pkg, cgroups: add initial support for cgroup v2

This is an initial implementation of cgroup v2 support for
pkg/cgroups.  It currently works with crun, with this patch:
https://github.com/giuseppe/crun/pull/49).

It adds the pieces for:

- set PID limit to 1
- retrieve stats so that "podman stats" work.

the only missing part is the support for reading per
CPU stats (that is cpuacct.usage_percpu on cgroup v1), so for now it
always returns an empty result.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

1 files changed, 91 insertions, 43 deletions

diff --git a/pkg/cgroups/blkio.go b/pkg/cgroups/blkio.go
index 8eb54abec..ca9107d97 100644
--- a/pkg/cgroups/blkio.go
+++ b/pkg/cgroups/blkio.go
@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	spec "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/pkg/errors"
 )
 
 type blkioHandler struct {
@@ -29,7 +30,7 @@ func (c *blkioHandler) Apply(ctr *CgroupControl, res *spec.LinuxResources) error
 // Create the cgroup
 func (c *blkioHandler) Create(ctr *CgroupControl) (bool, error) {
 	if ctr.cgroup2 {
-		return false, fmt.Errorf("function not implemented yet")
+		return false, fmt.Errorf("io create not implemented for cgroup v2")
 	}
 	return ctr.createCgroupDirectory(Blkio)
 }
@@ -44,57 +45,104 @@ func (c *blkioHandler) Stat(ctr *CgroupControl, m *Metrics) error {
 	var ioServiceBytesRecursive []BlkIOEntry
 
 	if ctr.cgroup2 {
-		return fmt.Errorf("function not implemented yet")
-	}
-
-	BlkioRoot := ctr.getCgroupv1Path(Blkio)
-
-	p := filepath.Join(BlkioRoot, "blkio.throttle.io_service_bytes_recursive")
-	f, err := os.Open(p)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-		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], ":")
-		if len(d) != 2 {
-			continue
-		}
-		minor, err := strconv.ParseUint(d[0], 10, 0)
+		// 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 := BlkIOEntry{
+					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 os.IsNotExist(err) {
+				return nil
+			}
+			return errors.Wrapf(err, "open %s", p)
 		}
+		defer f.Close()
 
-		op := parts[1]
+		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
+			}
+			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
+			}
 
-		value, err := strconv.ParseUint(parts[2], 10, 0)
-		if err != nil {
-			return err
+			op := parts[1]
+
+			value, err := strconv.ParseUint(parts[2], 10, 0)
+			if err != nil {
+				return err
+			}
+			entry := BlkIOEntry{
+				Op:    op,
+				Major: major,
+				Minor: minor,
+				Value: value,
+			}
+			ioServiceBytesRecursive = append(ioServiceBytesRecursive, entry)
 		}
-		entry := BlkIOEntry{
-			Op:    op,
-			Major: major,
-			Minor: minor,
-			Value: value,
+		if err := scanner.Err(); err != nil {
+			return errors.Wrapf(err, "parse %s", p)
 		}
-		ioServiceBytesRecursive = append(ioServiceBytesRecursive, entry)
-	}
-	if err := scanner.Err(); err != nil {
-		return err
 	}
 	m.Blkio = BlkioMetrics{IoServiceBytesRecursive: ioServiceBytesRecursive}
 	return nil