linux-kernel - Re: Re: [PATCH v18 01/14] mm/page_ext: Export lookup_page

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Date:   Mon, 13 Jul 2020 20:19:09 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     SeongJae Park <sjpark@...zon.com>
Cc:     akpm@...ux-foundation.org, SeongJae Park <sjpark@...zon.de>,
        Jonathan.Cameron@...wei.com, aarcange@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, amit@...nel.org,
        benh@...nel.crashing.org, brendan.d.gregg@...il.com,
        brendanhiggins@...gle.com, cai@....pw, colin.king@...onical.com,
        corbet@....net, david@...hat.com, dwmw@...zon.com,
        foersleo@...zon.de, irogers@...gle.com, jolsa@...hat.com,
        kirill@...temov.name, mark.rutland@....com, mgorman@...e.de,
        minchan@...nel.org, mingo@...hat.com, namhyung@...nel.org,
        peterz@...radead.org, rdunlap@...radead.org, riel@...riel.com,
        rientjes@...gle.com, rostedt@...dmis.org, sblbir@...zon.com,
        shakeelb@...gle.com, shuah@...nel.org, sj38.park@...il.com,
        snu@...zon.de, vbabka@...e.cz, vdavydov.dev@...il.com,
        yang.shi@...ux.alibaba.com, ying.huang@...el.com,
        linux-damon@...zon.com, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH v18 01/14] mm/page_ext: Export lookup_page_ext() to
 GPL modules

On Mon, Jul 13, 2020 at 02:21:43PM +0200, SeongJae Park wrote:
> On Mon, 13 Jul 2020 15:08:42 +0300 Mike Rapoport <rppt@...nel.org> wrote:
> 
> > Hi,
> > 
> > On Mon, Jul 13, 2020 at 10:41:31AM +0200, SeongJae Park wrote:
> > > From: SeongJae Park <sjpark@...zon.de>
> > > 
> > > This commit exports 'lookup_page_ext()' to GPL modules.  It will be used
> > > by DAMON in following commit for the implementation of the region based
> > > sampling.
> > 
> > Maybe I'm missing something, but why is DAMON a module?
> 
> I made it loadable just for easier adoption from downstream kernels.  I could
> drop the module build support if asked.
 
Well, exporting core mm symbols to modules should be considred very
carefully. 

Why lookup_page_ext() is required for DAMON? It is not used anywhere in
this patchset.


> Thanks,
> SeongJae Park
> 
> > 
> > > Signed-off-by: SeongJae Park <sjpark@...zon.de>
> > > Reviewed-by: Leonard Foerster <foersleo@...zon.de>
> > > Reviewed-by: Varad Gautam <vrd@...zon.de>
> > > ---
> > >  mm/page_ext.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/mm/page_ext.c b/mm/page_ext.c
> > > index a3616f7a0e9e..9d802d01fcb5 100644
> > > --- a/mm/page_ext.c
> > > +++ b/mm/page_ext.c
> > > @@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
> > >  					MAX_ORDER_NR_PAGES);
> > >  	return get_entry(base, index);
> > >  }
> > > +EXPORT_SYMBOL_GPL(lookup_page_ext);
> > >  
> > >  static int __init alloc_node_page_ext(int nid)
> > >  {
> > > -- 
> > > 2.17.1
> > > 
> > 
> > -- 
> > Sincerely yours,
> > Mike.

-- 
Sincerely yours,
Mike.