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?

> 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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--
Michal Hocko
SUSE Labs