add api for generating the list of all controllers (not only mount ones)

this patch add api for generating the list of all controllers (not only mount ones)
- it uses three functions:
cgroup_get_all_controller_begin
cgroup_get_all_controller_next
cgroup_get_all_controller_end

and structure:
struct controller_data {
		char name[FILENAME_MAX];
		int hierarchy;
		int num_cgroups;
		int enabled;
};

the data are read from /proc/cgroups file

Signed-off-by: Ivana Hutarova Varekova <varekova@redhat.com>
Reviewed-by: Jan Safranek <jsafrane@redhat.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>

3 files changed, 112 insertions, 0 deletions

diff --git a/include/libcgroup.h b/include/libcgroup.h
index d3fad97..b8a3a77 100644
--- a/include/libcgroup.h
+++ b/include/libcgroup.h
@@ -155,6 +155,25 @@ struct cgroup_mount_point {
 	char path[FILENAME_MAX];
 };
 
+/*
+ * Detailed information about available controller.
+ */
+
+struct controller_data {
+/** Controller name. */
+	char name[FILENAME_MAX];
+/**
+ * Hierarchy ID. Controllers with the same hierarchy ID
+ * are mounted together as one hierarchy. Controllers with
+ * ID 0 are not currently used.
+ */
+	int hierarchy;
+/** Number of groups. */
+	int num_cgroups;
+/** Enabled flag */
+	int enabled;
+};
+
 /* Functions and structures that can be used by the application*/
 struct cgroup;
 struct cgroup_controller;
@@ -386,6 +405,20 @@ int cgroup_get_controller_begin(void **handle, struct cgroup_mount_point *info);
 int cgroup_get_controller_next(void **handle, struct cgroup_mount_point *info);
 int cgroup_get_controller_end(void **handle);
 
+/**
+ * Read the list of controllers from /proc/cgroups (not mounted included)
+ * @param handle: Handle to be used for iteration.
+ * @param info: The structure which contains all controller data
+ */
+int cgroup_get_all_controller_begin(void **handle,
+	struct controller_data *info);
+/*
+ * While walking through the mount table, the controllers will be
+ * returned in the same order as is in /proc/cgroups file
+ */
+int cgroup_get_all_controller_next(void **handle, struct controller_data *info);
+int cgroup_get_all_controller_end(void **handle);
+
 /*
  * Reads the mount to table to give the mount point of a controller
  * @controller: Name of the controller
diff --git a/src/api.c b/src/api.c
index 727f594..e2399ab 100644
--- a/src/api.c
+++ b/src/api.c
@@ -3232,3 +3232,79 @@ out_exit:
 	pthread_rwlock_unlock(&cg_mount_table_lock);
 	return ret;
 }
+
+
+int cgroup_get_all_controller_end(void **handle)
+{
+	FILE *proc_cgroup = (FILE *) *handle;
+
+	if (!cgroup_initialized)
+		return ECGROUPNOTINITIALIZED;
+
+	if (!proc_cgroup)
+		return ECGINVAL;
+
+	fclose(proc_cgroup);
+	*handle = NULL;
+
+	return 0;
+}
+
+
+int cgroup_get_all_controller_next(void **handle, struct controller_data *info)
+{
+	FILE *proc_cgroup = (FILE *) *handle;
+	int err = 0;
+	int hierarchy, num_cgroups, enabled;
+	char subsys_name[FILENAME_MAX];
+
+	if (!cgroup_initialized)
+		return ECGROUPNOTINITIALIZED;
+
+	if (!proc_cgroup)
+		return ECGINVAL;
+
+	if (!info)
+		return ECGINVAL;
+
+	err = fscanf(proc_cgroup, "%s %d %d %d\n", subsys_name,
+			&hierarchy, &num_cgroups, &enabled);
+
+	if (err != 4)
+		return ECGEOF;
+
+	strncpy(info->name, subsys_name, FILENAME_MAX);
+	info->name[FILENAME_MAX-1] = '\0';
+	info->hierarchy = hierarchy;
+	info->num_cgroups = num_cgroups;
+	info->enabled = enabled;
+
+	return 0;
+}
+
+
+int cgroup_get_all_controller_begin(void **handle, struct controller_data *info)
+{
+	FILE *proc_cgroup = NULL;
+	char buf[FILENAME_MAX];
+
+	if (!cgroup_initialized)
+		return ECGROUPNOTINITIALIZED;
+
+	if (!info)
+		return ECGINVAL;
+
+	proc_cgroup = fopen("/proc/cgroups", "r");
+	if (!proc_cgroup) {
+		last_errno = errno;
+		return ECGOTHER;
+	}
+
+	if (!fgets(buf, FILENAME_MAX, proc_cgroup)) {
+		last_errno = errno;
+		return ECGOTHER;
+	}
+	*handle = proc_cgroup;
+
+	return cgroup_get_all_controller_next(handle, info);
+}
diff --git a/src/libcgroup.map b/src/libcgroup.map
index 66201f2..87d8a51 100644
--- a/src/libcgroup.map
+++ b/src/libcgroup.map
@@ -79,4 +79,7 @@ CGROUP_0.35 {
 global:
 	create_cgroup_from_name_value_pairs;
 	cgroup_delete_cgroup_ext;
+	cgroup_get_all_controller_begin;
+	cgroup_get_all_controller_next;
+	cgroup_get_all_controller_end;
 } CGROUP_0.34;