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.

4 files changed, 62 insertions, 5 deletions

diff --git a/src/shared/cgroup-util.c b/src/shared/cgroup-util.c
index 7af0c3c124..4f58affe38 100644
--- a/src/shared/cgroup-util.c
+++ b/src/shared/cgroup-util.c
@@ -1617,3 +1617,53 @@ bool cg_controller_is_valid(const char *p, bool allow_named) {
 
         return true;
 }
+
+int cg_slice_to_path(const char *unit, char **ret) {
+        _cleanup_free_ char *p = NULL, *s = NULL, *e = NULL;
+        const char *dash;
+
+        assert(unit);
+        assert(ret);
+
+        if (!unit_name_is_valid(unit, false))
+                return -EINVAL;
+
+        if (!endswith(unit, ".slice"))
+                return -EINVAL;
+
+        p = unit_name_to_prefix(unit);
+        if (!p)
+                return -ENOMEM;
+
+        dash = strchr(p, '-');
+        while (dash) {
+                _cleanup_free_ char *escaped = NULL;
+                char n[dash - p + sizeof(".slice")];
+
+                strcpy(stpncpy(n, p, dash - p), ".slice");
+
+                if (!unit_name_is_valid(n, false))
+                        return -EINVAL;
+
+                escaped = cg_escape(n);
+                if (!escaped)
+                        return -ENOMEM;
+
+                if (!strextend(&s, escaped, "/", NULL))
+                        return -ENOMEM;
+
+                dash = strchr(dash+1, '-');
+        }
+
+        e = cg_escape(unit);
+        if (!e)
+                return -ENOMEM;
+
+        if (!strextend(&s, e, NULL))
+                return -ENOMEM;
+
+        *ret = s;
+        s = NULL;
+
+        return 0;
+}
diff --git a/src/shared/cgroup-util.h b/src/shared/cgroup-util.h
index 5835e04075..84274e605d 100644
--- a/src/shared/cgroup-util.h
+++ b/src/shared/cgroup-util.h
@@ -112,3 +112,5 @@ char *cg_escape(const char *p);
 char *cg_unescape(const char *p) _pure_;
 
 bool cg_controller_is_valid(const char *p, bool allow_named);
+
+int cg_slice_to_path(const char *unit, char **ret);
diff --git a/src/shared/unit-name.c b/src/shared/unit-name.c
index a809713595..2d4cd8d9f3 100644
--- a/src/shared/unit-name.c
+++ b/src/shared/unit-name.c
@@ -44,6 +44,7 @@ static const char* const unit_type_table[_UNIT_TYPE_MAX] = {
         [UNIT_TIMER] = "timer",
         [UNIT_SWAP] = "swap",
         [UNIT_PATH] = "path",
+        [UNIT_SLICE] = "slice"
 };
 
 DEFINE_STRING_TABLE_LOOKUP(unit_type, UnitType);
@@ -184,6 +185,7 @@ char *unit_name_change_suffix(const char *n, const char *suffix) {
         assert(n);
         assert(unit_name_is_valid(n, true));
         assert(suffix);
+        assert(suffix[0] == '.');
 
         assert_se(e = strrchr(n, '.'));
         a = e - n;
@@ -506,16 +508,18 @@ char *unit_name_mangle(const char *name) {
         return r;
 }
 
-char *snapshot_name_mangle(const char *name) {
+char *unit_name_mangle_with_suffix(const char *name, const char *suffix) {
         char *r, *t;
         const char *f;
 
         assert(name);
+        assert(suffix);
+        assert(suffix[0] == '.');
 
         /* Similar to unit_name_mangle(), but is called when we know
          * that this is about snapshot units. */
 
-        r = new(char, strlen(name) * 4 + 1 + sizeof(".snapshot")-1);
+        r = new(char, strlen(name) * 4 + strlen(suffix) + 1);
         if (!r)
                 return NULL;
 
@@ -528,8 +532,8 @@ char *snapshot_name_mangle(const char *name) {
                         *(t++) = *f;
         }
 
-        if (!endswith(name, ".snapshot"))
-                strcpy(t, ".snapshot");
+        if (!endswith(name, suffix))
+                strcpy(t, suffix);
         else
                 *t = 0;
 
diff --git a/src/shared/unit-name.h b/src/shared/unit-name.h
index 9eca8eb3c1..baa487a81d 100644
--- a/src/shared/unit-name.h
+++ b/src/shared/unit-name.h
@@ -41,6 +41,7 @@ enum UnitType {
         UNIT_TIMER,
         UNIT_SWAP,
         UNIT_PATH,
+        UNIT_SLICE,
         _UNIT_TYPE_MAX,
         _UNIT_TYPE_INVALID = -1
 };
@@ -94,4 +95,4 @@ char *unit_name_to_path(const char *name);
 char *unit_dbus_path_from_name(const char *name);
 
 char *unit_name_mangle(const char *name);
-char *snapshot_name_mangle(const char *name);
+char *unit_name_mangle_with_suffix(const char *name, const char *suffix);