logind: add infrastructure to keep track of machines, and move to slices

- This changes all logind cgroup objects to use slice objects rather
  than fixed croup locations.

- logind can now collect minimal information about running
  VMs/containers. As fixed cgroup locations can no longer be used we
  need an entity that keeps track of machine cgroups in whatever slice
  they might be located. Since logind already keeps track of users,
  sessions and seats this is a trivial addition.

- nspawn will now register with logind and pass various bits of metadata
  along. A new option "--slice=" has been added to place the container
  in a specific slice.

- loginctl gained commands to list, introspect and terminate machines.

- user.slice and machine.slice will now be pulled in by logind.service,
  since only logind.service requires this slice.

1 files changed, 106 insertions, 15 deletions

diff --git a/src/login/user-sessions.c b/src/login/user-sessions.c
index 41d32044e9..18066ccc39 100644
--- a/src/login/user-sessions.c
+++ b/src/login/user-sessions.c
@@ -28,6 +28,106 @@
 #include "cgroup-util.h"
 #include "fileio.h"
 
+static int kill_all_users(void) {
+        _cleanup_closedir_ DIR *d = NULL;
+        struct dirent *de;
+        int r = 0;
+
+        d = opendir("/run/systemd/users");
+        if (!d) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_error("Failed to open /run/systemd/users: %m");
+                return -errno;
+        }
+
+        FOREACH_DIRENT(de, d, return -errno) {
+                _cleanup_free_ char *cgroup = NULL;
+                char *a;
+                int k;
+
+                if (!dirent_is_file(de))
+                        continue;
+
+                a = strappenda("/run/systemd/users/", de->d_name);
+
+                k = parse_env_file(a, NEWLINE, "CGROUP", &cgroup, NULL);
+                if (k < 0) {
+                        if (k != -ENOENT) {
+                                log_error("Failed to read user data: %s", strerror(-k));
+                                r = k;
+                        }
+
+                        continue;
+                }
+
+                if (!cgroup) {
+                        log_error("User data did not contain cgroup field.");
+                        r = -ENOENT;
+                        continue;
+                }
+
+                k = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, cgroup, true);
+                if (k < 0) {
+                        log_error("Failed to kill cgroup %s: %s", cgroup, strerror(-k));
+                        r = k;
+                }
+        }
+
+        return r;
+}
+
+static int kill_all_sessions(void) {
+        _cleanup_closedir_ DIR *d = NULL;
+        struct dirent *de;
+        int r = 0;
+
+        d = opendir("/run/systemd/sessions");
+        if (!d) {
+                if (errno == ENOENT)
+                        return 0;
+
+                log_error("Failed to open /run/systemd/sessions: %m");
+                return -errno;
+        }
+
+        FOREACH_DIRENT(de, d, return -errno) {
+                _cleanup_free_ char *cgroup = NULL;
+                char *a;
+                int k;
+
+                if (!dirent_is_file(de))
+                        continue;
+
+                a = strappenda("/run/systemd/sessions/", de->d_name);
+
+                k = parse_env_file(a, NEWLINE, "CGROUP", &cgroup, NULL);
+                if (k < 0) {
+                        if (k != -ENOENT) {
+                                log_error("Failed to read session data: %s", strerror(-k));
+                                r = k;
+                        }
+
+                        continue;
+                }
+
+                if (!cgroup) {
+                        log_error("Session data did not contain cgroup field.");
+                        r = -ENOENT;
+                        continue;
+                }
+
+                k = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, cgroup, true);
+                if (k < 0) {
+                        log_error("Failed to kill cgroup %s: %s", cgroup, strerror(-k));
+                        r = k;
+                }
+        }
+
+        return r;
+}
+
 int main(int argc, char*argv[]) {
         int ret = EXIT_FAILURE;
 
@@ -68,27 +168,18 @@ int main(int argc, char*argv[]) {
 
         } else if (streq(argv[1], "stop")) {
                 int r, q;
-                char *cgroup_user_tree = NULL;
 
                 r = write_string_file_atomic("/run/nologin", "System is going down.");
                 if (r < 0)
                         log_error("Failed to create /run/nologin: %s", strerror(-r));
 
-                q = cg_get_user_path(&cgroup_user_tree);
-                if (q < 0) {
-                        log_error("Failed to determine use path: %s", strerror(-q));
-                        goto finish;
-                }
-
-                q = cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, cgroup_user_tree, true);
-                free(cgroup_user_tree);
-                if (q < 0) {
-                        log_error("Failed to kill sessions: %s", strerror(-q));
-                        goto finish;
-                }
+                q = kill_all_users();
+                if (q < 0 && r >= 0)
+                        r = q;
 
-                if (r < 0)
-                        goto finish;
+                q = kill_all_sessions();
+                if (q < 0 && r >= 0)
+                        r = q;
 
         } else {
                 log_error("Unknown verb %s.", argv[1]);