From: Andrey Vagin <avagin@openvz.org>
Date: Wed, 11 Sep 2013 21:22:18 +0000 (-0700)
Subject: kmemcg: don't allocate extra memory for root memcg_cache_params
X-Git-Tag: v3.12-rc1~52^2~198
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=90c7a79cc45becc6cdb8c026d55ace19e299a02d;hp=e76b63f80d938a1319eb5fb0ae7ea69bddfbae38;p=linux-2.6-block.git

kmemcg: don't allocate extra memory for root memcg_cache_params

The memcg_cache_params structure contains the common part and the union,
which represents two different types of data: one for root cashes and
another for child caches.

The size of child data is fixed.  The size of the memcg_caches array is
calculated in runtime.

Currently the size of memcg_cache_params for root caches is calculated
incorrectly, because it includes the size of parameters for child caches.

ssize_t size = memcg_caches_array_size(num_groups);
size *= sizeof(void *);

size += sizeof(struct memcg_cache_params);

v2: Fix a typo in calculations

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3b83957b6439..5ca1dcf77ce9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3121,7 +3121,7 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
 		ssize_t size = memcg_caches_array_size(num_groups);
 
 		size *= sizeof(void *);
-		size += sizeof(struct memcg_cache_params);
+		size += offsetof(struct memcg_cache_params, memcg_caches);
 
 		s->memcg_params = kzalloc(size, GFP_KERNEL);
 		if (!s->memcg_params) {
@@ -3164,13 +3164,16 @@ int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
 int memcg_register_cache(struct mem_cgroup *memcg, struct kmem_cache *s,
 			 struct kmem_cache *root_cache)
 {
-	size_t size = sizeof(struct memcg_cache_params);
+	size_t size;
 
 	if (!memcg_kmem_enabled())
 		return 0;
 
-	if (!memcg)
+	if (!memcg) {
+		size = offsetof(struct memcg_cache_params, memcg_caches);
 		size += memcg_limited_groups_array_size * sizeof(void *);
+	} else
+		size = sizeof(struct memcg_cache_params);
 
 	s->memcg_params = kzalloc(size, GFP_KERNEL);
 	if (!s->memcg_params)