snapshot: implement snapshot unit logic

device.c

@@ -451,6 +451,7 @@ const UnitVTable device_vtable = {
 
         .no_requires = true,
         .no_instances = true,
+        .no_snapshots = true,
 
         .init = device_init,
         .load = unit_load_fragment_and_dropin_optional,

manager.h

@@ -190,6 +190,9 @@ struct Manager {
 
         /* Data specific to the Automount subsystem */
         int dev_autofs_fd;
+
+        /* Data specific to the Snapshot subsystem */
+        unsigned n_snapshots;
 };
 
 int manager_new(ManagerRunningAs running_as, bool confirm_spawn, Manager **m);

snapshot.c

@@ -19,25 +19,176 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <errno.h>
+
 #include "unit.h"
 #include "snapshot.h"
+#include "unit-name.h"
+#include "dbus-snapshot.h"
 
-static void snapshot_done(Unit *u) {
+static const UnitActiveState state_translation_table[_SNAPSHOT_STATE_MAX] = {
+        [SNAPSHOT_DEAD] = UNIT_INACTIVE,
+        [SNAPSHOT_ACTIVE] = UNIT_ACTIVE
+};
+
+static const char* const state_string_table[_SNAPSHOT_STATE_MAX] = {
+        [SNAPSHOT_DEAD] = "dead",
+        [SNAPSHOT_ACTIVE] = "active"
+};
+
+static int snapshot_load(Unit *u) {
+        Iterator i;
+        Unit *other;
+        int r;
+
+        assert(u);
+
+        HASHMAP_FOREACH(other, u->meta.manager->units, i) {
+
+                if (UNIT_VTABLE(other)->no_snapshots)
+                        continue;
+
+                if ((r = unit_add_dependency(u, UNIT_REQUIRES, other)) < 0)
+                        return r;
+
+                if ((r = unit_add_dependency(u, UNIT_AFTER, other)) < 0)
+                        return r;
+        }
+
+        u->meta.load_state = UNIT_LOADED;
+
+        return 0;
+}
+
+static void snapshot_dump(Unit *u, FILE *f, const char *prefix) {
         Snapshot *s = SNAPSHOT(u);
 
         assert(s);
+        assert(f);
 
-        /* Nothing here for now */
+        fprintf(f,
+                "%sSnapshot State: %s\n"
+                "%sClean Up: %s\n",
+                prefix, state_string_table[s->state],
+                prefix, yes_no(s->cleanup));
+}
+
+static void snapshot_set_state(Snapshot *s, SnapshotState state) {
+        SnapshotState old_state;
+        assert(s);
+
+        old_state = s->state;
+        s->state = state;
+
+        if (state != old_state)
+                log_debug("%s changed %s → %s", UNIT(s)->meta.id, state_string_table[old_state], state_string_table[state]);
+
+        unit_notify(UNIT(s), state_translation_table[old_state], state_translation_table[state]);
+}
+
+static int snapshot_start(Unit *u) {
+        Snapshot *s = SNAPSHOT(u);
+
+        assert(s);
+        assert(s->state == SNAPSHOT_DEAD);
+
+        snapshot_set_state(s, SNAPSHOT_ACTIVE);
+
+        if (s->cleanup)
+                unit_add_to_cleanup_queue(u);
+
+        return 0;
+}
+
+static int snapshot_stop(Unit *u) {
+        Snapshot *s = SNAPSHOT(u);
+
+        assert(s);
+        assert(s->state == SNAPSHOT_ACTIVE);
+
+        snapshot_set_state(s, SNAPSHOT_DEAD);
+        return 0;
 }
 
 static UnitActiveState snapshot_active_state(Unit *u) {
-        return SNAPSHOT(u)->state == SNAPSHOT_DEAD ? UNIT_INACTIVE : UNIT_ACTIVE;
+        assert(u);
+
+        return state_translation_table[SNAPSHOT(u)->state];
+}
+
+static const char *snapshot_sub_state_to_string(Unit *u) {
+        assert(u);
+
+        return state_string_table[SNAPSHOT(u)->state];
+}
+
+int snapshot_create(Manager *m, const char *name, bool cleanup, Snapshot **_s) {
+        Unit *u;
+        char *n = NULL;
+        int r;
+
+        assert(m);
+        assert(_s);
+
+        if (name) {
+                if (!unit_name_is_valid(name))
+                        return -EINVAL;
+
+                if (unit_name_to_type(name) != UNIT_SNAPSHOT)
+                        return -EINVAL;
+
+                if (manager_get_unit(m, name))
+                        return -EEXIST;
+
+        } else {
+
+                for (;;) {
+                        if (asprintf(&n, "snapshot-%u.snapshot", ++ m->n_snapshots) < 0)
+                                return -ENOMEM;
+
+                        if (!manager_get_unit(m, n))
+                                break;
+
+                        free(n);
+                }
+
+                name = n;
+        }
+
+        r = manager_load_unit(m, name, NULL, &u);
+        free(n);
+
+        if (r < 0)
+                return r;
+
+        SNAPSHOT(u)->cleanup = cleanup;
+        *_s = SNAPSHOT(u);
+
+        return 0;
+}
+
+void snapshot_remove(Snapshot *s) {
+        assert(s);
+
+        unit_add_to_cleanup_queue(UNIT(s));
 }
 
