Revert "util: vircgroup: pass parent cgroup into virCgroupDetectControllersCB"

This reverts commit 7bca1c9b.

As it turns out it's not a good idea on systemd hosts.  The root
cgroup can have all controllers enabled but they don't have to be
enabled for sub-cgroups.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/util/vircgroup.c

@@ -407,7 +407,7 @@ virCgroupDetect(virCgroupPtr group,
 
     for (i = 0; i < VIR_CGROUP_BACKEND_TYPE_LAST; i++) {
         if (group->backends[i]) {
-            int rc = group->backends[i]->detectControllers(group, controllers, parent);
+            int rc = group->backends[i]->detectControllers(group, controllers);
             if (rc < 0)
                 return -1;
             controllersAvailable |= rc;

src/util/vircgroupbackend.h

@@ -95,8 +95,7 @@ typedef char *
 
 typedef int
 (*virCgroupDetectControllersCB)(virCgroupPtr group,
-                                int controllers,
-                                virCgroupPtr parent);
+                                int controllers);
 
 typedef bool
 (*virCgroupHasControllerCB)(virCgroupPtr cgroup,

src/util/vircgroupv1.c

@@ -420,8 +420,7 @@ virCgroupV1StealPlacement(virCgroupPtr group)
 
 static int
 virCgroupV1DetectControllers(virCgroupPtr group,
-                             int controllers,
-                             virCgroupPtr parent ATTRIBUTE_UNUSED)
+                             int controllers)
 {
     size_t i;
     size_t j;

src/util/vircgroupv2.c

@@ -286,21 +286,16 @@ virCgroupV2ParseControllersFile(virCgroupPtr group)
 
 static int
 virCgroupV2DetectControllers(virCgroupPtr group,
-                             int controllers,
-                             virCgroupPtr parent)
+                             int controllers)
 {
     size_t i;
 
-    if (parent) {
-        group->unified.controllers = parent->unified.controllers;
-    } else {
-        if (virCgroupV2ParseControllersFile(group) < 0)
-            return -1;
+    if (virCgroupV2ParseControllersFile(group) < 0)
+        return -1;
 
-        /* In cgroup v2 there is no cpuacct controller, the cpu.stat file always
-         * exists with usage stats. */
-        group->unified.controllers |= 1 << VIR_CGROUP_CONTROLLER_CPUACCT;
-    }
+    /* In cgroup v2 there is no cpuacct controller, the cpu.stat file always
+     * exists with usage stats. */
+    group->unified.controllers |= 1 << VIR_CGROUP_CONTROLLER_CPUACCT;
 
     if (controllers >= 0)
         group->unified.controllers &= controllers;