1 files changed, 325 insertions, 0 deletions
diff --git a/balbir/api.c b/balbir/api.c
new file mode 100644
index 0000000..df594ea
--- /dev/null
+++ b/balbir/api.c
@@ -0,0 +1,325 @@
+/*
+ * Copyright IBM Corporation. 2007
+ *
+ * Author:	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.
+ *
+ * TODOs:
+ *	1. Convert comments to Docbook style.
+ *	2. Add more APIs for the control groups.
+ *	3. Handle the configuration related APIs.
+ *	4. Error handling.
+ *
+ * Code initiated and designed by Dhaval Giani. All faults are most likely
+ * his mistake.
+ */
+
+#include <errno.h>
+#include <libcg.h>
+#include <mntent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+static char MOUNT_POINT[FILENAME_MAX];
+
+int cg_init()
+{
+	FILE *proc_mount;
+	struct mntent *ent;
+
+	proc_mount = fopen("/proc/mounts", "r");
+	ent = getmntent(proc_mount);
+
+	while (strcmp(ent->mnt_fsname,"cgroup") != 0) {
+		ent = getmntent(proc_mount);
+		if (ent == NULL)
+			return ECGROUPNOTMOUNTED;
+	}
+	strcpy(MOUNT_POINT, ent->mnt_dir);
+	fclose(proc_mount);
+	return 0;
+}
+
+static int cg_test_mounted_fs()
+{
+	FILE *proc_mount;
+	struct mntent *ent;
+
+	proc_mount = fopen("/proc/mounts", "r");
+	if (proc_mount == NULL) {
+		return -1;
+	}
+	ent = getmntent(proc_mount);
+
+	while (strcmp(ent->mnt_fsname, "cgroup") !=0) {
+		ent = getmntent(proc_mount);
+		if (ent == NULL)
+			return 0;
+	}
+	fclose(proc_mount);
+	return 1;
+}
+
+static inline pid_t cg_gettid()
+{
+	return syscall(__NR_gettid);
+}
+
+static char* cg_build_path(char *name, char *path)
+{
+	strcpy(path, MOUNT_POINT);
+	strcat(path, name);
+	strcat(path, "/");
+	return path;
+}
+
+/** cg_attach_task_pid is used to assign tasks to a cgroup.
+ *  struct cgroup *cgroup: The cgroup to assign the thread to.
+ *  pid_t tid: The thread to be assigned to the cgroup.
+ *
+ *  returns 0 on success.
+ *  returns ECGROUPNOTOWNER if the caller does not have access to the cgroup.
+ *  returns ECGROUPNOTALLOWED for other causes of failure.
+ */
+int cg_attach_task_pid(struct cgroup *cgroup, pid_t tid)
+{
+	char path[FILENAME_MAX];
+	FILE *tasks;
+
+	if (cgroup == NULL)
+		strcpy(path, MOUNT_POINT);
+	else {
+		cg_build_path(cgroup->name, path);
+	}
+
+	strcat(path, "/tasks");
+
+	tasks = fopen(path, "w");
+	if (!tasks) {
+		switch (errno) {
+		case EPERM:
+			return ECGROUPNOTOWNER;
+		default:
+			return ECGROUPNOTALLOWED;
+		}
+	}
+	fprintf(tasks, "%d", tid);
+	fclose(tasks);
+
+	return 0;
+
+}
+
+/** cg_attach_task is used to attach the current thread to a cgroup.
+ *  struct cgroup *cgroup: The cgroup to assign the current thread to.
+ *
+ *  See cg_attach_task_pid for return values.
+ */
+int cg_attach_task(struct cgroup *cgroup)
+{
+	pid_t tid = cg_gettid();
+	int error;
+
+	error = cg_attach_task_pid(cgroup, tid);
+
+	return error;
+}
+
+/*
+ * create_control_group()
+ * This is the basic function used to create the control group. This function
+ * just makes the group. It does not set any permissions, or any control values.
+ * The argument path is the fully qualified path name to make it generic.
+ */
+static int cg_create_control_group(char *path)
+{
+	int error;
+	if (!cg_test_mounted_fs())
+		return ECGROUPNOTMOUNTED;
+	error = mkdir(path, 0700);
+	if (!error) {
+		switch(errno) {
+		case EPERM:
+			return ECGROUPNOTOWNER;
+		default:
+			return ECGROUPNOTALLOWED;
+		}
+	}
+	return error;
+}
+
+/*
+ * set_control_value()
+ * This is the low level function for putting in a value in a control file.
+ * This function takes in the complete path and sets the value in val in that
+ * file.
+ *
+ * TODO:
+ * At this point I am not sure what all values the control file can take. So
+ * I put in an int arg. But this has to be made much more robust.
