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, 15 insertions, 9 deletions

diff --git a/src/core/unit.h b/src/core/unit.h
index b04475e4fb..81b8adbfdc 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -118,6 +118,15 @@ enum UnitDependency {
 #include "cgroup.h"
 #include "cgroup-attr.h"
 
+struct UnitRef {
+        /* Keeps tracks of references to a unit. This is useful so
+         * that we can merge two units if necessary and correct all
+         * references to them */
+
+        Unit* unit;
+        LIST_FIELDS(UnitRef, refs);
+};
+
 struct Unit {
         Manager *manager;
 
@@ -168,6 +177,8 @@ struct Unit {
         CGroupBonding *cgroup_bondings;
         CGroupAttribute *cgroup_attributes;
 
+        UnitRef slice;
+
         /* Per type list */
         LIST_FIELDS(Unit, units_by_type);
 
@@ -240,15 +251,6 @@ struct Unit {
         bool in_audit:1;
 };
 
-struct UnitRef {
-        /* Keeps tracks of references to a unit. This is useful so
-         * that we can merge two units if necessary and correct all
-         * references to them */
-
-        Unit* unit;
-        LIST_FIELDS(UnitRef, refs);
-};
-
 struct UnitStatusMessageFormats {
         const char *starting_stopping[2];
         const char *finished_start_job[_JOB_RESULT_MAX];
@@ -265,6 +267,7 @@ struct UnitStatusMessageFormats {
 #include "snapshot.h"
 #include "swap.h"
 #include "path.h"
+#include "slice.h"
 
 struct UnitVTable {
         /* How much memory does an object of this unit type need */
@@ -433,6 +436,7 @@ DEFINE_CAST(AUTOMOUNT, Automount);
 DEFINE_CAST(SNAPSHOT, Snapshot);
 DEFINE_CAST(SWAP, Swap);
 DEFINE_CAST(PATH, Path);
+DEFINE_CAST(SLICE, Slice);
 
 Unit *unit_new(Manager *m, size_t size);
 void unit_free(Unit *u);
@@ -474,6 +478,8 @@ int unit_load_fragment_and_dropin(Unit *u);
 int unit_load_fragment_and_dropin_optional(Unit *u);
 int unit_load(Unit *unit);
 
+int unit_add_default_slice(Unit *u);
+
 const char *unit_description(Unit *u) _pure_;
 
 bool unit_has_name(Unit *u, const char *name);