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>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 93a7928..e2996b8 100644 (file)
--- 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;
 }