Initialize cgroups on lxc-checkpoint -r

With cgmanager, the cgroups are polled on demand, so these steps aren't needed.
However, with cgfs, lxc doesn't know about the cgroups for a container and so
it can't report any of the statistics about e.g. how much memory or CPU a
container is using.

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

src/lxc/cgfs.c

@@ -2376,6 +2376,18 @@ static bool lxc_cgroupfs_attach(const char *name, const char *lxcpath, pid_t pid
 	return true;
 }
 
+static bool cgfs_parse_existing_cgroups(void *hdata, pid_t init)
+{
+	struct cgfs_data *d = hdata;
+
+	if (!d)
+		return false;
+
+	d->info = lxc_cgroup_process_info_get(init, d->meta);
+
+	return !!(d->info);
+}
+
 static struct cgroup_ops cgfs_ops = {
 	.init = cgfs_init,
 	.destroy = cgfs_destroy,
@@ -2390,6 +2402,7 @@ static struct cgroup_ops cgfs_ops = {
 	.name = "cgroupfs",
 	.attach = lxc_cgroupfs_attach,
 	.chown = NULL,
+	.parse_existing_cgroups = cgfs_parse_existing_cgroups,
 	.mount_cgroup = cgroupfs_mount_cgroup,
 	.nrtasks = cgfs_nrtasks,
 };

src/lxc/cgmanager.c

@@ -1313,6 +1313,7 @@ static struct cgroup_ops cgmanager_ops = {
 	.setup_limits = cgm_setup_limits,
 	.name = "cgmanager",
 	.chown = cgm_chown,
+	.parse_existing_cgroups = NULL,
 	.attach = cgm_attach,
 	.mount_cgroup = cgm_mount_cgroup,
 	.nrtasks = cgm_get_nrtasks,

src/lxc/cgroup.c

@@ -128,6 +128,15 @@ bool cgroup_chown(struct lxc_handler *handler)
 	return true;
 }
 
+bool cgroup_parse_existing_cgroups(struct lxc_handler *handler)
+{
+	if (ops && ops->parse_existing_cgroups)
+		return ops->parse_existing_cgroups(handler->cgroup_data, handler->pid);
+
+	/* cgmanager does this automatically */
+	return true;
+}
+
 bool cgroup_mount(const char *root, struct lxc_handler *handler, int type)
 {
 	if (ops) {

src/lxc/cgroup.h

@@ -46,6 +46,7 @@ struct cgroup_ops {
 	bool (*unfreeze)(void *hdata);
 	bool (*setup_limits)(void *hdata, struct lxc_list *cgroup_conf, bool with_devices);
 	bool (*chown)(void *hdata, struct lxc_conf *conf);
+	bool (*parse_existing_cgroups)(void *hdata, pid_t pid);
 	bool (*attach)(const char *name, const char *lxcpath, pid_t pid);
 	bool (*mount_cgroup)(void *hdata, const char *root, int type);
 	int (*nrtasks)(void *hdata);
@@ -59,6 +60,7 @@ extern bool cgroup_init(struct lxc_handler *handler);
 extern bool cgroup_create(struct lxc_handler *handler);
 extern bool cgroup_setup_limits(struct lxc_handler *handler, bool with_devices);
 extern bool cgroup_chown(struct lxc_handler *handler);
+extern bool cgroup_parse_existing_cgroups(struct lxc_handler *handler);
 extern bool cgroup_enter(struct lxc_handler *handler);
 extern void cgroup_cleanup(struct lxc_handler *handler);
 extern bool cgroup_create_legacy(struct lxc_handler *handler);

src/lxc/lxccontainer.c

@@ -3895,6 +3895,17 @@ static bool lxcapi_restore(struct lxc_container *c, char *directory, bool verbos
 					goto out_fini_handler;
 				}
 
+				if (!cgroup_init(handler)) {
+					error = true;
+					ERROR("failed initing cgroups");
+					goto out_fini_handler;
+				}
+
+				if (!cgroup_parse_existing_cgroups(handler)) {
+					ERROR("failed creating cgroups");
+					goto out_fini_handler;
+				}
+
 				if (container_mem_lock(c)) {
 					error = true;
 					goto out_fini_handler;