On Mon 28-08-17 18:27:05, Stephen Rothwell wrote:
> Hi Michal,
>
> On Mon, 28 Aug 2017 09:59:31 +0200 Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> >
> > From 31d551dbcb1b7987a4cd07767c1e2805849b7a26 Mon Sep 17 00:00:00 2001
> > From: Michal Hocko <mhocko@xxxxxxxx>
> > Date: Mon, 28 Aug 2017 09:41:39 +0200
> > Subject: [PATCH]
> > mm-hmm-struct-hmm-is-only-use-by-hmm-mirror-functionality-v2-fix
> >
> > Compiler is complaining for allnoconfig
> >
> > kernel/fork.c: In function 'mm_init':
> > kernel/fork.c:814:2: error: implicit declaration of function 'hmm_mm_init' [-Werror=implicit-function-declaration]
> > hmm_mm_init(mm);
> > ^
> > kernel/fork.c: In function '__mmdrop':
> > kernel/fork.c:893:2: error: implicit declaration of function 'hmm_mm_destroy' [-Werror=implicit-function-declaration]
> > hmm_mm_destroy(mm);
> >
> > Make sure that hmm_mm_init/hmm_mm_destroy empty stups are defined when
> > CONFIG_HMM is disabled.
> >
> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> > ---
> > include/linux/hmm.h | 7 +++----
> > 1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> > index 9583d9a15f9c..aeb94e682dda 100644
> > --- a/include/linux/hmm.h
> > +++ b/include/linux/hmm.h
> > @@ -508,11 +508,10 @@ static inline void hmm_mm_init(struct mm_struct *mm)
> > {
> > mm->hmm = NULL;
> > }
> > -#else /* IS_ENABLED(CONFIG_HMM_MIRROR) */
> > +#endif
> > +
> > +#else /* IS_ENABLED(CONFIG_HMM) */
> > static inline void hmm_mm_destroy(struct mm_struct *mm) {}
> > static inline void hmm_mm_init(struct mm_struct *mm) {}
> > -#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
> > -
> > -
> > #endif /* IS_ENABLED(CONFIG_HMM) */
> > #endif /* LINUX_HMM_H */
>
> What happens when CONFIG_HMM is defined but CONFIG_HMM_MIRROR is not?
> Or is that not possible (in which case why would we have
> CONFIG_HMM_MIRROR)?
This is something to Jerome to answer but hmm_mm_init/hmm_mm_destroy are
used regardless of the specific HMM configuration so an empty stub
should be defined unconditionally AFAIU.
--
Michal Hocko
SUSE Labs
