mm/slab: remove BAD_ALIEN_MAGIC again

Initial attemp to remove BAD_ALIEN_MAGIC is once reverted by 'commit
edcad2509550 ("Revert "slab: remove BAD_ALIEN_MAGIC"")' because it
causes a problem on m68k which has many node but !CONFIG_NUMA.  In this
case, although alien cache isn't used at all but to cope with some
initialization path, garbage value is used and that is BAD_ALIEN_MAGIC.
Now, this patch set use_alien_caches to 0 when !CONFIG_NUMA, there is no
initialization path problem so we don't need BAD_ALIEN_MAGIC at all.  So
remove it.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/slab.c b/mm/slab.c
index 3f1cc1ca4d88f577e9aae695f35db728590272be..f36d3493f49f2a50b8e1315fe2a9475e5ef237c7 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -421,8 +421,6 @@ static struct kmem_cache kmem_cache_boot = {
        .name = "kmem_cache",
 };
 
-#define BAD_ALIEN_MAGIC 0x01020304ul
-
 static DEFINE_PER_CPU(struct delayed_work, slab_reap_work);
 
 static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
@@ -644,7 +642,7 @@ static int transfer_objects(struct array_cache *to,
 static inline struct alien_cache **alloc_alien_cache(int node,
                                                int limit, gfp_t gfp)
 {
-       return (struct alien_cache **)BAD_ALIEN_MAGIC;
+       return NULL;
 }
 
 static inline void free_alien_cache(struct alien_cache **ac_ptr)
@@ -1212,7 +1210,7 @@ void __init kmem_cache_init(void)
                                        sizeof(struct rcu_head));
        kmem_cache = &kmem_cache_boot;
 
-       if (num_possible_nodes() == 1)
+       if (!IS_ENABLED(CONFIG_NUMA) || num_possible_nodes() == 1)
                use_alien_caches = 0;
 
        for (i = 0; i < NUM_INIT_LISTS; i++)