small refactor

Signed-off-by: Wang Long <[email protected]>

Author: datawolf

libcontainer/cgroups/utils.go

@@ -23,36 +23,14 @@ const (
 
 // https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
 func FindCgroupMountpoint(subsystem string) (string, error) {
-	// We are not using mount.GetMounts() because it's super-inefficient,
-	// parsing it directly sped up x10 times because of not using Sscanf.
-	// It was one of two major performance drawbacks in container start.
-	if !isSubsystemAvailable(subsystem) {
-		return "", NewNotFoundError(subsystem)
-	}
-	f, err := os.Open("/proc/self/mountinfo")
-	if err != nil {
-		return "", err
-	}
-	defer f.Close()
-
-	scanner := bufio.NewScanner(f)
-	for scanner.Scan() {
-		txt := scanner.Text()
-		fields := strings.Split(txt, " ")
-		for _, opt := range strings.Split(fields[len(fields)-1], ",") {
-			if opt == subsystem {
-				return fields[4], nil
-			}
-		}
-	}
-	if err := scanner.Err(); err != nil {
-		return "", err
-	}
-
-	return "", NewNotFoundError(subsystem)
+	mnt, _, err := FindCgroupMountpointAndRoot(subsystem)
+	return mnt, err
 }
 
 func FindCgroupMountpointAndRoot(subsystem string) (string, string, error) {
+	// We are not using mount.GetMounts() because it's super-inefficient,
+	// parsing it directly sped up x10 times because of not using Sscanf.
+	// It was one of two major performance drawbacks in container start.
 	if !isSubsystemAvailable(subsystem) {
 		return "", "", NewNotFoundError(subsystem)
 	}