Revert Cgroups V1 removal

This broke a lot of stuff, so this should only be re-reverted once
things are known to work in Podman and Buildah.

Commits reverted:

- e94388d
- 26e4421
- b7be55c
- cce5ec8
- 5f98dfb
- ceaec36
- ed47881
- 2cf45c5
- 80309d7
- 8251431
- ff00d90
- 213e7ec

Ref: containers#417

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

Author: lsm5

common/pkg/cgroups/blkio_linux.go

@@ -3,6 +3,10 @@
 package cgroups
 
 import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -22,56 +26,122 @@ func getBlkioHandler() *linuxBlkioHandler {
 
 // Apply set the specified constraints.
 func (c *linuxBlkioHandler) Apply(ctr *CgroupControl, res *cgroups.Resources) error {
-	man, err := fs2.NewManager(ctr.config, filepath.Join(cgroupRoot, ctr.config.Path))
-	if err != nil {
-		return err
+	if ctr.cgroup2 {
+		man, err := fs2.NewManager(ctr.config, filepath.Join(cgroupRoot, ctr.config.Path))
+		if err != nil {
+			return err
+		}
+		return man.Set(res)
+	}
+	path := filepath.Join(cgroupRoot, Blkio, ctr.config.Path)
+	return c.Blkio.Set(path, res)
+}
+
+// Create the cgroup.
+func (c *linuxBlkioHandler) Create(ctr *CgroupControl) (bool, error) {
+	if ctr.cgroup2 {
+		return false, nil
 	}
-	return man.Set(res)
+	return ctr.createCgroupDirectory(Blkio)
+}
+
+// Destroy the cgroup.
+func (c *linuxBlkioHandler) Destroy(ctr *CgroupControl) error {
+	return rmDirRecursively(ctr.getCgroupv1Path(Blkio))
 }
 
 // Stat fills a metrics structure with usage stats for the controller.
 func (c *linuxBlkioHandler) Stat(ctr *CgroupControl, m *cgroups.Stats) error {
 	var ioServiceBytesRecursive []cgroups.BlkioStatEntry
 
-	// 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 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")
 		if err != nil {
 			return err
 		}
-		major, err := strconv.ParseUint(d[1], 10, 0)
+		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)
 		if err != nil {
-			return err
+			if errors.Is(err, os.ErrNotExist) {
+				return nil
+			}
+			return fmt.Errorf("open %s: %w", p, err)
 		}
+		defer f.Close()
 
-		for _, item := range v {
-			d := strings.Split(item, "=")
+		scanner := bufio.NewScanner(f)
+		for scanner.Scan() {
+			line := scanner.Text()
+			parts := strings.Fields(line)
+			if len(parts) < 3 {
+				continue
+			}
+			d := strings.Split(parts[0], ":")
 			if len(d) != 2 {
 				continue
 			}
-			op := d[0]
-
-			// Accommodate the cgroup v1 naming
-			switch op {
-			case "rbytes":
-				op = "read"
-			case "wbytes":
-				op = "write"
+			minor, err := strconv.ParseUint(d[0], 10, 0)
+			if err != nil {
+				return err
 			}
-
-			value, err := strconv.ParseUint(d[1], 10, 0)
+			major, err := strconv.ParseUint(d[1], 10, 0)
 			if err != nil {
 				return err
 			}
 
+			op := parts[1]
+
+			value, err := strconv.ParseUint(parts[2], 10, 0)
+			if err != nil {
+				return err
+			}
 			entry := cgroups.BlkioStatEntry{
 				Op:    op,
 				Major: major,
@@ -80,6 +150,9 @@ 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