cgroup: get rid of populate for memcg

The last man standing justifying the need for populate() is the
sock memcg initialization functions. Now that we are able to pass
a struct mem_cgroup instead of a struct cgroup to the socket
initialization, there is nothing that stops us from initializing
everything in create().

Signed-off-by: Glauber Costa <glommer@parallels.com>
Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
CC: Li Zefan <lizefan@huawei.com>
CC: Johannes Weiner <hannes@cmpxchg.org>
CC: Michal Hocko <mhocko@suse.cz>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 785c323..901bb03 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4640,7 +4640,7 @@ static int mem_control_numa_stat_open(struct inode *unused, struct file *file)
 #endif /* CONFIG_NUMA */
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
-static int register_kmem_files(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
+static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
        return mem_cgroup_sockets_init(memcg, ss);
 };
@@ -4650,7 +4650,7 @@ static void kmem_cgroup_destroy(struct mem_cgroup *memcg)
        mem_cgroup_sockets_destroy(memcg);
 }
 #else
-static int register_kmem_files(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
+static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
        return 0;
 }
@@ -5010,6 +5010,17 @@ mem_cgroup_create(struct cgroup *cont)
        memcg->move_charge_at_immigrate = 0;
        mutex_init(&memcg->thresholds_lock);
        spin_lock_init(&memcg->move_lock);
+
+       error = memcg_init_kmem(memcg, &mem_cgroup_subsys);
+       if (error) {
+               /*
+                * We call put now because our (and parent's) refcnts
+                * are already in place. mem_cgroup_put() will internally
+                * call __mem_cgroup_free, so return directly
+                */
+               mem_cgroup_put(memcg);
+               return ERR_PTR(error);
+       }
        return &memcg->css;
 free_out:
        __mem_cgroup_free(memcg);
@@ -5032,13 +5043,6 @@ static void mem_cgroup_destroy(struct cgroup *cont)
        mem_cgroup_put(memcg);
 }
 
-static int mem_cgroup_populate(struct cgroup_subsys *ss,
-                               struct cgroup *cont)
-{
-       struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
-       return register_kmem_files(memcg, ss);
-}
-
 #ifdef CONFIG_MMU
 /* Handlers for move charge at task migration. */
 #define PRECHARGE_COUNT_AT_ONCE        256
@@ -5622,7 +5626,6 @@ struct cgroup_subsys mem_cgroup_subsys = {
        .create = mem_cgroup_create,
        .pre_destroy = mem_cgroup_pre_destroy,
        .destroy = mem_cgroup_destroy,
-       .populate = mem_cgroup_populate,
        .can_attach = mem_cgroup_can_attach,
        .cancel_attach = mem_cgroup_cancel_attach,
        .attach = mem_cgroup_move_task,