machined: rework referencing of machine scopes from machined, too

When a machine scope is registered by machined, let's add a reference to
it, and change the GC mode so that the unit is cleaned up as soon as
machined drops the reference, regardless of the fail state.

Fixes: #2809

3 files changed, 38 insertions, 13 deletions

diff --git a/src/machine/machine.c b/src/machine/machine.c
index 239228b2d2..d5e0d4953f 100644
--- a/src/machine/machine.c
+++ b/src/machine/machine.c
@@ -403,7 +403,7 @@ int machine_start(Machine *m, sd_bus_message *properties, sd_bus_error *error) {
 static int machine_stop_scope(Machine *m) {
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
         char *job = NULL;
-        int r;
+        int r, q;
 
         assert(m);
         assert(m->class != MACHINE_HOST);
@@ -412,10 +412,17 @@ static int machine_stop_scope(Machine *m) {
                 return 0;
 
         r = manager_stop_unit(m->manager, m->unit, &error, &job);
-        if (r < 0)
-                return log_error_errno(r, "Failed to stop machine scope: %s", bus_error_message(&error, r));
+        if (r < 0) {
+                log_error_errno(r, "Failed to stop machine scope: %s", bus_error_message(&error, r));
+                sd_bus_error_free(&error);
+        } else
+                free_and_replace(m->scope_job, job);
+
+        q = manager_unref_unit(m->manager, m->unit, &error);
+        if (q < 0)
+                log_warning_errno(q, "Failed to drop reference to machine scope, ignoring: %s", bus_error_message(&error, r));
 
-        return free_and_replace(m->scope_job, job);
+        return r;
 }
 
 int machine_stop(Machine *m) {
diff --git a/src/machine/machined-dbus.c b/src/machine/machined-dbus.c
index 32c0b04283..87e6298c78 100644
--- a/src/machine/machined-dbus.c
+++ b/src/machine/machined-dbus.c
@@ -1363,18 +1363,15 @@ int manager_start_scope(
                         return r;
         }
 
-        r = sd_bus_message_append(m, "(sv)", "PIDs", "au", 1, pid);
+        r = sd_bus_message_append(m, "(sv)(sv)(sv)(sv)(sv)",
+                                  "PIDs", "au", 1, pid,
+                                  "Delegate", "b", 1,
+                                  "CollectMode", "s", "inactive-or-failed",
+                                  "AddRef", "b", 1,
+                                  "TasksMax", "t", UINT64_C(16384));
         if (r < 0)
                 return r;
 
-        r = sd_bus_message_append(m, "(sv)", "Delegate", "b", 1);
-        if (r < 0)
-                return r;
-
-        r = sd_bus_message_append(m, "(sv)", "TasksMax", "t", UINT64_C(16384));
-        if (r < 0)
-                return bus_log_create_error(r);
-
         if (more_properties) {
                 r = sd_bus_message_copy(m, more_properties, true);
                 if (r < 0)
@@ -1411,6 +1408,26 @@ int manager_start_scope(
         return 1;
 }
 
+int manager_unref_unit(
+                Manager *m,
+                const char *unit,
+                sd_bus_error *error) {
+
+        assert(m);
+        assert(unit);
+
+        return sd_bus_call_method(
+                        m->bus,
+                        "org.freedesktop.systemd1",
+                        "/org/freedesktop/systemd1",
+                        "org.freedesktop.systemd1.Manager",
+                        "UnrefUnit",
+                        error,
+                        NULL,
+                        "s",
+                        unit);
+}
+
 int manager_stop_unit(Manager *manager, const char *unit, sd_bus_error *error, char **job) {
         _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
         int r;
diff --git a/src/machine/machined.h b/src/machine/machined.h
index 3197c1aade..ef63f96e97 100644
--- a/src/machine/machined.h
+++ b/src/machine/machined.h
@@ -50,5 +50,6 @@ int match_job_removed(sd_bus_message *message, void *userdata, sd_bus_error *err
 int manager_start_scope(Manager *manager, const char *scope, pid_t pid, const char *slice, const char *description, sd_bus_message *more_properties, sd_bus_error *error, char **job);
 int manager_stop_unit(Manager *manager, const char *unit, sd_bus_error *error, char **job);
 int manager_kill_unit(Manager *manager, const char *unit, int signo, sd_bus_error *error);
+int manager_unref_unit(Manager *m, const char *unit, sd_bus_error *error);
 int manager_unit_is_active(Manager *manager, const char *unit);
 int manager_job_is_active(Manager *manager, const char *path);