static int lxc_one_cgroup_attach(const char *name,
struct mntent *mntent, pid_t pid)
{
FILE *f;
char tasks[MAXPATHLEN], initcgroup[MAXPATHLEN];
char *cgmnt = mntent->mnt_dir;
int flags, ret = 0;
int rc;
flags = get_cgroup_flags(mntent);
rc = snprintf(tasks, MAXPATHLEN, "%s%s%s/%s/tasks", cgmnt,
get_init_cgroup(NULL, mntent, initcgroup),
(flags & CGROUP_NS_CGROUP) ? "" : "/lxc",
name);
if (rc < 0 || rc >= MAXPATHLEN) {
ERROR("pathname too long");
return -1;
}
f = fopen(tasks, "w");
if (!f) {
SYSERROR("failed to open '%s'", tasks);
return -1;
}
if (fprintf(f, "%d", pid) <= 0) {
SYSERROR("failed to write pid '%d' to '%s'", pid, tasks);
ret = -1;
}
fclose(f);
return ret;
}
static int get_cgroup_mount(const char *subsystem, char *mnt)
{
struct mntent *mntent;
char initcgroup[MAXPATHLEN];
FILE *file = NULL;
int ret, flags, err = -1;
file = setmntent(MTAB, "r");
if (!file) {
SYSERROR("failed to open %s", MTAB);
return -1;
}
while ((mntent = getmntent(file))) {
if (strcmp(mntent->mnt_type, "cgroup"))
continue;
if (subsystem) {
if (!hasmntopt(mntent, subsystem))
continue;
}
else {
if (!mount_has_subsystem(mntent))
continue;
}
flags = get_cgroup_flags(mntent);
ret = snprintf(mnt, MAXPATHLEN, "%s%s%s", mntent->mnt_dir,
get_init_cgroup(subsystem, NULL, initcgroup),
(flags & CGROUP_NS_CGROUP) ? "" : "/lxc");
if (ret < 0 || ret >= MAXPATHLEN)
goto fail;
DEBUG("using cgroup mounted at '%s'", mnt);
err = 0;
goto out;
};
fail:
DEBUG("Failed to find cgroup for %s\n",
subsystem ? subsystem : "(NULL)");
out:
endmntent(file);
return err;
}
int lxc_one_cgroup_destroy(struct mntent *mntent, const char *name)
{
char cgname[MAXPATHLEN], initcgroup[MAXPATHLEN];
char *cgmnt = mntent->mnt_dir;
int flags = get_cgroup_flags(mntent);
int rc;
rc = snprintf(cgname, MAXPATHLEN, "%s%s%s/%s", cgmnt,
get_init_cgroup(NULL, mntent, initcgroup),
(flags & CGROUP_NS_CGROUP) ? "" : "/lxc", name);
if (rc < 0 || rc >= MAXPATHLEN) {
ERROR("name too long");
return -1;
}
DEBUG("destroying %s\n", cgname);
if (recursive_rmdir(cgname)) {
SYSERROR("failed to remove cgroup '%s'", cgname);
return -1;
}
DEBUG("'%s' unlinked", cgname);
return 0;
}
int lxc_cgroup_create(const char *name, pid_t pid)
{
char cgmnt[MAXPATHLEN];
char cgname[MAXPATHLEN];
char clonechild[MAXPATHLEN];
int flags;
if (get_cgroup_mount(MTAB, cgmnt)) {
ERROR("cgroup is not mounted");
return -1;
}
snprintf(cgname, MAXPATHLEN, "%s/%s", cgmnt, name);
/*
* There is a previous cgroup, assume it is empty,
* otherwise that fails
*/
if (!access(cgname, F_OK) && rmdir(cgname)) {
SYSERROR("failed to remove previous cgroup '%s'", cgname);
return -1;
}
if (get_cgroup_flags(MTAB, &flags)) {
SYSERROR("failed to get cgroup flags");
return -1;
}
/* We have the deprecated ns_cgroup subsystem */
if (flags & CGROUP_NS_CGROUP) {
WARN("using deprecated ns_cgroup");
return cgroup_rename_nsgroup(cgmnt, cgname, pid);
}
snprintf(clonechild, MAXPATHLEN, "%s/cgroup.clone_children", cgmnt);
/* we check if the kernel has clone_children, at this point if there
* no clone_children neither ns_cgroup, that means the cgroup is mounted
* without the ns_cgroup and it has not the compatibility flag
*/
if (access(clonechild, F_OK)) {
ERROR("no ns_cgroup option specified");
return -1;
}
/* we enable the clone_children flag of the cgroup */
if (cgroup_enable_clone_children(clonechild)) {
SYSERROR("failed to enable 'clone_children flag");
return -1;
}
/* Let's create the cgroup */
if (mkdir(cgname, 0700)) {
SYSERROR("failed to create '%s' directory", cgname);
return -1;
}
/* Let's add the pid to the 'tasks' file */
if (cgroup_attach(cgname, pid)) {
SYSERROR("failed to attach pid '%d' to '%s'", pid, cgname);
rmdir(cgname);
return -1;
}
return 0;
}
/*
* create a cgroup for the container in a particular subsystem.
