cgroup: set memory.use_hierarchy

But don't fail the container start if that fails.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>

src/lxc/cgroup.c

@@ -81,7 +81,7 @@ static bool cgroup_devices_has_allow_or_deny(struct lxc_handler *h, char *v, boo
 static int do_setup_cgroup(struct lxc_handler *h, struct lxc_list *cgroup_settings, bool do_devices);
 static int cgroup_recursive_task_count(const char *cgroup_path);
 static int count_lines(const char *fn);
-static int handle_clone_children(struct cgroup_mount_point *mp, char *cgroup_path);
+static int handle_cgroup_settings(struct cgroup_mount_point *mp, char *cgroup_path);
 
 struct cgroup_meta_data *lxc_cgroup_load_meta()
 {
@@ -718,7 +718,7 @@ extern struct cgroup_process_info *lxc_cgroup_create(const char *name, const cha
 
 		if (lxc_string_in_array("ns", (const char **)h->subsystems))
 			continue;
-		if (handle_clone_children(mp, info_ptr->cgroup_path) < 0) {
+		if (handle_cgroup_settings(mp, info_ptr->cgroup_path) < 0) {
 			ERROR("Could not set clone_children to 1 for cpuset hierarchy in parent cgroup.");
 			goto out_initial_error;
 		}
@@ -838,7 +838,7 @@ extern struct cgroup_process_info *lxc_cgroup_create(const char *name, const cha
 				/* if we didn't create the cgroup, then we have to make sure that
 				 * further cgroups will be created properly
 				 */
-				if (handle_clone_children(mp, info_ptr->cgroup_path) < 0) {
+				if (handle_cgroup_settings(mp, info_ptr->cgroup_path) < 0) {
 					ERROR("Could not set clone_children to 1 for cpuset hierarchy in pre-existing cgroup.");
 					goto cleanup_from_error;
 				}
@@ -1939,9 +1939,23 @@ int count_lines(const char *fn)
 	return n;
 }
 
-int handle_clone_children(struct cgroup_mount_point *mp, char *cgroup_path)
+int handle_cgroup_settings(struct cgroup_mount_point *mp, char *cgroup_path)
 {
 	int r, saved_errno = 0;
+
+	/* If this is the memory cgroup, we want to enforce hierarchy.
+	 * But don't fail if for some reason we can't.
+	 */
+	if (lxc_string_in_array("memory", (const char **)mp->hierarchy->subsystems)) {
+		char *cc_path = cgroup_to_absolute_path(mp, cgroup_path, "/memory.use_hierarchy");
+		if (cc_path) {
+			r = lxc_write_to_file(cc_path, "1", 1, false);
+			if (r < 0)
+				SYSERROR("failed to set memory.use_hiararchy to 1; continuing");
+			free(cc_path);
+		}
+	}
+
 	/* if this is a cpuset hierarchy, we have to set cgroup.clone_children in
 	 * the base cgroup, otherwise containers will start with an empty cpuset.mems
 	 * and cpuset.cpus and then