Ignore trailing /init.scope in init cgroups

The lxc monitor does not store the container's cgroups, rather it
recalculates them whenever needed.

Systemd moves itself into a /init.scope cgroup for the systemd
controller.

It might be worth changing that (by storing all cgroup info in the
lxc_handler), but for now go the hacky route and chop off any
trailing /init.scope.

I definately thinkg we want to switch to storing as that will be
more bullet-proof, but for now we need a quick backportable fix
for systemd 226 guests.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>

src/lxc/cgfs.c

@@ -1220,6 +1220,7 @@ static char *lxc_cgroup_get_hierarchy_path_data(const char *subsystem, struct cg
 	info = find_info_for_subsystem(info, subsystem);
 	if (!info)
 		return NULL;
+	prune_init_scope(info->cgroup_path);
 	return info->cgroup_path;
 }
 

src/lxc/cgmanager.c

@@ -776,6 +776,7 @@ static char *try_get_abs_cgroup(const char *name, const char *lxcpath,
 			nerr = nih_error_get();
 			nih_free(nerr);
 		}
+		prune_init_scope(cgroup);
 		return cgroup;
 	}
 

src/lxc/cgroup.c

@@ -194,3 +194,17 @@ cgroup_driver_t cgroup_driver(void)
 {
 	return ops->driver;
 }
+
+#define INIT_SCOPE "/init.scope"
+void prune_init_scope(char *cg)
+{
+	char *point = cg + strlen(cg) - strlen(INIT_SCOPE);
+	if (point < cg)
+		return;
+	if (strcmp(point, INIT_SCOPE) == 0) {
+		if (point == cg)
+			*(point+1) = '\0';
+		else
+			*point = '\0';
+	}
+}

src/lxc/cgroup.h

@@ -80,4 +80,6 @@ extern bool cgroup_unfreeze(struct lxc_handler *handler);
 extern void cgroup_disconnect(void);
 extern cgroup_driver_t cgroup_driver(void);
 
+extern void prune_init_scope(char *cg);
+
 #endif