core: add new .slice unit type for partitioning systems

In order to prepare for the kernel cgroup rework, let's introduce a new
unit type to systemd, the "slice". Slices can be arranged in a tree and
are useful to partition resources freely and hierarchally by the user.

Each service unit can now be assigned to one of these slices, and later
on login users and machines may too.

Slices translate pretty directly to the cgroup hierarchy, and the
various objects can be assigned to any of the slices in the tree.

1 files changed, 298 insertions, 0 deletions

diff --git a/src/core/slice.c b/src/core/slice.c
new file mode 100644
index 0000000000..c1c33fe5c6
--- /dev/null
+++ b/src/core/slice.c
@@ -0,0 +1,298 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "unit.h"
+#include "slice.h"
+#include "load-fragment.h"
+#include "log.h"
+#include "dbus-slice.h"
+#include "special.h"
+#include "unit-name.h"
+
+static const UnitActiveState state_translation_table[_SLICE_STATE_MAX] = {
+        [SLICE_DEAD] = UNIT_INACTIVE,
+        [SLICE_ACTIVE] = UNIT_ACTIVE
+};
+
+static void slice_set_state(Slice *t, SliceState state) {
+        SliceState old_state;
+        assert(t);
+
+        old_state = t->state;
+        t->state = state;
+
+        if (state != old_state)
+                log_debug("%s changed %s -> %s",
+                          UNIT(t)->id,
+                          slice_state_to_string(old_state),
+                          slice_state_to_string(state));
+
+        unit_notify(UNIT(t), state_translation_table[old_state], state_translation_table[state], true);
+}
+
+static int slice_add_slice_link(Slice *s) {
+        char *a, *dash;
+        int r;
+        Unit *parent;
+
+        assert(s);
+
+        if (UNIT_DEREF(UNIT(s)->slice))
+                return 0;
+
+        a = strdupa(UNIT(s)->id);
+
+        dash = strrchr(a, '-');
+        if (!dash)
+                return 0;
+
+        strcpy(dash, ".slice");
+
+        r = manager_load_unit(UNIT(s)->manager, a, NULL, NULL, &parent);
+        if (r < 0)
+                return r;
+
+        unit_ref_set(&UNIT(s)->slice, parent);
+        return 0;
+}
+
+static int slice_add_default_dependencies(Slice *s) {
+        int r;
+
+        assert(s);
+
+        /* Make sure slices are unloaded on shutdown */
+        r = unit_add_dependency_by_name(UNIT(s), UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, NULL, true);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int slice_verify(Slice *s) {
+        assert(s);
+
+        if (UNIT(s)->load_state != UNIT_LOADED)
+                return 0;
+
+        if (UNIT_DEREF(UNIT(s)->slice)) {
+                char *a, *dash;
+
+                a = strdupa(UNIT(s)->id);
+                dash = strrchr(a, '-');
+                if (dash) {
+                        strcpy(dash, ".slice");
+
+                        if (!unit_has_name(UNIT_DEREF(UNIT(s)->slice), a)) {
+                                log_error_unit(UNIT(s)->id,
+                                               "%s located outside its parent slice. Refusing.", UNIT(s)->id);
+                                return -EINVAL;
+                        }
+                }
+        }
+
+        return 0;
+}
+
+static int slice_load(Unit *u) {
+        Slice *s = SLICE(u);
+        int r;
+
+        assert(s);
+
+        r = unit_load_fragment_and_dropin(u);
+        if (r < 0)
+                return r;
+
+        /* This is a new unit? Then let's add in some extras */
+        if (u->load_state == UNIT_LOADED) {
+
+                r = slice_add_slice_link(s);
+                if (r < 0)
+                        return r;
+
+                if (u->default_dependencies) {
+                        r = slice_add_default_dependencies(s);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = unit_add_default_cgroups(UNIT(s));
+                if (r < 0)
+                        return r;
+        }
+
