libcgroup: Introduce get_controller API

This set of APIs will allow the caller to query the mount table
and find out what controller is mounted at what path.

Test program has been included in the patch. Running the test program
results in

[dhaval@gondor tests]$ ../libtool --mode=execute ./get_controller
Controller cpu is mounted at /cgroup
Controller cpuacct is mounted at /cgroup
Controller memory is mounted at /cgroup1
[dhaval@gondor tests]$

Which is the setup on this system.

Changes from v2
1. Remove the incorrect comments as pointed out by Bharata

Changes from v1
1. Use a new structure as mentioned by bharata to return the values.

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Jan Safranek <jsafrane@redhat.com>
Acked-by: Bharata B Rao <bharata@linux.vnet.ibm.com>

2 files changed, 36 insertions, 1 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index 41aebd3..e8401f2 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -2,7 +2,7 @@ INCLUDES = -I$(top_srcdir)/include
 LDADD = $(top_srcdir)/src/.libs/libcgroup.la
 
 # compile the tests, but do not install them
-noinst_PROGRAMS = libcgrouptest01 libcg_ba setuid pathtest walk_test read_stats walk_task
+noinst_PROGRAMS = libcgrouptest01 libcg_ba setuid pathtest walk_test read_stats walk_task get_controller
 
 libcgrouptest01_SOURCES=libcgrouptest01.c test_functions.c libcgrouptest.h
 libcg_ba_SOURCES=libcg_ba.cpp
@@ -11,6 +11,7 @@ pathtest_SOURCES=pathtest.c
 walk_test_SOURCES=walk_test.c
 read_stats_SOURCES=read_stats.c
 walk_task_SOURCES=walk_task.c
+get_controller_SOURCES=get_controller.c
 
 EXTRA_DIST = pathtest.sh runlibcgrouptest.sh
 
diff --git a/tests/get_controller.c b/tests/get_controller.c
new file mode 100644
index 0000000..1829f5c
--- /dev/null
+++ b/tests/get_controller.c
@@ -0,0 +1,34 @@
+#include <libcgroup.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int main()
+{
+	int error;
+	void *handle;
+	struct cgroup_mount_point info;
+
+	error = cgroup_init();
+
+	if (error) {
+		printf("cgroup_init failed with %s\n", cgroup_strerror(error));
+		exit(1);
+	}
+
+	error = cgroup_get_controller_begin(&handle, &info);
+
+	while (error != ECGEOF) {
+		printf("Controller %s is mounted at %s\n", info.name,
+								info.path);
+		error = cgroup_get_controller_next(&handle, &info);
+		if (error && error != ECGEOF) {
+			printf("cgroup_get_contrller_next failed with %s",
+							cgroup_strerror(error));
+			exit(1);
+		}
+	}
+
+	error = cgroup_get_controller_end(&handle);
+
+	return 0;
+}