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Subject[ 89/89] slub: assign refcount for kmalloc_caches
3.7-stable review patch.  If anyone has any objections, please let me know.


From: CAI Qian <>

This is for stable-3.7.y only and this problem has already been solved
in mainline through some slab/slub re-work which isn't suitable to
backport here. See create_kmalloc_cache() in mm/slab_common.c there.

commit cce89f4f6911286500cf7be0363f46c9b0a12ce0('Move kmem_cache
refcounting to common code') moves some refcount manipulation code to
common code. Unfortunately, it also removed refcount assignment for
kmalloc_caches. So, kmalloc_caches's refcount is initially 0.
This makes erroneous situation.

Paul Hargrove report that when he create a 8-byte kmem_cache and
destory it, he encounter below message.
'Objects remaining in kmalloc-8 on kmem_cache_close()'

8-byte kmem_cache merge with 8-byte kmalloc cache and refcount is
increased by one. So, resulting refcount is 1. When destroy it, it hit
refcount = 0, then kmem_cache_close() is executed and error message is

This patch assign initial refcount 1 to kmalloc_caches, so fix this
erroneous situation.

Reported-by: Paul Hargrove <>
Cc: Christoph Lameter <>
Signed-off-by: Joonsoo Kim <>
Signed-off-by: CAI Qian <>
Signed-off-by: Greg Kroah-Hartman <>

mm/slub.c | 1 +
1 file changed, 1 insertion(+)

--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3279,6 +3279,7 @@ static struct kmem_cache *__init create_
if (kmem_cache_open(s, flags))
goto panic;

+ s->refcount = 1;
list_add(&s->list, &slab_caches);
return s;

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