Subject: Re: linux-next: build failure after merge of the akpm tree

From: Mike Rapoport <[email-masked]>
Date: Sun, 15 Nov 2020 11:01:05 +0200

On Fri, Nov 13, 2020 at 05:14:52PM -0800, Andrew Morton wrote:
> On Fri, 13 Nov 2020 18:02:39 +1100 Stephen Rothwell <[email-masked]> wrote:
> 
> > Hi all,
> > 
> > After merging the akpm tree, today's linux-next build (i386 defconfig)
> > failed like this:
> > 
> > mm/secretmem.c: In function 'secretmem_memcg_charge':
> > mm/secretmem.c:72:4: error: 'struct page' has no member named 'memcg_data'
> >    72 |   p->memcg_data = page->memcg_data;
> >       |    ^~
> > mm/secretmem.c:72:23: error: 'struct page' has no member named 'memcg_data'
> >    72 |   p->memcg_data = page->memcg_data;
> >       |                       ^~
> > mm/secretmem.c: In function 'secretmem_memcg_uncharge':
> > mm/secretmem.c:86:4: error: 'struct page' has no member named 'memcg_data'
> >    86 |   p->memcg_data = 0;
> >       |    ^~
> > 
> > ...
> >
> > --- a/mm/secretmem.c
> > +++ b/mm/secretmem.c
> > @@ -69,7 +69,9 @@ static int secretmem_memcg_charge(struct page *page, gfp_t gfp, int order)
> >  	for (i = 1; i < nr_pages; i++) {
> >  		struct page *p = page + i;
> >  
> > +#ifdef CONFIG_MEMCG
> >  		p->memcg_data = page->memcg_data;
> > +#endif
> >  	}
> >  
> >  	return 0;
> 
> Thanks, that'll work for now.
> 
> I guess we're looking at adding a set_page_memcg() (I'd prefer
> page_memcg_set()).
> 
> But probably these functions shouldn't be compiled at all if
> CONFIG_MEMCG=n.

My preference would be to put the entire function body in '#ifdef
CONFIG_MEMCG' here.

-- 
Sincerely yours,
Mike.