slub: assign refcount for kmalloc_caches

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
printed.

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

Reported-by: Paul Hargrove <phhargrove@lbl.gov>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/slub.c b/mm/slub.c
index a0d698467f706bd617b960240cbb775cdc9cd034..321afab6a38d8f60819359646b7a56c5fff79e83 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3279,6 +3279,7 @@ static struct kmem_cache *__init create_kmalloc_cache(const char *name,
        if (kmem_cache_open(s, flags))
                goto panic;
 
+       s->refcount = 1;
        list_add(&s->list, &slab_caches);
        return s;