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Date:   Tue, 10 Nov 2020 11:50:37 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Souptick Joarder <jrdr.linux@gmail.com>
Cc:     Alex Shi <alex.shi@linux.alibaba.com>,
        Linux-MM <linux-mm@kvack.org>, linux-kernel@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Josef Bacik <josef@toxicpanda.com>
Subject: Re: [PATCH] mm/filemap: add static for function
 __add_to_page_cache_locked
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On Tue, 10 Nov 2020 08:39:24 +0530 Souptick Joarder <jrdr.linux@gmail.com> wrote:

> On Fri, Nov 6, 2020 at 4:55 PM Alex Shi <alex.shi@linux.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.

> >
> > Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: linux-mm@kvack.org
> > Cc: linux-kernel@vger.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##__))

Alexei, can you please comment?