[PATCH] mm: silence -Woverride-init/initializer-overrides

[Qian Cai <cai@lca.pw>]

When compiling a kernel with W=1, there are several of those warnings
due to arm64 override a field by purpose. Just disable those warnings
for both GCC and Clang of this file, so it will help dig "gems" hidden
in the W=1 warnings by reducing some noises.

mm/init-mm.c:39:2: warning: initializer overrides prior initialization
of this subobject [-Winitializer-overrides]
        INIT_MM_CONTEXT(init_mm)
        ^~~~~~~~~~~~~~~~~~~~~~~~
./arch/arm64/include/asm/mmu.h:133:9: note: expanded from macro
'INIT_MM_CONTEXT'
        .pgd = init_pg_dir,
               ^~~~~~~~~~~
mm/init-mm.c:30:10: note: previous initialization is here
        .pgd            = swapper_pg_dir,
                          ^~~~~~~~~~~~~~

Note: there is a side project trying to support explicitly allowing
specific initializer overrides in Clang, but there is no guarantee it
will happen or not.

https://github.com/ClangBuiltLinux/linux/issues/639

Signed-off-by: Qian Cai <cai@lca.pw>
---
 mm/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/Makefile b/mm/Makefile
index d0b295c3b764..5a30b8ecdc55 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -21,6 +21,9 @@ KCOV_INSTRUMENT_memcontrol.o := n
 KCOV_INSTRUMENT_mmzone.o := n
 KCOV_INSTRUMENT_vmstat.o := n
 
+CFLAGS_init-mm.o += $(call cc-disable-warning, override-init)
+CFLAGS_init-mm.o += $(call cc-disable-warning, initializer-overrides)
+
 mmu-y			:= nommu.o
 mmu-$(CONFIG_MMU)	:= highmem.o memory.o mincore.o \
 			   mlock.o mmap.o mmu_gather.o mprotect.o mremap.o \
-- 
1.8.3.1