libcontainerd/supervisor: use pkg/pidfile for reading and writing pidfile

Also updated a variable name that collided with a package const.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libcontainerd/supervisor/remote_daemon.go

@@ -2,18 +2,17 @@ package supervisor // import "github.com/docker/docker/libcontainerd/supervisor"
 
 import (
 	"context"
-	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
-	"strconv"
 	"strings"
 	"time"
 
 	"github.com/containerd/containerd"
 	"github.com/containerd/containerd/services/server/config"
 	"github.com/containerd/containerd/sys"
+	"github.com/docker/docker/pkg/pidfile"
 	"github.com/docker/docker/pkg/process"
 	"github.com/docker/docker/pkg/system"
 	"github.com/pelletier/go-toml"
@@ -125,34 +124,6 @@ func (r *remote) WaitTimeout(d time.Duration) error {
 func (r *remote) Address() string {
 	return r.GRPC.Address
 }
-func (r *remote) getContainerdPid() (int, error) {
-	f, err := os.OpenFile(r.pidFile, os.O_RDWR, 0600)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return -1, nil
-		}
-		return -1, err
-	}
-	defer f.Close()
-
-	b := make([]byte, 8)
-	n, err := f.Read(b)
-	if err != nil && err != io.EOF {
-		return -1, err
-	}
-
-	if n > 0 {
-		pid, err := strconv.ParseUint(string(b[:n]), 10, 64)
-		if err != nil {
-			return -1, err
-		}
-		if process.Alive(int(pid)) {
-			return int(pid), nil
-		}
-	}
-
-	return -1, nil
-}
 
 func (r *remote) getContainerdConfig() (string, error) {
 	f, err := os.OpenFile(r.configFile, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0600)
@@ -168,23 +139,22 @@ func (r *remote) getContainerdConfig() (string, error) {
 }
 
 func (r *remote) startContainerd() error {
-	pid, err := r.getContainerdPid()
-	if err != nil {
+	pid, err := pidfile.Read(r.pidFile)
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
 		return err
 	}
 
-	if pid != -1 {
+	if pid > 0 {
 		r.daemonPid = pid
 		r.logger.WithField("pid", pid).Infof("%s is still running", binaryName)
 		return nil
 	}
 
-	configFile, err := r.getContainerdConfig()
+	cfgFile, err := r.getContainerdConfig()
 	if err != nil {
 		return err
 	}
-
-	args := []string{"--config", configFile}
+	args := []string{"--config", cfgFile}
 
 	if r.logLevel != "" {
 		args = append(args, "--log-level", r.logLevel)
@@ -237,7 +207,7 @@ func (r *remote) startContainerd() error {
 		r.logger.WithError(err).Warn("failed to adjust OOM score")
 	}
 
-	err = os.WriteFile(r.pidFile, []byte(strconv.Itoa(r.daemonPid)), 0660)
+	err = pidfile.Write(r.pidFile, r.daemonPid)
 	if err != nil {
 		process.Kill(r.daemonPid)
 		return errors.Wrap(err, "libcontainerd: failed to save daemon pid to disk")