Sort the cgroup memory settings before applying.

Add a function to sort the cgroup settings before applying.
Currently, the function will put memory.memsw.limit_in_bytes after
memory.limit_in_bytes setting so the container will start
regardless of the order specified in the input. Fix #453

Signed-off-by: Kien Truong <duckientruong@gmail.com>

src/lxc/cgfs.c

@@ -1888,12 +1888,15 @@ static int do_setup_cgroup_limits(struct cgfs_data *d,
 {
 	struct lxc_list *iterator;
 	struct lxc_cgroup *cg;
+	struct lxc_list *sorted_cgroup_settings;
 	int ret = -1;
 
 	if (lxc_list_empty(cgroup_settings))
 		return 0;
 
-	lxc_list_for_each(iterator, cgroup_settings) {
+	sorted_cgroup_settings = sort_cgroup_settings(cgroup_settings);
+
+	lxc_list_for_each(iterator, sorted_cgroup_settings) {
 		cg = iterator->elem;
 
 		if (do_devices == !strncmp("devices", cg->subsystem, 7)) {
@@ -1916,6 +1919,10 @@ static int do_setup_cgroup_limits(struct cgfs_data *d,
 	ret = 0;
 	INFO("cgroup has been setup");
 out:
+	lxc_list_for_each(iterator, sorted_cgroup_settings) {
+		lxc_list_del(iterator);
+		free(iterator);
+	}
 	return ret;
 }
 

src/lxc/cgmanager.c

@@ -1221,6 +1221,7 @@ static bool cgm_setup_limits(void *hdata, struct lxc_list *cgroup_settings, bool
 	struct lxc_list *iterator;
 	struct lxc_cgroup *cg;
 	bool ret = false;
+	struct lxc_list *sorted_cgroup_settings;
 
 	if (lxc_list_empty(cgroup_settings))
 		return true;
@@ -1233,7 +1234,9 @@ static bool cgm_setup_limits(void *hdata, struct lxc_list *cgroup_settings, bool
 		return false;
 	}
 
-	lxc_list_for_each(iterator, cgroup_settings) {
+	sorted_cgroup_settings = sort_cgroup_settings(cgroup_settings);
+
+	lxc_list_for_each(iterator, sorted_cgroup_settings) {
 		char controller[100], *p;
 		cg = iterator->elem;
 		if (do_devices != !strncmp("devices", cg->subsystem, 7))
@@ -1261,6 +1264,10 @@ static bool cgm_setup_limits(void *hdata, struct lxc_list *cgroup_settings, bool
 	ret = true;
 	INFO("cgroup limits have been setup");
 out:
+	lxc_list_for_each(iterator, sorted_cgroup_settings) {
+		lxc_list_del(iterator);
+		free(iterator);
+	}
 	cgm_dbus_disconnect();
 	return ret;
 }

src/lxc/conf.c

@@ -4557,3 +4557,38 @@ void suggest_default_idmap(void)
 	free(gname);
 	free(uname);
 }
+
+/*
+ * Return the list of cgroup_settings sorted according to the following rules
+ * 1. Put memory.limit_in_bytes before memory.memsw.limit_in_bytes
+ */
+struct lxc_list *sort_cgroup_settings(struct lxc_list* cgroup_settings)
+{
+	struct lxc_list *result;
+	struct lxc_list *memsw_limit = NULL;
+	struct lxc_list *it = NULL;
+	struct lxc_cgroup *cg = NULL;
+	struct lxc_list *item = NULL;
+
+	result = malloc(sizeof(*result));
+	lxc_list_init(result);
+
+	/*Iterate over the cgroup settings and copy them to the output list*/
+	lxc_list_for_each(it, cgroup_settings) {
+		item = malloc(sizeof(*item));
+		item->elem = it->elem;
+		cg = it->elem;
+		if (strcmp(cg->subsystem, "memory.memsw.limit_in_bytes") == 0) {
+			/* Store the memsw_limit location */
+			memsw_limit = item;
+		} else if (strcmp(cg->subsystem, "memory.limit_in_bytes") == 0 && memsw_limit != NULL) {
+			/* lxc.cgroup.memory.memsw.limit_in_bytes is found before 
+			 * lxc.cgroup.memory.limit_in_bytes, swap these two items */
+			item->elem = memsw_limit->elem;
+			memsw_limit->elem = it->elem;
+		}
+		lxc_list_add_tail(result, item);
+	}
+
+	return result;
+}

src/lxc/conf.h

@@ -430,4 +430,5 @@ extern void tmp_proc_unmount(struct lxc_conf *lxc_conf);
 void remount_all_slave(void);
 extern void suggest_default_idmap(void);
 FILE *write_mount_file(struct lxc_list *mount);
+struct lxc_list *sort_cgroup_settings(struct lxc_list* cgroup_settings);
 #endif