common: remove Cgroups v1 support

Removes all conditionals for IsCgroup2UnifiedMode and cgroupv2.Enabled
and assumes Cgroups v2. Also removes `cgroup2` and `additionalControllers` from
CgroupControl struct and all the conditionals resulting from it.

pkg/cgroups.IsCgroup2UnifiedMode is being retained as it will be used in
the dependent tools as a single check for v1/v2.

Fixes: RUN-3567 (partly)

Signed-off-by: Lokesh Mandvekar <[email protected]>

Author: lsm5

common/pkg/cgroups/blkio_linux.go

@@ -3,10 +3,6 @@
 package cgroups
 
 import (
-	"bufio"
-	"errors"
-	"fmt"
-	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -26,23 +22,16 @@ func getBlkioHandler() *linuxBlkioHandler {
 
 // Apply set the specified constraints.
 func (c *linuxBlkioHandler) Apply(ctr *CgroupControl, res *cgroups.Resources) error {
-	if ctr.cgroup2 {
-		man, err := fs2.NewManager(ctr.config, filepath.Join(cgroupRoot, ctr.config.Path))
-		if err != nil {
-			return err
-		}
-		return man.Set(res)
+	man, err := fs2.NewManager(ctr.config, filepath.Join(cgroupRoot, ctr.config.Path))
+	if err != nil {
+		return err
 	}
-	path := filepath.Join(cgroupRoot, Blkio, ctr.config.Path)
-	return c.Blkio.Set(path, res)
+	return man.Set(res)
 }
 
 // Create the cgroup.
 func (c *linuxBlkioHandler) Create(ctr *CgroupControl) (bool, error) {
-	if ctr.cgroup2 {
-		return false, nil
-	}
-	return ctr.createCgroupDirectory(Blkio)
+	return false, nil
 }
 
 // Destroy the cgroup.
@@ -54,94 +43,45 @@ func (c *linuxBlkioHandler) Destroy(ctr *CgroupControl) error {
 func (c *linuxBlkioHandler) Stat(ctr *CgroupControl, m *cgroups.Stats) error {
 	var ioServiceBytesRecursive []cgroups.BlkioStatEntry
 
-	if ctr.cgroup2 {
-		// more details on the io.stat file format:X https://facebookmicrosites.github.io/cgroup2/docs/io-controller.html
-		values, err := readCgroup2MapFile(ctr, "io.stat")
+	// more details on the io.stat file format:X https://facebookmicrosites.github.io/cgroup2/docs/io-controller.html
+	values, err := readCgroup2MapFile(ctr, "io.stat")
+	if err != nil {
+		return err
+	}
+	for k, v := range values {
+		d := strings.Split(k, ":")
+		if len(d) != 2 {
+			continue
+		}
+		minor, err := strconv.ParseUint(d[0], 10, 0)
 		if err != nil {
 			return err
 		}
-		for k, v := range values {
-			d := strings.Split(k, ":")
-			if len(d) != 2 {
-				continue
-			}
-			minor, err := strconv.ParseUint(d[0], 10, 0)
-			if err != nil {
-				return err
-			}
-			major, err := strconv.ParseUint(d[1], 10, 0)
-			if err != nil {
-				return err
-			}
-
-			for _, item := range v {
-				d := strings.Split(item, "=")
-				if len(d) != 2 {
-					continue
-				}
-				op := d[0]
-
-				// Accommodate the cgroup v1 naming
-				switch op {
-				case "rbytes":
-					op = "read"
-				case "wbytes":
-					op = "write"
-				}
-
-				value, err := strconv.ParseUint(d[1], 10, 0)
-				if err != nil {
-					return err
-				}
-
-				entry := cgroups.BlkioStatEntry{
-					Op:    op,
-					Major: major,
-					Minor: minor,
-					Value: value,
-				}
-				ioServiceBytesRecursive = append(ioServiceBytesRecursive, entry)
-			}
-		}
-	} else {
-		BlkioRoot := ctr.getCgroupv1Path(Blkio)
-
-		p := filepath.Join(BlkioRoot, "blkio.throttle.io_service_bytes_recursive")
-		f, err := os.Open(p)
+		major, err := strconv.ParseUint(d[1], 10, 0)
 		if err != nil {
-			if errors.Is(err, os.ErrNotExist) {
-				return nil
-			}
-			return fmt.Errorf("open %s: %w", p, err)
+			return err
 		}
-		defer f.Close()
 
-		scanner := bufio.NewScanner(f)
-		for scanner.Scan() {
-			line := scanner.Text()
-			parts := strings.Fields(line)
-			if len(parts) < 3 {
-				continue
-			}
-			d := strings.Split(parts[0], ":")
+		for _, item := range v {
+			d := strings.Split(item, "=")
 			if len(d) != 2 {
 				continue
 			}
-			minor, err := strconv.ParseUint(d[0], 10, 0)
-			if err != nil {
-				return err
-			}
-			major, err := strconv.ParseUint(d[1], 10, 0)
-			if err != nil {
-				return err
+			op := d[0]
+
+			// Accommodate the cgroup v1 naming
+			switch op {
+			case "rbytes":
+				op = "read"
+			case "wbytes":
+				op = "write"
 			}
 
-			op := parts[1]
-
-			value, err := strconv.ParseUint(parts[2], 10, 0)
+			value, err := strconv.ParseUint(d[1], 10, 0)
 			if err != nil {
 				return err
 			}
+
 			entry := cgroups.BlkioStatEntry{
 				Op:    op,
 				Major: major,
@@ -150,9 +90,6 @@ func (c *linuxBlkioHandler) Stat(ctr *CgroupControl, m *cgroups.Stats) error {
 			}
 			ioServiceBytesRecursive = append(ioServiceBytesRecursive, entry)
 		}
-		if err := scanner.Err(); err != nil {
-			return fmt.Errorf("parse %s: %w", p, err)
-		}
 	}
 	m.BlkioStats.IoServiceBytesRecursive = ioServiceBytesRecursive
 	return nil