/*
* for each mounted cgroup, destroy the cgroup for the container
*/
int lxc_cgroup_destroy(const char *name)
{
struct mntent *mntent;
FILE *file = NULL;
int 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 (!mount_has_subsystem(mntent))
continue;
err = lxc_one_cgroup_destroy(mntent, name);
if (err)
break;
}
endmntent(file);
return err;
}
/*
* for each mounted cgroup, destroy the cgroup for the container
*/
int lxc_cgroup_destroy(const char *cgpath)
{
struct mntent *mntent;
FILE *file = NULL;
int err, retv = 0;
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 (!mount_has_subsystem(mntent))
continue;
err = lxc_one_cgroup_destroy(mntent, cgpath);
if (err) // keep trying to clean up the others
retv = -1;
}
endmntent(file);
return retv;
}
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;
}
/*
* Make sure the 'cgroup group' exists, so that we don't have to worry about
* that later.
*
* @lxcgroup: the cgroup group, i.e. 'lxc' by default.
*
* See detailed comments at lxc_cgroup_path_create for more information.
*
* Returns 0 on success, -1 on error.
*/
static int create_lxcgroups(const char *lxcgroup)
{
FILE *file = NULL;
struct mntent *mntent;
int ret, retv = -1;
char path[MAXPATHLEN];
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 (!mount_has_subsystem(mntent))
continue;
/*
* TODO - handle case where lxcgroup has subdirs? (i.e. build/l1)
* We probably only want to support that for /users/joe
*/
ret = snprintf(path, MAXPATHLEN, "%s/%s",
mntent->mnt_dir, lxcgroup ? lxcgroup : "lxc");
if (ret < 0 || ret >= MAXPATHLEN)
goto fail;
if (access(path, F_OK)) {
set_clone_children(mntent->mnt_dir);
ret = mkdir(path, 0755);
if (ret == -1 && errno != EEXIST) {
SYSERROR("failed to create '%s' directory", path);
goto fail;
}
}
}
retv = 0;
fail:
endmntent(file);
return retv;
}
/*
* for each mounted cgroup, create a cgroup for the container and attach a pid
*/
int lxc_cgroup_create(const char *name, pid_t pid)
{
struct mntent *mntent;
FILE *file = NULL;
int err = -1;
int found = 0;
file = setmntent(MTAB, "r");
if (!file) {
SYSERROR("failed to open %s", MTAB);
return -1;
}
while ((mntent = getmntent(file))) {
DEBUG("checking '%s' (%s)", mntent->mnt_dir, mntent->mnt_type);
if (strcmp(mntent->mnt_type, "cgroup"))
continue;
if (!mount_has_subsystem(mntent))
continue;
INFO("[%d] found cgroup mounted at '%s',opts='%s'",
++found, mntent->mnt_dir, mntent->mnt_opts);
err = lxc_one_cgroup_create(name, mntent, pid);
if (err)
goto out;
err = lxc_one_cgroup_attach(name, mntent, pid);
if (err)
goto out;
};
if (!found)
ERROR("No cgroup mounted on the system");
out:
endmntent(file);
return err;
}
int lxc_cgroup_enter(const char *cgpath, pid_t pid)
{
char path[MAXPATHLEN];
FILE *file = NULL, *fout;
struct mntent *mntent;
int ret, retv = -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 (!mount_has_subsystem(mntent))
continue;
ret = snprintf(path, MAXPATHLEN, "%s/%s/tasks",
mntent->mnt_dir, cgpath);
if (ret < 0 || ret >= MAXPATHLEN) {
ERROR("entering cgroup");
goto out;
}
fout = fopen(path, "w");
if (!fout) {
ERROR("entering cgroup");
goto out;
}
fprintf(fout, "%d\n", (int)pid);
fclose(fout);
}
retv = 0;
out:
endmntent(file);
return retv;
}
/*
* For a new container, find a cgroup path which is unique in all cgroup mounts.
* I.e. if r1 is already running, then /lxc/r1-1 may be used.
*
* @lxcgroup: the cgroup 'group' the contaienr should run in. By default, this
* is just 'lxc'. Admins may wish to group some containers into other groups,
* i.e. 'build', to take advantage of cgroup hierarchy to simplify group
* administration. Also, unprivileged users who are placed into a cgroup by
* libcgroup_pam will be using that cgroup rather than the system-wide 'lxc'
* group.
* @name: the name of the container
*
* The chosen cgpath is returned as a strdup'd string. The caller will have to
* free that eventually, however the lxc monitor will keep that string so as to
* return it in response to a LXC_COMMAND_CGROUP query.
*
* Note the path is relative to cgroup mounts. I.e. if the freezer subsystem
* is at /sys/fs/cgroup/freezer, and this fn returns '/lxc/r1', then the
* freezer cgroup's full path will be /sys/fs/cgroup/freezer/lxc/r1/.
*
* XXX This should probably be locked globally
*
* Races won't be determintal, you'll just end up with leftover unused cgroups
*/
char *lxc_cgroup_path_create(const char *lxcgroup, const char *name)
{
int i = 0, ret;
char *retpath, path[MAXPATHLEN];
char tail[12];
FILE *file = NULL;
struct mntent *mntent;
if (create_lxcgroups(lxcgroup) < 0)
return NULL;
again:
file = setmntent(MTAB, "r");
if (!file) {
SYSERROR("failed to open %s", MTAB);
return NULL;
}
if (i)
snprintf(tail, 12, "-%d", i);
else
*tail = '\0';
while ((mntent = getmntent(file))) {
if (strcmp(mntent->mnt_type, "cgroup"))
continue;
if (!mount_has_subsystem(mntent))
continue;
/* find unused mnt_dir + lxcgroup + name + -$i */
ret = snprintf(path, MAXPATHLEN, "%s/%s/%s%s", mntent->mnt_dir,
lxcgroup ? lxcgroup : "lxc", name, tail);
if (ret < 0 || ret >= MAXPATHLEN)
goto fail;
if (access(path, F_OK) == 0) goto next;
if (mkdir(path, 0755)) {
ERROR("Error creating cgroups");
goto fail;
}
}
endmntent(file);
// print out the cgpath part
ret = snprintf(path, MAXPATHLEN, "%s/%s%s",
lxcgroup ? lxcgroup : "lxc", name, tail);
if (ret < 0 || ret >= MAXPATHLEN) // can't happen
goto fail;
retpath = strdup(path);
return retpath;
next:
endmntent(file);
i++;
goto again;
fail:
endmntent(file);
return NULL;
}
