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, 50 insertions, 0 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;
+}