BlockVolumesSupport: CRI, VolumeManager and OperationExecutor changes

This patch contains following changes.
- container runtime changes for adding block devices
- volumemanager changes
- operationexecutor changes

pkg/volume/util/util_linux.go

@@ -0,0 +1,106 @@
+// +build linux
+
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/golang/glog"
+)
+
+// AttachFileDevice takes a path to a regular file and makes it available as an
+// attached block device.
+func (v VolumePathHandler) AttachFileDevice(path string) (string, error) {
+	blockDevicePath, err := v.GetLoopDevice(path)
+	if err != nil && err.Error() != ErrDeviceNotFound {
+		return "", err
+	}
+
+	// If no existing loop device for the path, create one
+	if blockDevicePath == "" {
+		glog.V(4).Infof("Creating device for path: %s", path)
+		blockDevicePath, err = makeLoopDevice(path)
+		if err != nil {
+			return "", err
+		}
+	}
+	return blockDevicePath, nil
+}
+
+// GetLoopDevice returns the full path to the loop device associated with the given path.
+func (v VolumePathHandler) GetLoopDevice(path string) (string, error) {
+	_, err := os.Stat(path)
+	if os.IsNotExist(err) {
+		return "", errors.New(ErrNotAvailable)
+	}
+	if err != nil {
+		return "", fmt.Errorf("not attachable: %v", err)
+	}
+
+	args := []string{"-j", path}
+	cmd := exec.Command(losetupPath, args...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		glog.V(2).Infof("Failed device discover command for path %s: %v", path, err)
+		return "", err
+	}
+	return parseLosetupOutputForDevice(out)
+}
+
+func makeLoopDevice(path string) (string, error) {
+	args := []string{"-f", "--show", path}
+	cmd := exec.Command(losetupPath, args...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		glog.V(2).Infof("Failed device create command for path %s: %v", path, err)
+		return "", err
+	}
+	return parseLosetupOutputForDevice(out)
+}
+
+// RemoveLoopDevice removes specified loopback device
+func (v VolumePathHandler) RemoveLoopDevice(device string) error {
+	args := []string{"-d", device}
+	cmd := exec.Command(losetupPath, args...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		if !strings.Contains(string(out), "No such device or address") {
+			return err
+		}
+	}
+	return nil
+}
+
+func parseLosetupOutputForDevice(output []byte) (string, error) {
+	if len(output) == 0 {
+		return "", errors.New(ErrDeviceNotFound)
+	}
+
+	// losetup returns device in the format:
+	// /dev/loop1: [0073]:148662 (/dev/sda)
+	device := strings.TrimSpace(strings.SplitN(string(output), ":", 2)[0])
+	if len(device) == 0 {
+		return "", errors.New(ErrDeviceNotFound)
+	}
+	return device, nil
+}