change hard code: add some overlay2 constant to replace the hard code.

Signed-off-by: Xiao YongBiao <xyb4638@gmail.com>

daemon/graphdriver/overlay2/check.go

@@ -43,10 +43,10 @@ func doesSupportNativeDiff(d string) error {
 	if err := os.Mkdir(filepath.Join(td, "l3"), 0755); err != nil {
 		return err
 	}
-	if err := os.Mkdir(filepath.Join(td, "work"), 0755); err != nil {
+	if err := os.Mkdir(filepath.Join(td, workDirName), 0755); err != nil {
 		return err
 	}
-	if err := os.Mkdir(filepath.Join(td, "merged"), 0755); err != nil {
+	if err := os.Mkdir(filepath.Join(td, mergedDirName), 0755); err != nil {
 		return err
 	}
 
@@ -55,18 +55,18 @@ func doesSupportNativeDiff(d string) error {
 		return errors.Wrap(err, "failed to set opaque flag on middle layer")
 	}
 
-	opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", path.Join(td, "l2"), path.Join(td, "l1"), path.Join(td, "l3"), path.Join(td, "work"))
-	if err := unix.Mount("overlay", filepath.Join(td, "merged"), "overlay", 0, opts); err != nil {
+	opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", path.Join(td, "l2"), path.Join(td, "l1"), path.Join(td, "l3"), path.Join(td, workDirName))
+	if err := unix.Mount("overlay", filepath.Join(td, mergedDirName), "overlay", 0, opts); err != nil {
 		return errors.Wrap(err, "failed to mount overlay")
 	}
 	defer func() {
-		if err := unix.Unmount(filepath.Join(td, "merged"), 0); err != nil {
-			logger.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, "merged"), err)
+		if err := unix.Unmount(filepath.Join(td, mergedDirName), 0); err != nil {
+			logger.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, mergedDirName), err)
 		}
 	}()
 
 	// Touch file in d to force copy up of opaque directory "d" from "l2" to "l3"
-	if err := ioutil.WriteFile(filepath.Join(td, "merged", "d", "f"), []byte{}, 0644); err != nil {
+	if err := ioutil.WriteFile(filepath.Join(td, mergedDirName, "d", "f"), []byte{}, 0644); err != nil {
 		return errors.Wrap(err, "failed to write to merged directory")
 	}
 
@@ -80,7 +80,7 @@ func doesSupportNativeDiff(d string) error {
 	}
 
 	// rename "d1" to "d2"
-	if err := os.Rename(filepath.Join(td, "merged", "d1"), filepath.Join(td, "merged", "d2")); err != nil {
+	if err := os.Rename(filepath.Join(td, mergedDirName, "d1"), filepath.Join(td, mergedDirName, "d2")); err != nil {
 		// if rename failed with syscall.EXDEV, the kernel doesn't have CONFIG_OVERLAY_FS_REDIRECT_DIR enabled
 		if err.(*os.LinkError).Err == syscall.EXDEV {
 			return nil
@@ -116,18 +116,18 @@ func supportsMultipleLowerDir(d string) error {
 		}
 	}()
 
-	for _, dir := range []string{"lower1", "lower2", "upper", "work", "merged"} {
+	for _, dir := range []string{"lower1", "lower2", "upper", workDirName, mergedDirName} {
 		if err := os.Mkdir(filepath.Join(td, dir), 0755); err != nil {
 			return err
 		}
 	}
 
-	opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", path.Join(td, "lower2"), path.Join(td, "lower1"), path.Join(td, "upper"), path.Join(td, "work"))
-	if err := unix.Mount("overlay", filepath.Join(td, "merged"), "overlay", 0, opts); err != nil {
+	opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", path.Join(td, "lower2"), path.Join(td, "lower1"), path.Join(td, "upper"), path.Join(td, workDirName))
+	if err := unix.Mount("overlay", filepath.Join(td, mergedDirName), "overlay", 0, opts); err != nil {
 		return errors.Wrap(err, "failed to mount overlay")
 	}
-	if err := unix.Unmount(filepath.Join(td, "merged"), 0); err != nil {
-		logger.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, "merged"), err)
+	if err := unix.Unmount(filepath.Join(td, mergedDirName), 0); err != nil {
+		logger.Warnf("Failed to unmount check directory %v: %v", filepath.Join(td, mergedDirName), err)
 	}
 	return nil
 }

daemon/graphdriver/overlay2/overlay.go

@@ -71,10 +71,13 @@ var (
 // that mounts do not fail due to length.
 
 const (
-	driverName = "overlay2"
-	linkDir    = "l"
-	lowerFile  = "lower"
-	maxDepth   = 128
+	driverName    = "overlay2"
+	linkDir       = "l"
+	diffDirName   = "diff"
+	workDirName   = "work"
+	mergedDirName = "merged"
+	lowerFile     = "lower"
+	maxDepth      = 128
 
 	// idLength represents the number of random characters
 	// which can be used to create the unique link identifier
@@ -326,9 +329,9 @@ func (d *Driver) GetMetadata(id string) (map[string]string, error) {
 	}
 
 	metadata := map[string]string{
-		"WorkDir":   path.Join(dir, "work"),
-		"MergedDir": path.Join(dir, "merged"),
-		"UpperDir":  path.Join(dir, "diff"),
+		"WorkDir":   path.Join(dir, workDirName),
+		"MergedDir": path.Join(dir, mergedDirName),
+		"UpperDir":  path.Join(dir, diffDirName),
 	}
 
 	lowerDirs, err := d.getLowerDirs(id)
@@ -420,12 +423,12 @@ func (d *Driver) create(id, parent string, opts *graphdriver.CreateOpts) (retErr
 		}
 	}
 
