Choose default-cgroup parent by cgroup driver

It's "/docker" for cgroupfs and "system.slice" for systemd.

Fix #19140

Signed-off-by: Alexander Morozov <lk4d4@docker.com>
Upstream-commit: c1cd45d547ef26cf988dc72d456430361dafcf08
Component: engine

components/engine/daemon/execdriver/driver_unix.go

@@ -146,14 +146,11 @@ func InitContainer(c *Command) *configs.Config {
 	// This can be overridden later by driver during mount setup based
 	// on volume options
 	SetRootPropagation(container, mount.RPRIVATE)
+	container.Cgroups.Parent = c.CgroupParent
 
 	// check to see if we are running in ramdisk to disable pivot root
 	container.NoPivotRoot = os.Getenv("DOCKER_RAMDISK") != ""
 
-	// Default parent cgroup is "docker". Override if required.
-	if c.CgroupParent != "" {
-		container.Cgroups.Parent = c.CgroupParent
-	}
 	return container
 }
 

components/engine/daemon/execdriver/native/driver.go

@@ -16,7 +16,6 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/daemon/execdriver"
-	"github.com/docker/docker/daemon/execdriver/native/template"
 	"github.com/docker/docker/pkg/parsers"
 	"github.com/docker/docker/pkg/pools"
 	"github.com/docker/docker/pkg/reexec"
@@ -90,7 +89,6 @@ func NewDriver(root string, options []string) (*Driver, error) {
 			case "systemd":
 				if systemd.UseSystemd() {
 					cgm = libcontainer.SystemdCgroups
-					template.SystemdCgroups = true
 				} else {
 					// warn them that they chose the wrong driver
 					logrus.Warn("You cannot use systemd as native.cgroupdriver, using cgroupfs instead")

components/engine/daemon/execdriver/native/template/default_template_linux.go

@@ -9,9 +9,6 @@ import (
 
 const defaultMountFlags = syscall.MS_NOEXEC | syscall.MS_NOSUID | syscall.MS_NODEV
 
-// SystemdCgroups indicates whether systemd cgroup implemenation is in use or not
-var SystemdCgroups = false
-
 // New returns the docker default configuration for libcontainer
 func New() *configs.Config {
 	container := &configs.Config{
@@ -40,7 +37,7 @@ func New() *configs.Config {
 			{Type: "NEWUSER"},
 		}),
 		Cgroups: &configs.Cgroup{
-			Parent: "/docker",
+			ScopePrefix: "docker", // systemd only
 			Resources: &configs.Resources{
 				AllowAllDevices:  false,
 				MemorySwappiness: -1,
@@ -99,10 +96,5 @@ func New() *configs.Config {
 		container.AppArmorProfile = "docker-default"
 	}
 
-	if SystemdCgroups {
-		container.Cgroups.Parent = "system.slice"
-		container.Cgroups.ScopePrefix = "docker"
-	}
-
 	return container
 }