mm: memcontrol: add struct mem_cgroup_extension

hulk inclusion
category: bugfix
bugzilla: 47240
CVE: NA

-------------------------------------------------

Change struct mem_cgroup directly will causes the kabi broken.
So add a new struct mem_cgroup_extension for new variables.
Signed-off-by: NLiu Shixin <liushixin2@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

include/linux/memcontrol.h

@@ -318,6 +318,10 @@ struct mem_cgroup {
 	/* WARNING: nodeinfo must be the last member here */
 };
 
+struct mem_cgroup_extension {
+	struct mem_cgroup memcg;
+};
+
 /*
  * size of first charge trial. "32" comes from vmscan.c's magic value.
  * TODO: maybe necessary to use big numbers in big irons.

mm/memcontrol.c

@@ -4508,11 +4508,14 @@ static void free_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
 static void __mem_cgroup_free(struct mem_cgroup *memcg)
 {
 	int node;
+	struct mem_cgroup_extension *memcg_ext;
 
 	for_each_node(node)
 		free_mem_cgroup_per_node_info(memcg, node);
 	free_percpu(memcg->stat_cpu);
-	kfree(memcg);
+
+	memcg_ext = container_of(memcg, struct mem_cgroup_extension, memcg);
+	kfree(memcg_ext);
 }
 
 static void mem_cgroup_free(struct mem_cgroup *memcg)
@@ -4524,13 +4527,15 @@ static void mem_cgroup_free(struct mem_cgroup *memcg)
 static struct mem_cgroup *mem_cgroup_alloc(void)
 {
 	struct mem_cgroup *memcg;
+	struct mem_cgroup_extension *memcg_ext;
 	size_t size;
 	int node;
 
-	size = sizeof(struct mem_cgroup);
+	size = sizeof(struct mem_cgroup_extension);
 	size += nr_node_ids * sizeof(struct mem_cgroup_per_node *);
 
-	memcg = kzalloc(size, GFP_KERNEL);
+	memcg_ext = kzalloc(size, GFP_KERNEL);
+	memcg = &memcg_ext->memcg;
 	if (!memcg)
 		return NULL;