[PATCH 02/11] mm/slab: remove BAD_ALIEN_MAGIC again

From	js1304@gmail.com
Newsgroups	linux.kernel
Subject	[PATCH 02/11] mm/slab: remove BAD_ALIEN_MAGIC again
Date	2016-03-28 07:30 +0200
Message-ID	<rhxUv-2rs-23@gated-at.bofh.it> (permalink)
References	<rhxUt-2rs-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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From: Joonsoo Kim <iamjoonsoo.kim@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.kim@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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[PATCH 02/11] mm/slab: remove BAD_ALIEN_MAGIC again js1304@gmail.com - 2016-03-28 07:30 +0200
  Re: [PATCH 02/11] mm/slab: remove BAD_ALIEN_MAGIC again Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-28 11:00 +0200
    Re: [PATCH 02/11] mm/slab: remove BAD_ALIEN_MAGIC again Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-03-30 10:10 +0200
  Re: [PATCH 02/11] mm/slab: remove BAD_ALIEN_MAGIC again Andrew Morton <akpm@linux-foundation.org> - 2016-03-28 23:20 +0200
    Re: [PATCH 02/11] mm/slab: remove BAD_ALIEN_MAGIC again Christoph Lameter <cl@linux.com> - 2016-03-29 03:00 +0200

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