Fix kublelet killing VMs upon Virtlet pod restart

The culprit were cgroups that aren't handled by libvirt.
Of those, we already handle hugetlb by moving the emulator
process out of it. Still, need to do the same for systemd
(name=systemd) and pids cgroup controllers.

The problem manifested itself when cgroup-per-qos is enabled for
kubelet. This is the default, but in current kdc it may
be disabled as a workaround for old kubelet bug. This bug
is already fixed, so the workaround is to be removed soon.

cmd/vmwrapper/vmwrapper.go

@@ -71,13 +71,17 @@ func main() {
 		}
 	}
 
-	// FIXME: move the pid of qemu instance out of /kubepods/podxxxxxxx
-	// for some cases it will be killed by kubelet after the virtlet pod is deleted/recreated
+	// FIXME: move the pid of qemu instance out of kubelet-managed
+	// for cgroups that aren't managed by libvirt.
+	// If we don't do this, the VM pod will be killed by kubelet when Virtlet pod
+	// is removed dnd cgroup-per-qos is enabled in kubelet settings.
 	cm := cgroups.NewManager(os.Getpid(), nil)
-	if _, err := cm.GetProcessController("hugetlb"); err == nil {
-		err = cm.MoveProcess("hugetlb", "/")
-		if err != nil {
-			glog.Warningf("failed to move pid into hugetlb path /: %v", err)
+	for _, ctl := range []string{"hugetlb", "systemd", "pids"} {
+		if _, err := cm.GetProcessController(ctl); err == nil {
+			err = cm.MoveProcess(ctl, "/")
+			if err != nil {
+				glog.Warningf("failed to move pid into cgroup %q path /: %v", ctl, err)
+			}
 		}
 	}
 

pkg/utils/cgroups/controllers.go

@@ -94,8 +94,15 @@ func (c *RealManager) GetProcessControllers() (map[string]string, error) {
 		// "6:memory:/user.slice/user-xxx.slice/session-xx.scope"
 		parts := strings.SplitN(line, ":", 3)
 
+		name := parts[1]
+		if strings.HasPrefix(name, "name=") {
+			// Handle named cgroup hierarchies like name=systemd
+			// The corresponding directory tree will be /sys/fs/cgroup/systemd
+			name = name[5:]
+		}
+
 		// use second part as controller name and third as its path
-		ctrls[parts[1]] = parts[2]
+		ctrls[name] = parts[2]
 
 		if err == io.EOF {
 			break