memcg: add mem_cgroup_from_css() helper

Add a mem_cgroup_from_css() helper to replace open-coded invokations of
container_of().  To clarify the code and to add a little more type safety.

[akpm@linux-foundation.org: fix extensive breakage]
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 8 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b06833f2b89e..795e525afaba 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -405,6 +405,12 @@ enum charge_type {
 static void mem_cgroup_get(struct mem_cgroup *memcg);
 static void mem_cgroup_put(struct mem_cgroup *memcg);
 
+static inline
+struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
+{
+        return container_of(s, struct mem_cgroup, css);
+}
+
 /* Writing them here to avoid exposing memcg's inner layout */
 #ifdef CONFIG_MEMCG_KMEM
 #include <net/sock.h>
@@ -862,9 +868,8 @@ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
 
 struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
 {
-        return container_of(cgroup_subsys_state(cont,
-                                mem_cgroup_subsys_id), struct mem_cgroup,
-                                css);
+        return mem_cgroup_from_css(
+                cgroup_subsys_state(cont, mem_cgroup_subsys_id));
 }
 
 struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
@@ -877,8 +882,7 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
         if (unlikely(!p))
                 return NULL;
 
-        return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
-                                struct mem_cgroup, css);
+        return mem_cgroup_from_css(task_subsys_state(p, mem_cgroup_subsys_id));
 }
 
 struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
@@ -964,8 +968,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
                 css = css_get_next(&mem_cgroup_subsys, id + 1, &root->css, &id);
                 if (css) {
                         if (css == &root->css || css_tryget(css))
-                                memcg = container_of(css,
-                                                     struct mem_cgroup, css);
+                                memcg = mem_cgroup_from_css(css);
                 } else
                         id = 0;
                 rcu_read_unlock();
@@ -2494,7 +2497,7 @@ static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
         css = css_lookup(&mem_cgroup_subsys, id);
         if (!css)
                 return NULL;
-        return container_of(css, struct mem_cgroup, css);
+        return mem_cgroup_from_css(css);
 }
 
 struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)