From: Joonsoo Kim <iamjoonsoo....@lge.com>

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....@lge.com>
---
 mm/slab.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 043606a..a5a205b 100644
--- 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)
@@ -637,7 +635,7 @@ 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)
@@ -1205,7 +1203,7 @@ 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++)
-- 
1.9.1

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