libct/cg: rm dead code to improve clarity

libcontainer/cgroups/fs/fs.go

@@ -196,26 +196,12 @@ func (m *manager) Apply(pid int) (err error) {
 		return cgroups.ErrV1NoUnified
 	}
 
-	m.paths = make(map[string]string)
-	if c.Paths != nil {
-		cgMap, err := cgroups.ParseCgroupFile("/proc/self/cgroup")
-		if err != nil {
-			return err
-		}
-		for name, path := range c.Paths {
-			// XXX(kolyshkin@): why this check is needed?
-			if _, ok := cgMap[name]; ok {
-				m.paths[name] = path
-			}
-		}
-		return cgroups.EnterPid(m.paths, pid)
-	}
-
 	d, err := getCgroupData(m.cgroups, pid)
 	if err != nil {
 		return err
 	}
 
+	m.paths = make(map[string]string)
 	for _, sys := range subsystems {
 		p, err := d.path(sys.Name())
 		if err != nil {
@@ -245,9 +231,6 @@ func (m *manager) Apply(pid int) (err error) {
 }
 
 func (m *manager) Destroy() error {
-	if m.cgroups == nil || m.cgroups.Paths != nil {
-		return nil
-	}
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	return cgroups.RemovePaths(m.paths)
@@ -280,11 +263,6 @@ func (m *manager) Set(r *configs.Resources) error {
 		return nil
 	}
 
-	// If Paths are set, then we are just joining cgroups paths
-	// and there is no need to set any values.
-	if m.cgroups != nil && m.cgroups.Paths != nil {
-		return nil
-	}
 	if r.Unified != nil {
 		return cgroups.ErrV1NoUnified
 	}

libcontainer/cgroups/fs2/defaultpath.go

@@ -35,10 +35,6 @@ func defaultDirPath(c *configs.Cgroup) (string, error) {
 	if (c.Name != "" || c.Parent != "") && c.Path != "" {
 		return "", fmt.Errorf("cgroup: either Path or Name and Parent should be used, got %+v", c)
 	}
-	if len(c.Paths) != 0 {
-		// never set by specconv
-		return "", fmt.Errorf("cgroup: Paths is unsupported, use Path, got %+v", c)
-	}
 
 	// XXX: Do not remove this code. Path safety is important! -- cyphar
 	cgPath := libcontainerUtils.CleanPath(c.Path)

libcontainer/cgroups/systemd/v1.go

@@ -113,21 +113,6 @@ func (m *legacyManager) Apply(pid int) error {
 
 	m.mu.Lock()
 	defer m.mu.Unlock()
-	if c.Paths != nil {
-		paths := make(map[string]string)
-		cgMap, err := cgroups.ParseCgroupFile("/proc/self/cgroup")
-		if err != nil {
-			return err
-		}
-		// XXX(kolyshkin@): why this check is needed?
-		for name, path := range c.Paths {
-			if _, ok := cgMap[name]; ok {
-				paths[name] = path
-			}
-		}
-		m.paths = paths
-		return cgroups.EnterPid(m.paths, pid)
-	}
 
 	if c.Parent != "" {
 		slice = c.Parent
@@ -201,9 +186,6 @@ func (m *legacyManager) Apply(pid int) error {
 }
 
 func (m *legacyManager) Destroy() error {
-	if m.cgroups.Paths != nil {
-		return nil
-	}
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
@@ -388,11 +370,6 @@ func (m *legacyManager) freezeBeforeSet(unitName string, r *configs.Resources) (
 }
 
 func (m *legacyManager) Set(r *configs.Resources) error {
-	// If Paths are set, then we are just joining cgroups paths
-	// and there is no need to set any values.
-	if m.cgroups.Paths != nil {
-		return nil
-	}
 	if r.Unified != nil {
 		return cgroups.ErrV1NoUnified
 	}

libcontainer/cgroups/systemd/v2.go

@@ -234,10 +234,6 @@ func (m *unifiedManager) Apply(pid int) error {
 		properties []systemdDbus.Property
 	)
 
-	if c.Paths != nil {
-		return cgroups.WriteCgroupProc(m.path, pid)
-	}
-
 	slice := "system.slice"
 	if m.rootless {
 		slice = "user.slice"
@@ -296,9 +292,6 @@ func (m *unifiedManager) Apply(pid int) error {
 }
 
 func (m *unifiedManager) Destroy() error {
-	if m.cgroups.Paths != nil {
-		return nil
-	}
 	m.mu.Lock()
 	defer m.mu.Unlock()
 

libcontainer/configs/cgroup_linux.go

@@ -28,10 +28,6 @@ type Cgroup struct {
 	// ScopePrefix describes prefix for the scope name
 	ScopePrefix string `json:"scope_prefix"`
 
-	// Paths represent the absolute cgroups paths to join.
-	// This takes precedence over Path.
-	Paths map[string]string
-
 	// Resources contains various cgroups settings to apply
 	*Resources