utils: call MaybeMoveToSubCgroup once

memoize its result and use it for subsequent calls.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

utils/utils.go

@@ -191,22 +191,32 @@ func MovePauseProcessToScope(pausePidPath string) {
 	}
 }
 
+var (
+	maybeMoveToSubCgroupSync    sync.Once
+	maybeMoveToSubCgroupSyncErr error
+)
+
 // MaybeMoveToSubCgroup moves the current process in a sub cgroup when
 // it is running in the root cgroup on a system that uses cgroupv2.
 func MaybeMoveToSubCgroup() error {
-	unifiedMode, err := cgroups.IsCgroup2UnifiedMode()
-	if err != nil {
-		return err
-	}
-	if !unifiedMode {
-		return nil
-	}
-	cgroup, err := GetOwnCgroup()
-	if err != nil {
-		return err
-	}
-	if cgroup == "/" {
-		return MoveUnderCgroupSubtree("init")
-	}
-	return nil
+	maybeMoveToSubCgroupSync.Do(func() {
+		unifiedMode, err := cgroups.IsCgroup2UnifiedMode()
+		if err != nil {
+			maybeMoveToSubCgroupSyncErr = err
+			return
+		}
+		if !unifiedMode {
+			maybeMoveToSubCgroupSyncErr = nil
+			return
+		}
+		cgroup, err := GetOwnCgroup()
+		if err != nil {
+			maybeMoveToSubCgroupSyncErr = err
+			return
+		}
+		if cgroup == "/" {
+			maybeMoveToSubCgroupSyncErr = MoveUnderCgroupSubtree("init")
+		}
+	})
+	return maybeMoveToSubCgroupSyncErr
 }