[DO NOT MERGE] cgroup v1: optimize code to avoid parsing mountinfo if possible

libcontainer/cgroups/fs/blkio.go

@@ -22,12 +22,8 @@ func (s *BlkioGroup) Name() string {
 	return "blkio"
 }
 
-func (s *BlkioGroup) Apply(d *cgroupData) error {
-	_, err := d.join("blkio")
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
+func (s *BlkioGroup) Apply(path string, d *cgroupData) error {
+	return join(path, d.pid)
 }
 
 func (s *BlkioGroup) Set(path string, cgroup *configs.Cgroup) error {
@@ -74,10 +70,6 @@ func (s *BlkioGroup) Set(path string, cgroup *configs.Cgroup) error {
 	return nil
 }
 
-func (s *BlkioGroup) Remove(d *cgroupData) error {
-	return removePath(d.path("blkio"))
-}
-
 /*
 examples:
 

libcontainer/cgroups/fs/cpu.go

@@ -21,17 +21,7 @@ func (s *CpuGroup) Name() string {
 	return "cpu"
 }
 
-func (s *CpuGroup) Apply(d *cgroupData) error {
-	// We always want to join the cpu group, to allow fair cpu scheduling
-	// on a container basis
-	path, err := d.path("cpu")
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return s.ApplyDir(path, d.config, d.pid)
-}
-
-func (s *CpuGroup) ApplyDir(path string, cgroup *configs.Cgroup, pid int) error {
+func (s *CpuGroup) Apply(path string, d *cgroupData) error {
 	// This might happen if we have no cpu cgroup mounted.
 	// Just do nothing and don't fail.
 	if path == "" {
@@ -43,12 +33,12 @@ func (s *CpuGroup) ApplyDir(path string, cgroup *configs.Cgroup, pid int) error
 	// We should set the real-Time group scheduling settings before moving
 	// in the process because if the process is already in SCHED_RR mode
 	// and no RT bandwidth is set, adding it will fail.
-	if err := s.SetRtSched(path, cgroup); err != nil {
+	if err := s.SetRtSched(path, d.config); err != nil {
 		return err
 	}
-	// because we are not using d.join we need to place the pid into the procs file
-	// unlike the other subsystems
-	return cgroups.WriteCgroupProc(path, pid)
+	// Since we are not using join(), we need to place the pid
+	// into the procs file unlike other subsystems.
+	return cgroups.WriteCgroupProc(path, d.pid)
 }
 
 func (s *CpuGroup) SetRtSched(path string, cgroup *configs.Cgroup) error {
@@ -96,10 +86,6 @@ func (s *CpuGroup) Set(path string, cgroup *configs.Cgroup) error {
 	return s.SetRtSched(path, cgroup)
 }
 
-func (s *CpuGroup) Remove(d *cgroupData) error {
-	return removePath(d.path("cpu"))
-}
-
 func (s *CpuGroup) GetStats(path string, stats *cgroups.Stats) error {
 	f, err := os.Open(filepath.Join(path, "cpu.stat"))
 	if err != nil {

libcontainer/cgroups/fs/cpu_test.go

@@ -182,7 +182,9 @@ func TestCpuSetRtSchedAtApply(t *testing.T) {
 	helper.CgroupData.config.Resources.CpuRtRuntime = rtRuntimeAfter
 	helper.CgroupData.config.Resources.CpuRtPeriod = rtPeriodAfter
 	cpu := &CpuGroup{}
-	if err := cpu.ApplyDir(helper.CgroupPath, helper.CgroupData.config, 1234); err != nil {
+
+	helper.CgroupData.pid = 1234
+	if err := cpu.Apply(helper.CgroupPath, helper.CgroupData); err != nil {
 		t.Fatal(err)
 	}
 

libcontainer/cgroups/fs/cpuacct.go

@@ -40,23 +40,14 @@ func (s *CpuacctGroup) Name() string {
 	return "cpuacct"
 }
 
-func (s *CpuacctGroup) Apply(d *cgroupData) error {
-	// we just want to join this group even though we don't set anything
-	if _, err := d.join("cpuacct"); err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-
-	return nil
+func (s *CpuacctGroup) Apply(path string, d *cgroupData) error {
+	return join(path, d.pid)
 }
 
 func (s *CpuacctGroup) Set(path string, cgroup *configs.Cgroup) error {
 	return nil
 }
 
