Added a new method cgroups.GetStats() which will return a cgroups.Stats object which will contain all the available cgroup Stats.

Remove old Stats interface in libcontainers cgroups package.
Changed Stats to use unit64 instead of int64 to prevent integer overflow issues.
Updated unit tests.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)

libcontainer/cgroups/fs/blkio.go

@@ -3,7 +3,6 @@ package fs
 import (
 	"bufio"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -57,65 +56,87 @@ examples:
     8:0 Total 0
     Total 0
 */
-func (s *blkioGroup) Stats(d *data) (map[string]int64, error) {
-	var (
-		paramData = make(map[string]int64)
-		params    = []string{
-			"io_service_bytes_recursive",
-			"io_serviced_recursive",
-			"io_queued_recursive",
-		}
-	)
 
-	path, err := d.path("blkio")
-	if err != nil {
-		return nil, err
-	}
-
-	k, v, err := s.getSectors(path)
-	if err != nil {
-		return nil, err
-	}
-	paramData[fmt.Sprintf("blkio.sectors_recursive:%s", k)] = v
-
-	for _, param := range params {
-		f, err := os.Open(filepath.Join(path, fmt.Sprintf("blkio.%s", param)))
-		if err != nil {
-			return nil, err
-		}
-		defer f.Close()
-
-		sc := bufio.NewScanner(f)
-		for sc.Scan() {
-			// format: dev type amount
-			fields := strings.Fields(sc.Text())
-			switch len(fields) {
-			case 3:
-				v, err := strconv.ParseInt(fields[2], 10, 64)
-				if err != nil {
-					return nil, err
-				}
-				paramData[fmt.Sprintf("%s:%s:%s", param, fields[0], fields[1])] = v
-			case 2:
-				// this is the total line, skip
-			default:
-				return nil, ErrNotValidFormat
-			}
-		}
-	}
-	return paramData, nil
+func splitBlkioStatLine(r rune) bool {
+	return r == ' ' || r == ':'
 }
 
-func (s *blkioGroup) getSectors(path string) (string, int64, error) {
-	f, err := os.Open(filepath.Join(path, "blkio.sectors_recursive"))
+func getBlkioStat(path string) ([]cgroups.BlkioStatEntry, error) {
+	var blkioStats []cgroups.BlkioStatEntry
+	f, err := os.Open(path)
 	if err != nil {
-		return "", 0, err
+		return nil, err
 	}
 	defer f.Close()
 
-	data, err := ioutil.ReadAll(f)
-	if err != nil {
-		return "", 0, err
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		// format: dev type amount
+		fields := strings.FieldsFunc(sc.Text(), splitBlkioStatLine)
+		if len(fields) < 3 {
+			if len(fields) == 2 && fields[0] == "Total" {
+				// skip total line
+				continue
+			} else {
+				return nil, fmt.Errorf("Invalid line found while parsing %s: %s", path, sc.Text())
+			}
+		}
+
+		v, err := strconv.ParseUint(fields[0], 10, 64)
+		if err != nil {
+			return nil, err
+		}
+		major := v
+
+		v, err = strconv.ParseUint(fields[1], 10, 64)
+		if err != nil {
+			return nil, err
+		}
+		minor := v
+
+		op := ""
+		valueField := 2
+		if len(fields) == 4 {
+			op = fields[2]
+			valueField = 3
+		}
+		v, err = strconv.ParseUint(fields[valueField], 10, 64)
+		if err != nil {
+			return nil, err
+		}
+		blkioStats = append(blkioStats, cgroups.BlkioStatEntry{Major: major, Minor: minor, Op: op, Value: v})
 	}
-	return getCgroupParamKeyValue(string(data))
+
+	return blkioStats, nil
+}
+
+func (s *blkioGroup) GetStats(d *data, stats *cgroups.Stats) error {
+	var blkioStats []cgroups.BlkioStatEntry
+	var err error
+	path, err := d.path("blkio")
+	if err != nil {
+		return err
+	}
+
+	if blkioStats, err = getBlkioStat(filepath.Join(path, "blkio.sectors_recursive")); err != nil {
+		return err
+	}
+	stats.BlkioStats.SectorsRecursive = blkioStats
+
+	if blkioStats, err = getBlkioStat(filepath.Join(path, "blkio.io_service_bytes_recursive")); err != nil {
+		return err
+	}
+	stats.BlkioStats.IoServiceBytesRecursive = blkioStats
+
+	if blkioStats, err = getBlkioStat(filepath.Join(path, "blkio.io_serviced_recursive")); err != nil {
+		return err
+	}
+	stats.BlkioStats.IoServicedRecursive = blkioStats
+
+	if blkioStats, err = getBlkioStat(filepath.Join(path, "blkio.io_queued_recursive")); err != nil {
+		return err
+	}
+	stats.BlkioStats.IoQueuedRecursive = blkioStats
+
+	return nil
 }