Assorted minor nits in libcontainer

libcontainer/cgroups/systemd/unified_hierarchy.go

@@ -3,6 +3,7 @@
 package systemd
 
 import (
+	"bytes"
 	"fmt"
 	"io/ioutil"
 	"math"
@@ -211,15 +212,8 @@ func createCgroupsv2Path(path string) (Err error) {
 		return fmt.Errorf("invalid cgroup path %s", path)
 	}
 
-	res := ""
-	for i, c := range strings.Split(strings.TrimSpace(string(content)), " ") {
-		if i == 0 {
-			res = fmt.Sprintf("+%s", c)
-		} else {
-			res = res + fmt.Sprintf(" +%s", c)
-		}
-	}
-	resByte := []byte(res)
+	ctrs := bytes.Fields(content)
+	res := append([]byte("+"), bytes.Join(ctrs, []byte(" +"))...)
 
 	current := "/sys/fs"
 	elements := strings.Split(path, "/")
@@ -240,7 +234,7 @@ func createCgroupsv2Path(path string) (Err error) {
 			}
 		}
 		if i < len(elements[3:])-1 {
-			if err := ioutil.WriteFile(filepath.Join(current, "cgroup.subtree_control"), resByte, 0755); err != nil {
+			if err := ioutil.WriteFile(filepath.Join(current, "cgroup.subtree_control"), res, 0755); err != nil {
 				return err
 			}
 		}

libcontainer/cgroups/utils.go

@@ -358,8 +358,8 @@ func getCgroupPathHelper(subsystem, cgroup string) (string, error) {
 	return filepath.Join(mnt, relCgroup), nil
 }
 
-func readProcsFile(dir string) ([]int, error) {
-	f, err := os.Open(filepath.Join(dir, CgroupProcesses))
+func readProcsFile(file string) ([]int, error) {
+	f, err := os.Open(file)
 	if err != nil {
 		return nil, err
 	}
@@ -514,8 +514,8 @@ func getHugePageSizeFromFilenames(fileNames []string) ([]string, error) {
 }
 
 // GetPids returns all pids, that were added to cgroup at path.
-func GetPids(path string) ([]int, error) {
-	return readProcsFile(path)
+func GetPids(dir string) ([]int, error) {
+	return readProcsFile(filepath.Join(dir, CgroupProcesses))
 }
 
 // GetAllPids returns all pids, that were added to cgroup at path and to all its
@@ -524,14 +524,13 @@ func GetAllPids(path string) ([]int, error) {
 	var pids []int
 	// collect pids from all sub-cgroups
 	err := filepath.Walk(path, func(p string, info os.FileInfo, iErr error) error {
-		dir, file := filepath.Split(p)
-		if file != CgroupProcesses {
-			return nil
-		}
 		if iErr != nil {
 			return iErr
 		}
-		cPids, err := readProcsFile(dir)
+		if info.IsDir() || info.Name() != CgroupProcesses {
+			return nil
+		}
+		cPids, err := readProcsFile(p)
 		if err != nil {
 			return err
 		}

libcontainer/intelrdt/intelrdt.go

@@ -758,7 +758,7 @@ type LastCmdError struct {
 }
 
 func (e *LastCmdError) Error() string {
-	return fmt.Sprintf(e.Err.Error() + ", last_cmd_status: " + e.LastCmdStatus)
+	return e.Err.Error() + ", last_cmd_status: " + e.LastCmdStatus
 }
 
 func NewLastCmdError(err error) error {