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, 43 insertions, 0 deletions

diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index e2015ed58f..4a835b6e8b 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -2058,6 +2058,48 @@ int config_parse_syscall_filter(const char *unit,
         return 0;
 }
 
+int config_parse_unit_slice(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        _cleanup_free_ char *k = NULL;
+        Unit *u = userdata, *slice;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(u);
+
+        k = unit_name_printf(u, rvalue);
+        if (!k)
+                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+                           "Failed to resolve unit specifiers on %s. Ignoring.", rvalue);
+
+        r = manager_load_unit(u->manager, k ? k : rvalue, NULL, NULL, &slice);
+        if (r < 0) {
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to load slice unit %s. Ignoring.", k ? k : rvalue);
+                return 0;
+        }
+
+        if (slice->type != UNIT_SLICE) {
+                log_syntax(unit, LOG_ERR, filename, line, EINVAL,
+                           "Slice unit %s is not a slice. Ignoring.", k ? k : rvalue);
+                return 0;
+        }
+
+        unit_ref_set(&u->slice, slice);
+        return 0;
+}
+
 #define FOLLOW_MAX 8
 
 static int open_follow(char **filename, FILE **_f, Set *names, char **_final) {
@@ -2446,6 +2488,7 @@ void unit_dump_config_items(FILE *f) {
                 { config_parse_unit_condition_path,   "CONDITION" },
                 { config_parse_unit_condition_string, "CONDITION" },
                 { config_parse_unit_condition_null,   "CONDITION" },
+                { config_parse_unit_slice,            "SLICE" },
         };
 
         const char *prev = NULL;