+        return slice_verify(s);
+}
+
+static int slice_coldplug(Unit *u) {
+        Slice *t = SLICE(u);
+
+        assert(t);
+        assert(t->state == SLICE_DEAD);
+
+        if (t->deserialized_state != t->state)
+                slice_set_state(t, t->deserialized_state);
+
+        return 0;
+}
+
+static void slice_dump(Unit *u, FILE *f, const char *prefix) {
+        Slice *t = SLICE(u);
+
+        assert(t);
+        assert(f);
+
+        fprintf(f,
+                "%sSlice State: %s\n",
+                prefix, slice_state_to_string(t->state));
+}
+
+static int slice_start(Unit *u) {
+        Slice *t = SLICE(u);
+        int r;
+
+        assert(t);
+        assert(t->state == SLICE_DEAD);
+
+        r = cgroup_bonding_realize_list(u->cgroup_bondings);
+        if (r < 0)
+                return r;
+
+        cgroup_attribute_apply_list(u->cgroup_attributes, u->cgroup_bondings);
+
+        slice_set_state(t, SLICE_ACTIVE);
+        return 0;
+}
+
+static int slice_stop(Unit *u) {
+        Slice *t = SLICE(u);
+
+        assert(t);
+        assert(t->state == SLICE_ACTIVE);
+
+        /* We do not need to trim the cgroup explicitly, unit_notify()
+         * will do that for us anyway. */
+
+        slice_set_state(t, SLICE_DEAD);
+        return 0;
+}
+
+static int slice_kill(Unit *u, KillWho who, int signo, DBusError *error) {
+        return unit_kill_common(u, who, signo, -1, -1, error);
+}
+
+static int slice_serialize(Unit *u, FILE *f, FDSet *fds) {
+        Slice *s = SLICE(u);
+
+        assert(s);
+        assert(f);
+        assert(fds);
+
+        unit_serialize_item(u, f, "state", slice_state_to_string(s->state));
+        return 0;
+}
+
+static int slice_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {
+        Slice *s = SLICE(u);
+
+        assert(u);
+        assert(key);
+        assert(value);
+        assert(fds);
+
+        if (streq(key, "state")) {
+                SliceState state;
+
+                state = slice_state_from_string(value);
+                if (state < 0)
+                        log_debug("Failed to parse state value %s", value);
+                else
+                        s->deserialized_state = state;
+
+        } else
+                log_debug("Unknown serialization key '%s'", key);
+
+        return 0;
+}
+
+_pure_ static UnitActiveState slice_active_state(Unit *u) {
+        assert(u);
+
+        return state_translation_table[SLICE(u)->state];
+}
+
+_pure_ static const char *slice_sub_state_to_string(Unit *u) {
+        assert(u);
+
+        return slice_state_to_string(SLICE(u)->state);
+}
+
+static const char* const slice_state_table[_SLICE_STATE_MAX] = {
+        [SLICE_DEAD] = "dead",
+        [SLICE_ACTIVE] = "active"
+};
+
+DEFINE_STRING_TABLE_LOOKUP(slice_state, SliceState);
+
+const UnitVTable slice_vtable = {
+        .object_size = sizeof(Slice),
+        .sections =
+                "Unit\0"
+                "Slice\0"
+                "Install\0",
+
+        .no_alias = true,
+        .no_instances = true,
+
+        .load = slice_load,
+        .coldplug = slice_coldplug,
+
+        .dump = slice_dump,
+
+        .start = slice_start,
+        .stop = slice_stop,
+
+        .kill = slice_kill,
+
+        .serialize = slice_serialize,
+        .deserialize_item = slice_deserialize_item,
+
+        .active_state = slice_active_state,
+        .sub_state_to_string = slice_sub_state_to_string,
+
+        .bus_interface = "org.freedesktop.systemd1.Slice",
+        .bus_message_handler = bus_slice_message_handler,
+
+        .status_message_formats = {
+                .finished_start_job = {
+                        [JOB_DONE]       = "Installed slice %s.",
+                        [JOB_DEPENDENCY] = "Dependency failed for %s.",
+                },
+                .finished_stop_job = {
+                        [JOB_DONE]       = "Deinstalled slice %s.",
+                },
+        },
+};