[PATCH] slab: add a check for the first kmem_cache not to be destroyed

[Kyunghwan Kwon]

The first kmem_cache created at booting up is supposed neither mergeable
nor destroyable but was possible to destroy. So prevent it.

Signed-off-by: Kyunghwan Kwon <kwon@xxxxxxxxxxxx>
---
 mm/slab_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 1dfc209..2d30ace 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -744,7 +744,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
 	bool need_rcu_barrier = false;
 	int err;
 
-	if (unlikely(!s))
+	if (unlikely(!s) || s->refcount == -1)
 		return;
 
 	get_online_cpus();
-- 
2.9.3 (Apple Git-75)