cgroup: add new functions for interacting with hierachies

src/lxc/cgroups/cgfs.c

@@ -2434,6 +2434,18 @@ out:
 	return ret;
 }
 
+static int cgfs_num_hierarchies(void)
+{
+	/* not implemented */
+	return -1;
+}
+
+static bool cgfs_get_hierarchies(int i, char ***out)
+{
+	/* not implemented */
+	return false;
+}
+
 static bool cgfs_unfreeze(void *hdata)
 {
 	struct cgfs_data *d = hdata;
@@ -2627,6 +2639,8 @@ static struct cgroup_ops cgfs_ops = {
 	.get_cgroup = cgfs_get_cgroup,
 	.canonical_path = cgfs_canonical_path,
 	.escape = cgfs_escape,
+	.num_hierarchies = cgfs_num_hierarchies,
+	.get_hierarchies = cgfs_get_hierarchies,
 	.get = lxc_cgroupfs_get,
 	.set = lxc_cgroupfs_set,
 	.unfreeze = cgfs_unfreeze,

src/lxc/cgroups/cgfsng.c

@@ -1457,6 +1457,31 @@ out:
 	return ret;
 }
 
+static int cgfsng_num_hierarchies(void)
+{
+	int i;
+
+	for (i = 0; hierarchies[i]; i++)
+		;
+
+	return i;
+}
+
+static bool cgfsng_get_hierarchies(int n, char ***out)
+{
+	int i;
+
+	/* sanity check n */
+	for (i = 0; i < n; i++) {
+		if (!hierarchies[i])
+			return false;
+	}
+
+	*out = hierarchies[i]->controllers;
+
+	return true;
+}
+
 #define THAWED "THAWED"
 #define THAWED_LEN (strlen(THAWED))
 
@@ -1674,6 +1699,8 @@ static struct cgroup_ops cgfsng_ops = {
 	.enter = cgfsng_enter,
 	.canonical_path = cgfsng_canonical_path,
 	.escape = cgfsng_escape,
+	.num_hierarchies = cgfsng_num_hierarchies,
+	.get_hierarchies = cgfsng_get_hierarchies,
 	.get_cgroup = cgfsng_get_cgroup,
 	.get = cgfsng_get,
 	.set = cgfsng_set,

src/lxc/cgroups/cgmanager.c

@@ -337,6 +337,18 @@ static bool cgm_escape(void *hdata)
 	return ret;
 }
 
+static int cgm_num_hierarchies(void)
+{
+	/* not implemented */
+	return -1;
+}
+
+static bool cgm_get_hierarchies(int i, char ***out)
+{
+	/* not implemented */
+	return false;
+}
+
 struct chown_data {
 	const char *cgroup_path;
 	uid_t origuid;
@@ -1657,6 +1669,8 @@ static struct cgroup_ops cgmanager_ops = {
 	.get_cgroup = cgm_get_cgroup,
 	.canonical_path = cgm_canonical_path,
 	.escape = cgm_escape,
+	.num_hierarchies = cgm_num_hierarchies,
+	.get_hierarchies = cgm_get_hierarchies,
 	.get = cgm_get,
 	.set = cgm_set,
 	.unfreeze = cgm_unfreeze,

src/lxc/cgroups/cgroup.c

@@ -132,6 +132,22 @@ const char *cgroup_canonical_path(struct lxc_handler *handler)
 	return NULL;
 }
 
+int cgroup_num_hierarchies(void)
+{
+	if (!ops)
+		return -1;
+
+	return ops->num_hierarchies();
+}
+
+bool cgroup_get_hierarchies(int n, char ***out)
+{
+	if (!ops)
+		return false;
+
+	return ops->get_hierarchies(n, out);
+}
+
 bool cgroup_unfreeze(struct lxc_handler *handler)
 {
 	if (ops)

src/lxc/cgroups/cgroup.h

@@ -49,6 +49,8 @@ struct cgroup_ops {
 	const char *(*get_cgroup)(void *hdata, const char *subsystem);
 	const char *(*canonical_path)(void *hdata);
 	bool (*escape)();
+	int (*num_hierarchies)();
+	bool (*get_hierarchies)(int n, char ***out);
 	int (*set)(const char *filename, const char *value, const char *name, const char *lxcpath);
 	int (*get)(const char *filename, char *value, size_t len, const char *name, const char *lxcpath);
 	bool (*unfreeze)(void *hdata);
@@ -74,6 +76,8 @@ extern bool cgroup_create_legacy(struct lxc_handler *handler);
 extern int cgroup_nrtasks(struct lxc_handler *handler);
 extern const char *cgroup_get_cgroup(struct lxc_handler *handler, const char *subsystem);
 extern bool cgroup_escape();
+extern int cgroup_num_hierarchies();
+extern bool cgroup_get_hierarchies(int i, char ***out);
 
 /*
  * Currently, this call  only makes sense for privileged containers.