cgroups: use hierarchy_mutex in memory controller

Update the memory controller to use its hierarchy_mutex rather than
calling cgroup_lock() to protected against cgroup_mkdir()/cgroup_rmdir()
from occurring in its hierarchy.

Signed-off-by: Paul Menage <menage@google.com>
Tested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 8 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 93a792871804..e2996b80601f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -154,7 +154,7 @@ struct mem_cgroup {
 
         /*
          * While reclaiming in a hiearchy, we cache the last child we
-         * reclaimed from. Protected by cgroup_lock()
+         * reclaimed from. Protected by hierarchy_mutex
          */
         struct mem_cgroup *last_scanned_child;
         /*
@@ -615,7 +615,7 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
 
 /*
  * This routine finds the DFS walk successor. This routine should be
- * called with cgroup_mutex held
+ * called with hierarchy_mutex held
  */
 static struct mem_cgroup *
 mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem)
@@ -685,7 +685,7 @@ mem_cgroup_get_first_node(struct mem_cgroup *root_mem)
         /*
          * Scan all children under the mem_cgroup mem
          */
-        cgroup_lock();
+        mutex_lock(&mem_cgroup_subsys.hierarchy_mutex);
         if (list_empty(&root_mem->css.cgroup->children)) {
                 ret = root_mem;
                 goto done;
@@ -706,7 +706,7 @@ mem_cgroup_get_first_node(struct mem_cgroup *root_mem)
 
 done:
         root_mem->last_scanned_child = ret;
-        cgroup_unlock();
+        mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex);
         return ret;
 }
 
@@ -770,18 +770,16 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
         while (next_mem != root_mem) {
                 if (mem_cgroup_is_obsolete(next_mem)) {
                         mem_cgroup_put(next_mem);
-                        cgroup_lock();
                         next_mem = mem_cgroup_get_first_node(root_mem);
-                        cgroup_unlock();
                         continue;
                 }
                 ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap,
                                                    get_swappiness(next_mem));
                 if (mem_cgroup_check_under_limit(root_mem))
                         return 0;
-                cgroup_lock();
+                mutex_lock(&mem_cgroup_subsys.hierarchy_mutex);
                 next_mem = mem_cgroup_get_next_node(next_mem, root_mem);
-                cgroup_unlock();
+                mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex);
         }
         return ret;
 }