Move back to using a scanner in FindCgroupMountpointAndRoot

libcontainer/cgroups/utils.go

@@ -35,17 +35,20 @@ func FindCgroupMountpointAndRoot(cgroupPath, subsystem string) (string, string,
 		return "", "", NewNotFoundError(subsystem)
 	}
 
-	mountinfo, err := ioutil.ReadFile("/proc/self/mountinfo")
+	f, err := os.Open("/proc/self/mountinfo")
 	if err != nil {
 		return "", "", err
 	}
+	defer f.Close()
 
-	return findCgroupMountpointAndRoot(cgroupPath, subsystem, string(mountinfo))
+	return findCgroupMountpointAndRootFromReader(f, cgroupPath, subsystem)
 }
 
-func findCgroupMountpointAndRoot(cgroupPath, subsystem, mountinfo string) (string, string, error) {
-	for _, mountInfoEntry := range strings.Split(mountinfo, "\n") {
-		fields := strings.Fields(mountInfoEntry)
+func findCgroupMountpointAndRootFromReader(reader io.Reader, cgroupPath, subsystem string) (string, string, error) {
+	scanner := bufio.NewScanner(reader)
+	for scanner.Scan() {
+		txt := scanner.Text()
+		fields := strings.Fields(txt)
 		if len(fields) < 5 {
 			continue
 		}
@@ -57,6 +60,9 @@ func findCgroupMountpointAndRoot(cgroupPath, subsystem, mountinfo string) (strin
 			}
 		}
 	}
+	if err := scanner.Err(); err != nil {
+		return "", "", err
+	}
 
 	return "", "", NewNotFoundError(subsystem)
 }

libcontainer/cgroups/utils_test.go

@@ -344,7 +344,7 @@ func TestFindCgroupMountpointAndRoot(t *testing.T) {
 	}
 
 	for _, c := range testCases {
-		mountpoint, _, _ := findCgroupMountpointAndRoot(c.cgroupPath, "devices", fakeMountInfo)
+		mountpoint, _, _ := findCgroupMountpointAndRootFromReader(strings.NewReader(fakeMountInfo), c.cgroupPath, "devices")
 		if mountpoint != c.output {
 			t.Errorf("expected %s, got %s", c.output, mountpoint)
 		}