+ */
+static int cg_set_control_value(char *path, char *val)
+{
+	int error;
+	FILE *control_file;
+	if (!cg_test_mounted_fs())
+		return ECGROUPNOTMOUNTED;
+
+	control_file = fopen(path, "a");
+
+	if (!control_file) {
+		if (errno == EPERM) {
+			/*
+			 * We need to set the correct error value, does the
+			 * group exist but we don't have the subsystem
+			 * mounted at that point, or is it that the group
+			 * does not exist. So we check if the tasks file
+			 * exist. Before that, we need to extract the path.
+			 */
+			int len = strlen(path);
+
+			while (*(path+len) != '/')
+				len--;
+			*(path+len+1) = '\0';
+			strcat(path, "tasks");
+			control_file = fopen(path, "r");
+			if (!control_file) {
+				if (errno == ENOENT)
+					return ECGROUPSUBSYSNOTMOUNTED;
+			}
+			fclose(control_file);
+			return ECGROUPNOTALLOWED;
+		}
+	}
+
+	fprintf(control_file, "%s", val);
+	fclose(control_file);
+	return 0;
+}
+
+/** cg_modify_cgroup modifies the cgroup control files.
+ * struct cgroup *cgroup: The name will be the cgroup to be modified.
+ * The values will be the values to be modified, those not mentioned
+ * in the structure will not be modified.
+ *
+ * The uids cannot be modified yet.
+ *
+ * returns 0 on success.
+ *
+ */
+
+int cg_modify_cgroup(struct cgroup *cgroup)
+{
+	char path[FILENAME_MAX], base[FILENAME_MAX];
+	int i;
+	int error;
+
+	cg_build_path(cgroup->name, base);
+
+	for (i = 0; i < CG_CONTROLLER_MAX && cgroup->controller[i];
+						i++, strcpy(path, base)) {
+		int j;
+		for(j = 0; j < CG_NV_MAX &&
+			cgroup->controller[i]->values[j];
+			j++, strcpy(path, base)) {
+			strcat(path, cgroup->controller[i]->values[j]->name);
+			error = cg_set_control_value(path,
+				cgroup->controller[i]->values[j]->value);
+			if (error)
+				goto err;
+		}
+	}
+	return 0;
+err:
+	return error;
+
+}
+
+/** create_cgroup creates a new control group.
+ * struct cgroup *cgroup: The control group to be created
+ *
+ * returns 0 on success.
+ */
+int cg_create_cgroup(struct cgroup *cgroup)
+{
+	char path[FILENAME_MAX], base[FILENAME_MAX];
+	int i;
+	int error;
+
+	if (MOUNT_POINT == NULL)
+		return ECGROUPNOTMOUNTED;
+
+	cg_build_path(cgroup->name, path);
+
+	error = cg_create_control_group(path);
+
+	strcpy(base, path);
+
+	for (i = 0; i < CG_CONTROLLER_MAX && cgroup->controller[i];
+						i++, strcpy(path, base)) {
+		int j;
+		for(j = 0; j < CG_NV_MAX && cgroup->controller[i]->values[j];
+						j++, strcpy(path, base)) {
+			strcat(path, cgroup->controller[i]->values[j]->name);
+			error = cg_set_control_value(path,
+					cgroup->controller[i]->values[j]->value);
+			chown(path, cgroup->control_uid, cgroup->control_gid);
+			if (!error)
+				return error;
+		}
+	}
+	strcpy(path, base);
+	strcat(path, "tasks");
+	chown(path, cgroup->tasks_uid, cgroup->tasks_gid);
+	return error;
+}
+
+/** cg_delete cgroup deletes a control group.
+ *  struct cgroup *cgroup takes the group which is to be deleted.
+ *
+ *  returns 0 on success.
+ */
+int cg_delete_cgroup(struct cgroup *cgroup)
+{
+	FILE *delete_tasks, *base_tasks;
+	int tids;
+	char path[FILENAME_MAX];
+	int error;
+
+	strcpy(path, MOUNT_POINT);
+	strcat(path,"/tasks");
+
+	base_tasks = fopen(path, "w");
+
+	cg_build_path(cgroup->name, path);
+	strcat(path,"tasks");
+
+	delete_tasks = fopen(path, "r");
+
+	while (!feof(delete_tasks)) {
+		fscanf(delete_tasks, "%d", &tids);
+		fprintf(base_tasks, "%d", tids);
+	}
+
+	cg_build_path(cgroup->name, path);
+
+	error = rmdir(path);
+
+	if (!error) {
+			return ECGROUPNOTALLOWED;
+		}
+
+	return error;
+}