mm/slab_common.c: mark kmalloc machinery as __ro_after_init

kmalloc caches aren't relocated after being set up neither does
"size_index" array.

Link: http://lkml.kernel.org/r/20180226203519.GA6886@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab_common.c

@@ -10,6 +10,7 @@
 #include <linux/poison.h>
 #include <linux/interrupt.h>
 #include <linux/memory.h>
+#include <linux/cache.h>
 #include <linux/compiler.h>
 #include <linux/module.h>
 #include <linux/cpu.h>
@@ -954,11 +955,11 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name, size_t size,
 	return s;
 }
 
-struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1];
+struct kmem_cache *kmalloc_caches[KMALLOC_SHIFT_HIGH + 1] __ro_after_init;
 EXPORT_SYMBOL(kmalloc_caches);
 
 #ifdef CONFIG_ZONE_DMA
-struct kmem_cache *kmalloc_dma_caches[KMALLOC_SHIFT_HIGH + 1];
+struct kmem_cache *kmalloc_dma_caches[KMALLOC_SHIFT_HIGH + 1] __ro_after_init;
 EXPORT_SYMBOL(kmalloc_dma_caches);
 #endif
 
@@ -968,7 +969,7 @@ EXPORT_SYMBOL(kmalloc_dma_caches);
  * of two cache sizes there. The size of larger slabs can be determined using
  * fls.
  */
-static s8 size_index[24] = {
+static s8 size_index[24] __ro_after_init = {
 	3,	/* 8 */
 	4,	/* 16 */
 	5,	/* 24 */