*/
static int lxc_one_cgroup_create(const char *name,
struct mntent *mntent, pid_t pid)
{
char cginit[MAXPATHLEN], cgname[MAXPATHLEN], cgparent[MAXPATHLEN];
char clonechild[MAXPATHLEN];
char initcgroup[MAXPATHLEN];
int flags, ret;
/* cgparent is the parent dir, e.g., /sys/fs/cgroup/<cgroup>/<init-cgroup>/lxc */
/* (remember get_init_cgroup() returns a path starting with '/') */
/* cgname is the full name, e.g., /sys/fs/cgroup/<cgroup>/<init-cgroup>/lxc/name */
ret = snprintf(cginit, MAXPATHLEN, "%s%s", mntent->mnt_dir,
get_init_cgroup(NULL, mntent, initcgroup));
if (ret < 0 || ret >= MAXPATHLEN) {
SYSERROR("Failed creating pathname for init's cgroup (%d)\n", ret);
return -1;
}
flags = get_cgroup_flags(mntent);
ret = snprintf(cgparent, MAXPATHLEN, "%s%s", cginit,
(flags & CGROUP_NS_CGROUP) ? "" : "/lxc");
if (ret < 0 || ret >= MAXPATHLEN) {
SYSERROR("Failed creating pathname for cgroup parent (%d)\n", ret);
return -1;
}
ret = snprintf(cgname, MAXPATHLEN, "%s/%s", cgparent, name);
if (ret < 0 || ret >= MAXPATHLEN) {
SYSERROR("Failed creating pathname for cgroup (%d)\n", ret);
return -1;
}
/* Do we have the deprecated ns_cgroup subsystem? */
if (flags & CGROUP_NS_CGROUP) {
WARN("using deprecated ns_cgroup");
return cgroup_rename_nsgroup(cginit, name, pid);
}
ret = snprintf(clonechild, MAXPATHLEN, "%s/cgroup.clone_children",
cginit);
if (ret < 0 || ret >= MAXPATHLEN) {
SYSERROR("Failed creating pathname for clone_children (%d)\n", ret);
return -1;
}
/* we check if the kernel has clone_children, at this point if there
* no clone_children neither ns_cgroup, that means the cgroup is mounted
* without the ns_cgroup and it has not the compatibility flag
*/
if (access(clonechild, F_OK)) {
ERROR("no ns_cgroup option specified");
return -1;
}
/* enable the clone_children flag of the cgroup */
if (cgroup_enable_clone_children(clonechild)) {
SYSERROR("failed to enable 'clone_children flag");
return -1;
}
/* if cgparent does not exist, create it */
if (access(cgparent, F_OK) && mkdir(cgparent, 0755)) {
SYSERROR("failed to create '%s' directory", cgparent);
return -1;
}
/*
* There is a previous cgroup. Try to delete it. If that fails
* (i.e. it is not empty) try to move it out of the way.
*/
if (!access(cgname, F_OK) && rmdir(cgname)) {
if (try_to_move_cgname(cgparent, cgname)) {
SYSERROR("failed to remove previous cgroup '%s'", cgname);
return -1;
}
}
/* Let's create the cgroup */
if (mkdir(cgname, 0755)) {
SYSERROR("failed to create '%s' directory", cgname);
return -1;
}
INFO("created cgroup '%s'", cgname);
return 0;
}
