nspawn: introduce the new /machine/ tree in the cgroup tree and move containers there

Containers will now carry a label (normally derived from the root
directory name, but configurable by the user), and the container's root
cgroup is /machine/<label>. This label is called "machine name", and can
cover both containers and VMs (as soon as libvirt also makes use of
/machine/).

libsystemd-login can be used to query the machine name from a process.

This patch also includes numerous clean-ups for the cgroup code.

1 files changed, 3 insertions, 6 deletions

diff --git a/src/login/logind.c b/src/login/logind.c
index aa3e5f0914..caed149ad6 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -1100,21 +1100,18 @@ int manager_get_user_by_cgroup(Manager *m, const char *cgroup, User **user) {
 }
 
 int manager_get_session_by_pid(Manager *m, pid_t pid, Session **session) {
-        char *p;
+        _cleanup_free_ char *p = NULL;
         int r;
 
         assert(m);
         assert(pid >= 1);
         assert(session);
 
-        r = cg_get_by_pid(SYSTEMD_CGROUP_CONTROLLER, pid, &p);
+        r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &p);
         if (r < 0)
                 return r;
 
-        r = manager_get_session_by_cgroup(m, p, session);
-        free(p);
-
-        return r;
+        return manager_get_session_by_cgroup(m, p, session);
 }
 
 void manager_cgroup_notify_empty(Manager *m, const char *cgroup) {