memcg: fix kabi broken when enable CONFIG_MEMCG_QOS

hulk inclusion
category: feature
bugzilla: 51827
CVE: NA

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

Fix it by moving memcg_priority from struct mem_cgroup to
struct mem_cgroup_extension.
Signed-off-by: NJing Xiangfeng <jingxiangfeng@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/linux/memcontrol.h

@@ -287,12 +287,6 @@ struct mem_cgroup {
 	bool			tcpmem_active;
 	int			tcpmem_pressure;
 
-#ifdef CONFIG_MEMCG_QOS
-	/* Currently support 0 and -1.
-	 * in the future it can expand to other value.
-	 */
-	int	memcg_priority;
-#endif
 #ifdef CONFIG_MEMCG_KMEM
         /* Index in the kmem_cache->memcg_params.memcg_caches array */
 	int kmemcg_id;
@@ -321,12 +315,21 @@ struct mem_cgroup {
 };
 
 struct mem_cgroup_extension {
+#ifdef CONFIG_MEMCG_QOS
+	/* Currently support 0 and -1.
+	 * in the future it can expand to other value.
+	 */
+	int	memcg_priority;
+#endif
 	spinlock_t split_queue_lock;
 	struct list_head split_queue;
 	unsigned long split_queue_len;
 	struct mem_cgroup memcg;
 };
 
+#define to_memcg_ext(cgroup)	\
+	container_of(cgroup, struct mem_cgroup_extension, memcg)
+
 #ifdef CONFIG_MEMCG_QOS
 bool memcg_low_priority_scan_tasks(int (*)(struct task_struct *, void *),
 				   void *);

mm/memcontrol.c

@@ -3407,29 +3407,42 @@ static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
 static void memcg_qos_init(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup *parent = parent_mem_cgroup(memcg);
+	struct mem_cgroup_extension *memcg_ext;
+	struct mem_cgroup_extension *parent_ext;
 
 	if (!parent)
 		return;
 
-	if (parent->memcg_priority && parent->use_hierarchy)
-		memcg->memcg_priority = parent->memcg_priority;
+	memcg_ext = to_memcg_ext(memcg);
+	parent_ext = to_memcg_ext(parent);
+
+	if (parent_ext->memcg_priority && parent->use_hierarchy)
+		memcg_ext->memcg_priority = parent_ext->memcg_priority;
 }
 
 static s64 memcg_qos_read(struct cgroup_subsys_state *css,
 				      struct cftype *cft)
 {
-	return mem_cgroup_from_css(css)->memcg_priority;
+	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
+	struct mem_cgroup_extension *memcg_ext;
+
+	memcg_ext = to_memcg_ext(memcg);
+
+	return memcg_ext->memcg_priority;
 }
 
 static int memcg_qos_write(struct cgroup_subsys_state *css,
 				       struct cftype *cft, s64 val)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
+	struct mem_cgroup_extension *memcg_ext;
+
+	memcg_ext = to_memcg_ext(memcg);
 
 	if (val >= 0)
-		memcg->memcg_priority = 0;
+		memcg_ext->memcg_priority = 0;
 	else
-		memcg->memcg_priority = -1;
+		memcg_ext->memcg_priority = -1;
 
 	return 0;
 }
@@ -3438,13 +3451,15 @@ static struct mem_cgroup *memcg_find_max_usage(struct mem_cgroup *last)
 {
 	struct mem_cgroup *iter, *max_memcg = NULL;
 	struct cgroup_subsys_state *css;
+	struct mem_cgroup_extension *memcg_ext;
 	unsigned long usage, max_usage = 0;
 
 	rcu_read_lock();
 	css_for_each_descendant_pre(css, &root_mem_cgroup->css) {
 		iter = mem_cgroup_from_css(css);
+		memcg_ext = to_memcg_ext(iter);
 
-		if (!iter->memcg_priority || iter == root_mem_cgroup ||
+		if (!memcg_ext->memcg_priority || iter == root_mem_cgroup ||
 			iter == last)
 			continue;
 
@@ -3504,12 +3519,13 @@ bool memcg_low_priority_scan_tasks(int (*fn)(struct task_struct *, void *),
 void memcg_print_bad_task(void *arg, int ret)
 {
 	struct oom_control *oc = arg;
-
-	if (!ret && oc->chosen) {
 	struct mem_cgroup *memcg;
+	struct mem_cgroup_extension *memcg_ext;
 
+	if (!ret && oc->chosen) {
 		memcg = mem_cgroup_from_task(oc->chosen);
-		if (memcg->memcg_priority)
+		memcg_ext = to_memcg_ext(memcg);
+		if (memcg_ext->memcg_priority)
 			pr_info("The bad task [%d:%s] is from low-priority memcg.\n",
 				oc->chosen->pid, oc->chosen->comm);
 	}

mm/oom_kill.c

@@ -327,6 +327,8 @@ static bool oom_next_task(struct task_struct *task, struct oom_control *oc,
 {
 	struct mem_cgroup *cur_memcg;
 	struct mem_cgroup *oc_memcg;
+	struct mem_cgroup_extension *cur_ext;
+	struct mem_cgroup_extension *oc_ext;
 
 
 	if (!points)
@@ -337,14 +339,16 @@ static bool oom_next_task(struct task_struct *task, struct oom_control *oc,
 
 	oc_memcg = mem_cgroup_from_task(oc->chosen);
 	cur_memcg = mem_cgroup_from_task(task);
+	oc_ext = to_memcg_ext(oc_memcg);
+	cur_ext = to_memcg_ext(cur_memcg);
 
-	if (cur_memcg->memcg_priority == oc_memcg->memcg_priority) {
+	if (cur_ext->memcg_priority == oc_ext->memcg_priority) {
 		if (points < oc->chosen_points)
 			return true;
 		return false;
 	}
 	/* if oc is low-priority, so skip the task */
-	if (oc_memcg->memcg_priority)
+	if (oc_ext->memcg_priority)
 		return true;
 
 	return false;