-func (s *CpuacctGroup) Remove(d *cgroupData) error {
-	return removePath(d.path("cpuacct"))
-}
-
 func (s *CpuacctGroup) GetStats(path string, stats *cgroups.Stats) error {
 	userModeUsage, kernelModeUsage, err := getCpuUsageBreakdown(path)
 	if err != nil {

libcontainer/cgroups/fs/cpuset.go

@@ -23,12 +23,8 @@ func (s *CpusetGroup) Name() string {
 	return "cpuset"
 }
 
-func (s *CpusetGroup) Apply(d *cgroupData) error {
-	dir, err := d.path("cpuset")
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return s.ApplyDir(dir, d.config, d.pid)
+func (s *CpusetGroup) Apply(path string, d *cgroupData) error {
+	return s.ApplyDir(path, d.config, d.pid)
 }
 
 func (s *CpusetGroup) Set(path string, cgroup *configs.Cgroup) error {
@@ -45,10 +41,6 @@ func (s *CpusetGroup) Set(path string, cgroup *configs.Cgroup) error {
 	return nil
 }
 
-func (s *CpusetGroup) Remove(d *cgroupData) error {
-	return removePath(d.path("cpuset"))
-}
-
 func (s *CpusetGroup) GetStats(path string, stats *cgroups.Stats) error {
 	return nil
 }

libcontainer/cgroups/fs/devices.go

@@ -22,14 +22,13 @@ func (s *DevicesGroup) Name() string {
 	return "devices"
 }
 
-func (s *DevicesGroup) Apply(d *cgroupData) error {
-	_, err := d.join("devices")
-	if err != nil {
-		// We will return error even it's `not found` error, devices
-		// cgroup is hard requirement for container's security.
-		return err
+func (s *DevicesGroup) Apply(path string, d *cgroupData) error {
+	if path == "" {
+		// Return error here, since devices cgroup
+		// is a hard requirement for container's security.
+		return errSubsystemDoesNotExist
 	}
-	return nil
+	return join(path, d.pid)
 }
 
 func loadEmulator(path string) (*devices.Emulator, error) {
@@ -103,10 +102,6 @@ func (s *DevicesGroup) Set(path string, cgroup *configs.Cgroup) error {
 	return nil
 }
 
-func (s *DevicesGroup) Remove(d *cgroupData) error {
-	return removePath(d.path("devices"))
-}
-
 func (s *DevicesGroup) GetStats(path string, stats *cgroups.Stats) error {
 	return nil
 }

libcontainer/cgroups/fs/freezer.go

@@ -22,12 +22,8 @@ func (s *FreezerGroup) Name() string {
 	return "freezer"
 }
 
-func (s *FreezerGroup) Apply(d *cgroupData) error {
-	_, err := d.join("freezer")
-	if err != nil && !cgroups.IsNotFound(err) {
-		return err
-	}
-	return nil
+func (s *FreezerGroup) Apply(path string, d *cgroupData) error {
+	return join(path, d.pid)
 }
 
 func (s *FreezerGroup) Set(path string, cgroup *configs.Cgroup) error {
@@ -61,10 +57,6 @@ func (s *FreezerGroup) Set(path string, cgroup *configs.Cgroup) error {
 	return nil
 }
 
-func (s *FreezerGroup) Remove(d *cgroupData) error {
-	return removePath(d.path("freezer"))
-}
-
 func (s *FreezerGroup) GetStats(path string, stats *cgroups.Stats) error {
 	return nil
 }