..249cf489f5df 100644
> > >>> --- a/mm/filemap.c
> > >>> +++ b/mm/filemap.c
> > >>> @@ -827,7 +827,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
> > >>>  }
> > >>>  EXPORT_SYMBOL_GPL(replace_page_cache_page);
> > >>>
> > >>> -noinline int __add_to_page_cache_locked(struct page *page,
> > >>> +static noinline int __add_to_page_cache_locked(struct page *page,
> > >>>                                         struct address_space *mapping,
> > >>>                                         pgoff_t offset, gfp_t gfp,
> > >>>                                         void **shadowp)
> > >
> > > It's unclear to me whether BTF_ID() requires that the target symbol be
> > > non-static.  It doesn't actually reference the symbol:
> > >
> > > #define BTF_ID(prefix, name) \
> > >         __BTF_ID(__ID(__BTF_ID__##prefix##__##name##__))
> > >
> >
> > The above usage make me thought BTF don't require the symbol, though
> > the symbol still exist in vmlinux with 'static'.
> >
> > So any comments of this, Alexei?
>
> It's probably more complicated: our v5.10-rc7 builds with
> CONFIG_DEBUG_INFO_BTF=y fail on ppc64 and ppc64le with
>
>      BTFIDS  vmlinux
>    FAILED unresolved symbol __add_to_page_cache_locked
>
>
> but succeed on x86_64, i586, aarch64 and s390x. So far I don't see why
> this should depend on architecture.
>
Fedora is failing with rc7 on the same issue on PPC only.

Justin