libcontainer/cgroups/fs/blkio: support BFQ weight[_device]

- Update the blkio cgroup to support the BFQ I/O Scheduler, that has
  replaced CFQ in the Linux kernel.
- BFQ is controlled through blkio.bfq.weight[_device] instead of
  CFQ's blkio.weight[_device] in cgroups v1.
- BFQ does not support blkio.leaf_weight[_device], so that behavior
  remains untouched.
- Do not change behavior on legacy CFQ systems.
- Enable using blkio weights on BFQ systems.

Signed-off-by: Antti Kervinen <antti.kervinen@intel.com>

libcontainer/cgroups/fs/blkio.go

@@ -6,6 +6,7 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strconv"
 	"strings"
 
@@ -14,7 +15,10 @@ import (
 	"github.com/opencontainers/runc/libcontainer/configs"
 )
 
-type BlkioGroup struct{}
+type BlkioGroup struct {
+	weightFilename       string
+	weightDeviceFilename string
+}
 
 func (s *BlkioGroup) Name() string {
 	return "blkio"
@@ -25,8 +29,9 @@ func (s *BlkioGroup) Apply(path string, d *cgroupData) error {
 }
 
 func (s *BlkioGroup) Set(path string, r *configs.Resources) error {
+	s.detectWeightFilenames(path)
 	if r.BlkioWeight != 0 {
-		if err := fscommon.WriteFile(path, "blkio.weight", strconv.FormatUint(uint64(r.BlkioWeight), 10)); err != nil {
+		if err := fscommon.WriteFile(path, s.weightFilename, strconv.FormatUint(uint64(r.BlkioWeight), 10)); err != nil {
 			return err
 		}
 	}
@@ -37,7 +42,7 @@ func (s *BlkioGroup) Set(path string, r *configs.Resources) error {
 		}
 	}
 	for _, wd := range r.BlkioWeightDevice {
-		if err := fscommon.WriteFile(path, "blkio.weight_device", wd.WeightString()); err != nil {
+		if err := fscommon.WriteFile(path, s.weightDeviceFilename, wd.WeightString()); err != nil {
 			return err
 		}
 		if err := fscommon.WriteFile(path, "blkio.leaf_weight_device", wd.LeafWeightString()); err != nil {
@@ -287,3 +292,17 @@ func (s *BlkioGroup) GetStats(path string, stats *cgroups.Stats) error {
 	}
 	return nil
 }
+
+func (s *BlkioGroup) detectWeightFilenames(path string) {
+	if s.weightFilename != "" {
+		// Already detected.
+		return
+	}
+	if cgroups.PathExists(filepath.Join(path, "blkio.weight")) {
+		s.weightFilename = "blkio.weight"
+		s.weightDeviceFilename = "blkio.weight_device"
+	} else {
+		s.weightFilename = "blkio.bfq.weight"
+		s.weightDeviceFilename = "blkio.bfq.weight_device"
+	}
+}

libcontainer/cgroups/fs/blkio_test.go

@@ -179,23 +179,24 @@ func TestBlkioSetWeight(t *testing.T) {
 		weightAfter  = 200
 	)
 
+	blkio := &BlkioGroup{}
+	blkio.detectWeightFilenames(helper.CgroupPath)
 	helper.writeFileContents(map[string]string{
-		"blkio.weight": strconv.Itoa(weightBefore),
+		blkio.weightFilename: strconv.Itoa(weightBefore),
 	})
 
 	helper.CgroupData.config.Resources.BlkioWeight = weightAfter
-	blkio := &BlkioGroup{}
 	if err := blkio.Set(helper.CgroupPath, helper.CgroupData.config.Resources); err != nil {
 		t.Fatal(err)
 	}
 
-	value, err := fscommon.GetCgroupParamUint(helper.CgroupPath, "blkio.weight")
+	value, err := fscommon.GetCgroupParamUint(helper.CgroupPath, blkio.weightFilename)
 	if err != nil {
-		t.Fatalf("Failed to parse blkio.weight - %s", err)
+		t.Fatal(err)
 	}
 
 	if value != weightAfter {
-		t.Fatal("Got the wrong value, set blkio.weight failed.")
+		t.Fatalf("Got the wrong value, set %s failed.", blkio.weightFilename)
 	}
 }
 
@@ -210,23 +211,24 @@ func TestBlkioSetWeightDevice(t *testing.T) {
 	wd := configs.NewWeightDevice(8, 0, 500, 0)
 	weightDeviceAfter := wd.WeightString()
 
+	blkio := &BlkioGroup{}
+	blkio.detectWeightFilenames(helper.CgroupPath)
 	helper.writeFileContents(map[string]string{
-		"blkio.weight_device": weightDeviceBefore,
+		blkio.weightDeviceFilename: weightDeviceBefore,
 	})
 
 	helper.CgroupData.config.Resources.BlkioWeightDevice = []*configs.WeightDevice{wd}
-	blkio := &BlkioGroup{}
 	if err := blkio.Set(helper.CgroupPath, helper.CgroupData.config.Resources); err != nil {
 		t.Fatal(err)
 	}
 
-	value, err := fscommon.GetCgroupParamString(helper.CgroupPath, "blkio.weight_device")
+	value, err := fscommon.GetCgroupParamString(helper.CgroupPath, blkio.weightDeviceFilename)
 	if err != nil {
-		t.Fatalf("Failed to parse blkio.weight_device - %s", err)
+		t.Fatal(err)
 	}
 
 	if value != weightDeviceAfter {
-		t.Fatal("Got the wrong value, set blkio.weight_device failed.")
+		t.Fatalf("Got the wrong value, set %s failed.", blkio.weightDeviceFilename)
 	}
 }
 
@@ -247,23 +249,24 @@ func TestBlkioSetMultipleWeightDevice(t *testing.T) {
 	// is present will suffice for the test to ensure multiple writes are done.
 	weightDeviceAfter := wd2.WeightString()
 
+	blkio := &BlkioGroup{}
+	blkio.detectWeightFilenames(helper.CgroupPath)
 	helper.writeFileContents(map[string]string{
-		"blkio.weight_device": weightDeviceBefore,
+		blkio.weightDeviceFilename: weightDeviceBefore,
 	})
 
 	helper.CgroupData.config.Resources.BlkioWeightDevice = []*configs.WeightDevice{wd1, wd2}
-	blkio := &BlkioGroup{}
 	if err := blkio.Set(helper.CgroupPath, helper.CgroupData.config.Resources); err != nil {
 		t.Fatal(err)
 	}
 
-	value, err := fscommon.GetCgroupParamString(helper.CgroupPath, "blkio.weight_device")
+	value, err := fscommon.GetCgroupParamString(helper.CgroupPath, blkio.weightDeviceFilename)
 	if err != nil {
-		t.Fatalf("Failed to parse blkio.weight_device - %s", err)
+		t.Fatal(err)
 	}
 
 	if value != weightDeviceAfter {
-		t.Fatal("Got the wrong value, set blkio.weight_device failed.")
+		t.Fatalf("Got the wrong value, set %s failed.", blkio.weightDeviceFilename)
 	}
 }