 const UnitVTable snapshot_vtable = {
         .suffix = ".snapshot",
 
-        .done = snapshot_done,
+        .no_alias = true,
+        .no_instances = true,
+        .no_snapshots = true,
 
-        .active_state = snapshot_active_state
+        .load = snapshot_load,
+
+        .dump = snapshot_dump,
+
+        .start = snapshot_start,
+        .stop = snapshot_stop,
+
+        .active_state = snapshot_active_state,
+        .sub_state_to_string = snapshot_sub_state_to_string,
+
+        .bus_message_handler = bus_snapshot_message_handler
 };

snapshot.h

@@ -28,16 +28,22 @@ typedef struct Snapshot Snapshot;
 
 typedef enum SnapshotState {
         SNAPSHOT_DEAD,
-        SNAPSHOT_ACTIVE
+        SNAPSHOT_ACTIVE,
+        _SNAPSHOT_STATE_MAX,
+        _SNAPSHOT_STATE_INVALID = -1
 } SnapshotState;
 
 struct Snapshot {
         Meta meta;
 
         SnapshotState state;
-        bool cleanup:1;
+
+        bool cleanup;
 };
 
 extern const UnitVTable snapshot_vtable;
 
+int snapshot_create(Manager *m, const char *name, bool cleanup, Snapshot **s);
+void snapshot_remove(Snapshot *s);
+
 #endif

systemctl.vala

@@ -83,7 +83,9 @@ int main (string[] args) {
                         "  stop [NAME...]      Stop on or more units\n" +
                         "  restart [NAME...]   Restart on or more units\n" +
                         "  reload [NAME...]    Reload on or more units\n" +
-                        "  monitor             Monitor unit/job changes\n");
+                        "  monitor             Monitor unit/job changes\n" +
+                        "  dump                Dump servier status\n" +
+                        "  snapshot [NAME]     Create a snapshot\n");
 
         try {
                 context.parse(ref args);
@@ -224,7 +226,17 @@ int main (string[] args) {
 
                 } else if (args[1] == "dump")
                         stdout.puts(manager.dump());
-                else {
+                else if (args[1] == "snapshot") {
+
+                        ObjectPath p = manager.create_snapshot(args.length > 2 ? args[2] : "");
+
+                        Unit u = bus.get_object(
+                                        "org.freedesktop.systemd1",
+                                        p,
+                                        "org.freedesktop.systemd1.Unit") as Unit;
+
+                        stdout.printf("%s\n", u.id);
+                } else {
                         stderr.printf("Unknown command %s.\n", args[1]);
                         return 1;
                 }

systemd-interfaces.vala

@@ -57,6 +57,8 @@ public interface Manager : DBus.Object {
 
         public abstract string dump() throws DBus.Error;
 
+        public abstract ObjectPath create_snapshot(string name, bool cleanup = false) throws DBus.Error;
+
         public abstract signal void unit_new(string id, ObjectPath path);
         public abstract signal void unit_removed(string id, ObjectPath path);
         public abstract signal void job_new(uint32 id, ObjectPath path);

unit.h

@@ -59,8 +59,8 @@ enum UnitType {
         UNIT_DEVICE,
         UNIT_MOUNT,
         UNIT_AUTOMOUNT,
-        UNIT_TIMER,
         UNIT_SNAPSHOT,
+        UNIT_TIMER,
         _UNIT_TYPE_MAX,
         _UNIT_TYPE_INVALID = -1
 };
@@ -209,6 +209,9 @@ struct UnitVTable {
         /* Instances make no sense for this type */
         bool no_instances:1;
 
+        /* Execlude this type from snapshots */
+        bool no_snapshots:1;
+
         /* This should reset all type-specific variables. This should
          * not allocate memory, and is either called with 0
          * initialized data, or with data left from done() */