libcgroup: Introduce a unload cgroups API

This API will unload the cgroups created in the cgroupfs and
unmount and delete the filesystem mount point. The action is
equivalent to what is done currently in service cgconfig stop.

The reason for this API is to make sure we don't end up with a
asymmetric library API subset. Today an application program can
programatically through cgroup_config_load_config() load a
configuration file, but has no means to cleanup (including all
temporarily created groups).

changes from v3
1. Address Jan's comments from http://article.gmane.org/gmane.comp.lib.libcg.devel/1105
changes from v2
1. Fix a leak as noted by Bharata
2. Address Balbir's review comments at
http://article.gmane.org/gmane.comp.lib.libcg.devel/1080
changes from v1
1. Change the name of the function to cgroup_unload_cgroups
2. Change the name of the executatble to cgclear
3. Split out the funtions

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>

5 files changed, 216 insertions, 1 deletions

diff --git a/include/libcgroup.h b/include/libcgroup.h
index e2abdc8..ce0d8a5 100644
--- a/include/libcgroup.h
+++ b/include/libcgroup.h
@@ -368,6 +368,7 @@ struct cgroup_controller *cgroup_get_controller(struct cgroup *cgroup,
  * Config related stuff
  */
 int cgroup_config_load_config(const char *pathname);
+int cgroup_unload_cgroups(void);
 
