[PATCH] MM: Make Contiguous Memory Allocator depends on MMU

[Manjunath Goudar]

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);

Signed-off-by: Manjunath Goudar <manjunath.goudar at linaro.org>
Acked-by: Arnd Bergmann <arnd at linaro.org>
Cc: Deepak Saxena <dsaxena at linaro.org>
Cc: IWAMOTO Toshihiro <iwamoto at valinux.co.jp>
Cc: Hirokazu Takahashi <taka at valinux.co.jp>
Cc: Dave Hansen <haveblue at us.ibm.com>
Cc: linux-mm at kvack.org
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: Michal Hocko <mhocko at suse.cz>
Cc: Balbir Singh <bsingharora at gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu at 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