-	if err := idtools.MkdirAndChown(path.Join(dir, "diff"), 0755, root); err != nil {
+	if err := idtools.MkdirAndChown(path.Join(dir, diffDirName), 0755, root); err != nil {
 		return err
 	}
 
 	lid := generateID(idLength)
-	if err := os.Symlink(path.Join("..", id, "diff"), path.Join(d.home, linkDir, lid)); err != nil {
+	if err := os.Symlink(path.Join("..", id, diffDirName), path.Join(d.home, linkDir, lid)); err != nil {
 		return err
 	}
 
@@ -439,7 +442,7 @@ func (d *Driver) create(id, parent string, opts *graphdriver.CreateOpts) (retErr
 		return nil
 	}
 
-	if err := idtools.MkdirAndChown(path.Join(dir, "work"), 0700, root); err != nil {
+	if err := idtools.MkdirAndChown(path.Join(dir, workDirName), 0700, root); err != nil {
 		return err
 	}
 
@@ -555,7 +558,7 @@ func (d *Driver) Get(id, mountLabel string) (_ containerfs.ContainerFS, retErr e
 		return nil, err
 	}
 
-	diffDir := path.Join(dir, "diff")
+	diffDir := path.Join(dir, diffDirName)
 	lowers, err := ioutil.ReadFile(path.Join(dir, lowerFile))
 	if err != nil {
 		// If no lower, just return diff directory
@@ -565,7 +568,7 @@ func (d *Driver) Get(id, mountLabel string) (_ containerfs.ContainerFS, retErr e
 		return nil, err
 	}
 
-	mergedDir := path.Join(dir, "merged")
+	mergedDir := path.Join(dir, mergedDirName)
 	if count := d.ctr.Increment(mergedDir); count > 1 {
 		return containerfs.NewLocalContainerFS(mergedDir), nil
 	}
@@ -583,13 +586,13 @@ func (d *Driver) Get(id, mountLabel string) (_ containerfs.ContainerFS, retErr e
 		}
 	}()
 
-	workDir := path.Join(dir, "work")
+	workDir := path.Join(dir, workDirName)
 	splitLowers := strings.Split(string(lowers), ":")
 	absLowers := make([]string, len(splitLowers))
 	for i, s := range splitLowers {
 		absLowers[i] = path.Join(d.home, s)
 	}
-	opts := indexOff + "lowerdir=" + strings.Join(absLowers, ":") + ",upperdir=" + path.Join(dir, "diff") + ",workdir=" + path.Join(dir, "work")
+	opts := indexOff + "lowerdir=" + strings.Join(absLowers, ":") + ",upperdir=" + diffDir + ",workdir=" + workDir
 	mountData := label.FormatMountLabel(opts, mountLabel)
 	mount := unix.Mount
 	mountTarget := mergedDir
@@ -609,7 +612,7 @@ func (d *Driver) Get(id, mountLabel string) (_ containerfs.ContainerFS, retErr e
 	// fit within a page and relative links make the mount data much
 	// smaller at the expense of requiring a fork exec to chroot.
 	if len(mountData) > pageSize {
-		opts = indexOff + "lowerdir=" + string(lowers) + ",upperdir=" + path.Join(id, "diff") + ",workdir=" + path.Join(id, "work")
+		opts = indexOff + "lowerdir=" + string(lowers) + ",upperdir=" + path.Join(id, diffDirName) + ",workdir=" + path.Join(id, workDirName)
 		mountData = label.FormatMountLabel(opts, mountLabel)
 		if len(mountData) > pageSize {
 			return nil, fmt.Errorf("cannot mount layer, mount label too large %d", len(mountData))
@@ -618,7 +621,7 @@ func (d *Driver) Get(id, mountLabel string) (_ containerfs.ContainerFS, retErr e
 		mount = func(source string, target string, mType string, flags uintptr, label string) error {
 			return mountFrom(d.home, source, target, mType, flags, label)
 		}
-		mountTarget = path.Join(id, "merged")
+		mountTarget = path.Join(id, mergedDirName)
 	}
 
 	if err := mount("overlay", mountTarget, "overlay", 0, mountData); err != nil {
@@ -627,7 +630,7 @@ func (d *Driver) Get(id, mountLabel string) (_ containerfs.ContainerFS, retErr e
 
 	// chown "workdir/work" to the remapped root UID/GID. Overlay fs inside a
 	// user namespace requires this to move a directory from lower to upper.
-	if err := os.Chown(path.Join(workDir, "work"), rootUID, rootGID); err != nil {
+	if err := os.Chown(path.Join(workDir, workDirName), rootUID, rootGID); err != nil {
 		return nil, err
 	}
 
@@ -650,7 +653,7 @@ func (d *Driver) Put(id string) error {
 		return err
 	}
 
-	mountpoint := path.Join(dir, "merged")
+	mountpoint := path.Join(dir, mergedDirName)
 	if count := d.ctr.Decrement(mountpoint); count > 0 {
 		return nil
 	}
@@ -723,7 +726,7 @@ func (d *Driver) ApplyDiff(id string, parent string, diff io.Reader) (size int64
 func (d *Driver) getDiffPath(id string) string {
 	dir := d.dir(id)
 
-	return path.Join(dir, "diff")
+	return path.Join(dir, diffDirName)
 }
 
 // DiffSize calculates the changes between the specified id