 __END_DECLS
 
diff --git a/src/config.c b/src/config.c
index 5706e1d..5d5155f 100644
--- a/src/config.c
+++ b/src/config.c
@@ -492,3 +492,177 @@ err_mnt:
 	fclose(yyin);
 	return error;
 }
+
+static int cgroup_cleanup_cgroup_controller_files(struct cgroup_file_info info,
+						char *root_path, char *ctrl)
+{
+	void *task_handle;
+	pid_t pid;
+	char *rel_path = NULL;
+	int error;
+	int ret;
+
+
+	rel_path = info.full_path + strlen(root_path) - 1;
+
+	if (!strncmp(rel_path, "/", strlen(rel_path)))
+		return 0;
+
+	error = cgroup_get_task_begin(rel_path, ctrl,
+					&task_handle, &pid);
+
+	if (error && error != ECGEOF)
+		return error;
+
+	while (error != ECGEOF) {
+		ret = cgroup_attach_task_pid(NULL, pid);
+
+		if (ret) {
+			cgroup_get_task_end(&task_handle);
+			return ret;
+		}
+		error = cgroup_get_task_next(&task_handle, &pid);
+
+		if (error && error != ECGEOF) {
+			cgroup_get_task_end(&task_handle);
+			return error;
+		}
+	}
+
+	cgroup_get_task_end(&task_handle);
+
+	error = rmdir(info.full_path);
+	if (error) {
+		last_errno = errno;
+		return ECGOTHER;
+	}
+
+	return 0;
+}
+
+static int cgroup_config_unload_controller(struct cgroup_mount_point mount_info)
+{
+	struct cgroup_file_info info;
+	void *tree_handle;
+	int lvl;
+	int ret = 0, error;
+	char *root_path = NULL;
+
+	error = cgroup_walk_tree_begin(mount_info.name, "/", 0, &tree_handle,
+							&info, &lvl);
+
+	if (error && error != ECGEOF)
+		return error;
+
+	root_path = strdup(info.full_path);
+
+	if (!root_path) {
+		cgroup_walk_tree_end(&tree_handle);
+		last_errno = errno;
+		return ECGOTHER;
+	}
+
+	ret = cgroup_walk_tree_set_flags(&tree_handle,
+				CGROUP_WALK_TYPE_POST_DIR);
+
+	if (ret) {
+		cgroup_walk_tree_end(&tree_handle);
+		goto out_error;
+	}
+
+	while (error != ECGEOF) {
+		if (info.type == CGROUP_FILE_TYPE_DIR) {
+			ret = cgroup_cleanup_cgroup_controller_files(info,
+						root_path, mount_info.name);
+
+			if (ret) {
+				cgroup_walk_tree_end(&tree_handle);
+				goto out_error;
+			}
+		}
+
+		error = cgroup_walk_tree_next(0, &tree_handle, &info, lvl);
+
+		if (error && error != ECGEOF) {
+			ret = error;
+			cgroup_walk_tree_end(&tree_handle);
+		}
+	}
+	cgroup_walk_tree_end(&tree_handle);
+	error = umount(mount_info.path);
+
+	if (error) {
+		last_errno = errno;
+		ret = ECGOTHER;
+		goto out_error;
+	}
+
+	error = rmdir(mount_info.path);
+
+	if (error) {
+		last_errno = errno;
+		ret = ECGOTHER;
+	}
+
+out_error:
+	free(root_path);
+	return ret;
+}
+
+int cgroup_unload_cgroups(void)
+{
+	int error = 0;
+	void *ctrl_handle;
+	int ret = 0;
+	char *curr_path = NULL;
+	struct cgroup_mount_point info;
+
+	error = cgroup_init();
+
+	if (error) {
+		ret = error;
+		goto out_error;
+	}
+
+	error = cgroup_get_controller_begin(&ctrl_handle, &info);
+
+
+	if (error && error != ECGEOF) {
+		ret = error;
+		goto out_error;
+	}
+
+	while (error != ECGEOF) {
+		if (!curr_path || strcmp(info.path, curr_path) != 0) {
+			if (curr_path)
+				free(curr_path);
+
+			curr_path = strdup(info.path);
+			if (!curr_path)
+				goto out_errno;
+
+			ret = cgroup_config_unload_controller(info);
+
+			if (ret)
+				goto out_error;
+		}
+
+		error = cgroup_get_controller_next(&ctrl_handle, &info);
+
+		if (error && error != ECGEOF) {
+			ret = error;
+			goto out_error;
+		}
+	}
+
+out_error:
+	if (curr_path)
+		free(curr_path);
+	cgroup_get_controller_end(&ctrl_handle);
+	return ret;
+
+out_errno:
+	last_errno = errno;
+	cgroup_get_controller_end(&ctrl_handle);
+	return ECGOTHER;
+}
diff --git a/src/libcgroup.map b/src/libcgroup.map
index adcf905..5b088d4 100644
--- a/src/libcgroup.map
+++ b/src/libcgroup.map
@@ -66,6 +66,7 @@ global:
 	cgroup_get_controller_end;
 	cgroup_get_controller_next;
 	cgroup_get_controller_begin;
+	cgroup_unload_cgroups;
 	cgroup_get_controller;
 	cgroup_get_uid_gid_from_procfs;
 } CGROUP_0.33;
diff --git a/src/tools/Makefile.am b/src/tools/Makefile.am
index 2b4c9e7..f82916c 100644
--- a/src/tools/Makefile.am
+++ b/src/tools/Makefile.am
@@ -5,7 +5,7 @@ if WITH_TOOLS
 
 bin_PROGRAMS = cgexec cgclassify cgcreate cgset
 
-sbin_PROGRAMS = cgconfigparser
+sbin_PROGRAMS = cgconfigparser cgclear
 
 cgexec_SOURCES = cgexec.c tools-common.c tools-common.h
 
@@ -15,4 +15,6 @@ cgcreate_SOURCES = cgcreate.c tools-common.c tools-common.h
 
 cgconfigparser_SOURCES = cgconfig.c
 
+cgclear_SOURCES = cgclear.c
+
 endif
diff --git a/src/tools/cgclear.c b/src/tools/cgclear.c
new file mode 100644
index 0000000..1485768
--- /dev/null
+++ b/src/tools/cgclear.c
@@ -0,0 +1,37 @@
+/*
+ * Copyright IBM Corporation. 2009
+ *
+ * Authors:	Dhaval Giani <dhaval@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Code initiated and designed by Dhaval Giani. All faults are most likely
+ * his mistake.
+ */
+
+#include <libcgroup.h>
+#include <libcgroup-internal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+int main(int argc, char *argv[])
+{
+	int error;
+
+	error = cgroup_unload_cgroups();
+
+	if (error) {
+		printf("%s failed with %s\n", argv[0], cgroup_strerror(error));
+		exit(3);
+	}
+
+	return 0;
+}