On 4 August 2013 13:39, Michal Hocko <mhocko@suse.cz> wrote:

> On Sun 04-08-13 10:41:01, Manjunath Goudar wrote:
> > s patch adds a Kconfig dependency on an MMU being available before
> > CMA can be enabled.  Without this patch, CMA can be enabled on an
> > MMU-less system which can lead to issues. This was discovered during
> > randconfig testing, in which CMA was enabled w/o MMU being enabled,
> > leading to the following error:
> >
> >  CC      mm/migrate.o
> > mm/migrate.c: In function ‘remove_migration_pte’:
> > mm/migrate.c:134:3: error: implicit declaration of function
> ‘pmd_trans_huge’
> > [-Werror=implicit-function-declaration]
> >    if (pmd_trans_huge(*pmd))
> >    ^
> > mm/migrate.c:137:3: error: implicit declaration of function
> ‘pte_offset_map’
> > [-Werror=implicit-function-declaration]
> >    ptep = pte_offset_map(pmd, addr);
>
> This is a migration code but you are updating configuration for CMA
> which doesn't make much sense to me.
> I guess you wanted to disable migration for CMA instead?
>

 Yes you are right.Already Chen Gang has written similar patch.

>
> > Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
> > Acked-by: Arnd Bergmann <arnd@linaro.org>
> > Cc: Deepak Saxena <dsaxena@linaro.org>
> > Cc: IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
> > Cc: Hirokazu Takahashi <taka@valinux.co.jp>
> > Cc: Dave Hansen <haveblue@us.ibm.com>
> > Cc: linux-mm@kvack.org
> > Cc: Johannes Weiner <hannes@cmpxchg.org>
> > Cc: Michal Hocko <mhocko@suse.cz>
> > Cc: Balbir Singh <bsingharora@gmail.com>
> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  mm/Kconfig |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/Kconfig b/mm/Kconfig
> > index 256bfd0..ad6b98e 100644
> > --- a/mm/Kconfig
> > +++ b/mm/Kconfig
> > @@ -522,7 +522,7 @@ config MEM_SOFT_DIRTY
> >
> >  config CMA
> >       bool "Contiguous Memory Allocator"
> > -     depends on HAVE_MEMBLOCK
> > +     depends on MMU && HAVE_MEMBLOCK
> >       select MIGRATION
> >       select MEMORY_ISOLATION
> >       help
> > --
> > 1.7.9.5
> >
> > --
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> > see: http://www.linux-mm.org/ .
> > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>
> --
> Michal Hocko
> SUSE Labs
>

Thanks
Manjunath Goudar