1 files changed, 57 insertions, 4 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 20e1d90b3363..886e2224c5fd 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -149,6 +149,10 @@ struct mem_cgroup {
          * reclaimed from. Protected by cgroup_lock()
          */
         struct mem_cgroup *last_scanned_child;
+        /*
+         * Should the accounting and control be hierarchical, per subtree?
+         */
+        bool use_hierarchy;
 
         int             obsolete;
         atomic_t        refcnt;
@@ -1543,6 +1547,44 @@ int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
 }
 
 
+static u64 mem_cgroup_hierarchy_read(struct cgroup *cont, struct cftype *cft)
+{
+        return mem_cgroup_from_cont(cont)->use_hierarchy;
+}
+
+static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
+                                        u64 val)
+{
+        int retval = 0;
+        struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
+        struct cgroup *parent = cont->parent;
+        struct mem_cgroup *parent_mem = NULL;
+
+        if (parent)
+                parent_mem = mem_cgroup_from_cont(parent);
+
+        cgroup_lock();
+        /*
+         * If parent's use_hiearchy is set, we can't make any modifications
+         * in the child subtrees. If it is unset, then the change can
+         * occur, provided the current cgroup has no children.
+         *
+         * For the root cgroup, parent_mem is NULL, we allow value to be
+         * set if there are no children.
+         */
+        if ((!parent_mem || !parent_mem->use_hierarchy) &&
+                                (val == 1 || val == 0)) {
+                if (list_empty(&cont->children))
+                        mem->use_hierarchy = val;
+                else
+                        retval = -EBUSY;
+        } else
+                retval = -EINVAL;
+        cgroup_unlock();
+
+        return retval;
+}
+
 static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
 {
         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
@@ -1706,6 +1748,11 @@ static struct cftype mem_cgroup_files[] = {
                 .name = "force_empty",
                 .trigger = mem_cgroup_force_empty_write,
         },
+        {
+                .name = "use_hierarchy",
+                .write_u64 = mem_cgroup_hierarchy_write,
+                .read_u64 = mem_cgroup_hierarchy_read,
+        },
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
@@ -1881,12 +1928,18 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
         if (cont->parent == NULL) {
                 enable_swap_cgroup();
                 parent = NULL;
-        } else
+        } else {
                 parent = mem_cgroup_from_cont(cont->parent);
+                mem->use_hierarchy = parent->use_hierarchy;
+        }
 
-        res_counter_init(&mem->res, parent ? &parent->res : NULL);
-        res_counter_init(&mem->memsw, parent ? &parent->memsw : NULL);
-
+        if (parent && parent->use_hierarchy) {
+                res_counter_init(&mem->res, &parent->res);
+                res_counter_init(&mem->memsw, &parent->memsw);
+        } else {
+                res_counter_init(&mem->res, NULL);
+                res_counter_init(&mem->memsw, NULL);
+        }
 
         mem->last_scanned_child = NULL;