mm: memcg: gather memcg1-specific fields initialization in memcg1_memcg_init()

Gather all memcg1-specific struct mem_cgroup's members initialization in a
new memcg1_memcg_init() function, defined in mm/memcontrol-v1.c. 
Obviously, if CONFIG_MEMCG_V1 is not set, there is no need to initialize
these fields, so the function becomes trivial.

Link: https://lkml.kernel.org/r/20240628210317.272856-5-roman.gushchin@linux.devSigned-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcontrol-v1.c

@@ -1961,6 +1961,15 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
 	return ret;
 }
 
+void memcg1_memcg_init(struct mem_cgroup *memcg)
+{
+	INIT_LIST_HEAD(&memcg->oom_notify);
+	mutex_init(&memcg->thresholds_lock);
+	spin_lock_init(&memcg->move_lock);
+	INIT_LIST_HEAD(&memcg->event_list);
+	spin_lock_init(&memcg->event_list_lock);
+}
+
 void memcg1_css_offline(struct mem_cgroup *memcg)
 {
 	struct mem_cgroup_event *event, *tmp;

mm/memcontrol-v1.h

@@ -71,6 +71,7 @@ int memory_stat_show(struct seq_file *m, void *v);
 
 /* Cgroup v1-specific declarations */
 #ifdef CONFIG_MEMCG_V1
+void memcg1_memcg_init(struct mem_cgroup *memcg);
 void memcg1_remove_from_trees(struct mem_cgroup *memcg);
 
 static inline void memcg1_soft_limit_reset(struct mem_cgroup *memcg)
@@ -119,6 +120,7 @@ extern struct cftype mem_cgroup_legacy_files[];
 
 #else	/* CONFIG_MEMCG_V1 */
 
+static inline void memcg1_memcg_init(struct mem_cgroup *memcg) {}
 static inline void memcg1_remove_from_trees(struct mem_cgroup *memcg) {}
 static inline void memcg1_soft_limit_reset(struct mem_cgroup *memcg) {}
 static inline bool memcg1_wait_acct_move(struct mem_cgroup *memcg) { return false; }

mm/memcontrol.c

@@ -3589,13 +3589,9 @@ static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent)
 		goto fail;
 
 	INIT_WORK(&memcg->high_work, high_work_func);
-	INIT_LIST_HEAD(&memcg->oom_notify);
-	mutex_init(&memcg->thresholds_lock);
-	spin_lock_init(&memcg->move_lock);
 	vmpressure_init(&memcg->vmpressure);
-	INIT_LIST_HEAD(&memcg->event_list);
-	spin_lock_init(&memcg->event_list_lock);
 	memcg->socket_pressure = jiffies;
+	memcg1_memcg_init(memcg);
 #ifdef CONFIG_MEMCG_KMEM
 	memcg->kmemcg_id = -1;
 	INIT_LIST_HEAD(&memcg->objcg_list);