cgroup: pass struct mem_cgroup instead of struct cgroup to socket memcg

The only reason cgroup was used, was to be consistent with the populate()
interface. Now that we're getting rid of it, not only we no longer need
it, but we also *can't* call it this way.

Since we will no longer rely on populate(), this will be called from
create(). During create, the association between struct mem_cgroup
and struct cgroup does not yet exist, since cgroup internals hasn't
yet initialized its bookkeeping. This means we would not be able
to draw the memcg pointer from the cgroup pointer in these
functions, which is highly undesirable.

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>

1 files changed, 9 insertions, 15 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d28359cd6b55..785c32367075 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4640,29 +4640,22 @@ 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 cgroup *cont, struct cgroup_subsys *ss)
+static int register_kmem_files(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
-	/*
-	 * Part of this would be better living in a separate allocation
-	 * function, leaving us with just the cgroup tree population work.
-	 * We, however, depend on state such as network's proto_list that
-	 * is only initialized after cgroup creation. I found the less
-	 * cumbersome way to deal with it to defer it all to populate time
-	 */
-	return mem_cgroup_sockets_init(cont, ss);
+	return mem_cgroup_sockets_init(memcg, ss);
 };
 
-static void kmem_cgroup_destroy(struct cgroup *cont)
+static void kmem_cgroup_destroy(struct mem_cgroup *memcg)
 {
-	mem_cgroup_sockets_destroy(cont);
+	mem_cgroup_sockets_destroy(memcg);
 }
 #else
-static int register_kmem_files(struct cgroup *cont, struct cgroup_subsys *ss)
+static int register_kmem_files(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
 	return 0;
 }
 
-static void kmem_cgroup_destroy(struct cgroup *cont)
+static void kmem_cgroup_destroy(struct mem_cgroup *memcg)
 {
 }
 #endif
@@ -5034,7 +5027,7 @@ static void mem_cgroup_destroy(struct cgroup *cont)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
 
-	kmem_cgroup_destroy(cont);
+	kmem_cgroup_destroy(memcg);
 
 	mem_cgroup_put(memcg);
 }
@@ -5042,7 +5035,8 @@ static void mem_cgroup_destroy(struct cgroup *cont)
 static int mem_cgroup_populate(struct cgroup_subsys *ss,
 				struct cgroup *cont)
 {
-	return register_kmem_files(cont, ss);
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
+	return register_kmem_files(memcg, ss);
 }
 
 #ifdef CONFIG_MMU