Add create layer cmd to create filesystem changeset

Signed-off-by: Lei Jitang <[email protected]>

.gitignore

@@ -1,3 +1,4 @@
 /oci-create-runtime-bundle
 /oci-unpack
 /oci-image-validate
+/oci-create-layer

Makefile

@@ -22,6 +22,7 @@ tools:
 	go build ./cmd/oci-create-runtime-bundle
 	go build ./cmd/oci-unpack
 	go build ./cmd/oci-image-validate
+	go build ./cmd/oci-create-layer
 
 lint:
 	@echo "checking lint"

cmd/oci-create-layer/main.go

@@ -0,0 +1,80 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 main
+
+import (
+	"log"
+	"os"
+
+	"github.com/opencontainers/image-tools/image"
+	"github.com/spf13/cobra"
+)
+
+type layerCmd struct {
+	stdout *log.Logger
+	stderr *log.Logger
+	dest   string
+}
+
+func main() {
+	stdout := log.New(os.Stdout, "", 0)
+	stderr := log.New(os.Stderr, "", 0)
+
+	cmd := newLayerCmd(stdout, stderr)
+	if err := cmd.Execute(); err != nil {
+		stderr.Println(err)
+		os.Exit(1)
+	}
+}
+
+func newLayerCmd(stdout, stderr *log.Logger) *cobra.Command {
+	v := &layerCmd{
+		stdout: stdout,
+		stderr: stderr,
+	}
+
+	cmd := &cobra.Command{
+		Use:   "oci-create-layer [child] [parent]",
+		Short: "Create an OCI layer",
+		Long:  `Create an OCI layer based on the changeset between filesystems.`,
+		Run:   v.Run,
+	}
+	cmd.Flags().StringVar(
+		&v.dest, "dest", "",
+		`The dest specify a particular filename where the layer write to`,
+	)
+	return cmd
+}
+
+func (v *layerCmd) Run(cmd *cobra.Command, args []string) {
+	if len(args) != 1 && len(args) != 2 {
+		v.stderr.Print("One or two filesystems are required")
+		if err := cmd.Usage(); err != nil {
+			v.stderr.Println(err)
+		}
+		os.Exit(1)
+	}
+	var err error
+	if len(args) == 1 {
+		err = image.CreateLayer(args[0], "", v.dest)
+	} else {
+		err = image.CreateLayer(args[0], args[1], v.dest)
+	}
+	if err != nil {
+		v.stderr.Printf("create layer failed: %v", err)
+		os.Exit(1)
+	}
+	os.Exit(0)
+}

image/change.go

@@ -0,0 +1,283 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 image
+
+import (
+	"archive/tar"
+	"bytes"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/opencontainers/image-tools/utils"
+)
+
+// ChangeType represents the change type.
+type ChangeType int
+
+const (
+	// ChangeModify represents the modify operation.
+	ChangeModify = iota
+	// ChangeAdd represents the add operation.
+	ChangeAdd
+	// ChangeDelete represents the delete operation.
+	ChangeDelete
+)
+
+// Change represents a change, it wraps the change type and path.
+// It describes changes of the files in the path respect to the
+// parent layers. The change could be modify, add, delete.
+// This is used for layer diff.
+type Change struct {
+	Path string
+	Kind ChangeType
+}
+
+// for sort.Sort
+type changesByPath []Change
+
+func (c changesByPath) Less(i, j int) bool { return c[i].Path < c[j].Path }
+func (c changesByPath) Len() int           { return len(c) }
+func (c changesByPath) Swap(i, j int)      { c[j], c[i] = c[i], c[j] }
+
+// Gnu tar and the go tar writer don't have sub-second mtime
+// precision, which is problematic when we apply changes via tar
+// files, we handle this by comparing for exact times, *or* same
+// second count and either a or b having exactly 0 nanoseconds
+func sameFsTime(a, b time.Time) bool {
+	return a == b ||
+		(a.Unix() == b.Unix() &&
+			(a.Nanosecond() == 0 || b.Nanosecond() == 0))
+}
+
+func sameFsTimeSpec(a, b syscall.Timespec) bool {
+	return a.Sec == b.Sec &&
+		(a.Nsec == b.Nsec || a.Nsec == 0 || b.Nsec == 0)
+}
+
+// FileInfo describes the information of a file.
+type FileInfo struct {
+	parent     *FileInfo
+	name       string
+	stat       *utils.StatT
+	children   map[string]*FileInfo
+	capability []byte
+	added      bool
+}
+
+func newRootFileInfo() *FileInfo {
+	// As this runs on the daemon side, file paths are OS specific.
+	root := &FileInfo{
+		name:     string(os.PathSeparator),
+		children: make(map[string]*FileInfo),
+	}
+	return root
+}
+
+// LookUp looks up the file information of a file.
+func (info *FileInfo) LookUp(path string) *FileInfo {
+	// As this runs on the daemon side, file paths are OS specific.
+	parent := info
+	if path == string(os.PathSeparator) {
+		return info
+	}
+
+	pathElements := strings.Split(path, string(os.PathSeparator))
+	for _, elem := range pathElements {
+		if elem != "" {
+			child := parent.children[elem]
+			if child == nil {
+				return nil
+			}
+			parent = child
+		}
+	}
+	return parent
+}
+
+func (info *FileInfo) path() string {
+	if info.parent == nil {
+		// As this runs on the daemon side, file paths are OS specific.
+		return string(os.PathSeparator)
+	}
+	return filepath.Join(info.parent.path(), info.name)
+}
+
+func (info *FileInfo) addChanges(oldInfo *FileInfo, changes *[]Change) {
+
+	sizeAtEntry := len(*changes)
+
+	if oldInfo == nil {
+		// add
+		change := Change{
+			Path: info.path(),
+			Kind: ChangeAdd,
+		}
+		*changes = append(*changes, change)
+		info.added = true
+	}
+
+	// We make a copy so we can modify it to detect additions
+	// also, we only recurse on the old dir if the new info is a directory
+	// otherwise any previous delete/change is considered recursive
+	oldChildren := make(map[string]*FileInfo)
+	if oldInfo != nil && info.isDir() {
+		for k, v := range oldInfo.children {
+			oldChildren[k] = v
+		}
+	}
+
+	for name, newChild := range info.children {
+		oldChild, _ := oldChildren[name]
+		if oldChild != nil {
+			// change?
+			oldStat := oldChild.stat
+			newStat := newChild.stat
+			// Note: We can't compare inode or ctime or blocksize here, because these change
+			// when copying a file into a container. However, that is not generally a problem
+			// because any content change will change mtime, and any status change should
+			// be visible when actually comparing the stat fields. The only time this
+			// breaks down is if some code intentionally hides a change by setting
+			// back mtime
+			if statDifferent(oldStat, newStat) ||
+				bytes.Compare(oldChild.capability, newChild.capability) != 0 {
+				change := Change{
+					Path: newChild.path(),
+					Kind: ChangeModify,
+				}
+				*changes = append(*changes, change)
+				newChild.added = true
+			}
+
+			// Remove from copy so we can detect deletions
+			delete(oldChildren, name)
+		}
+
+		newChild.addChanges(oldChild, changes)
+	}
+	for _, oldChild := range oldChildren {
+		// delete
+		change := Change{
+			Path: oldChild.path(),
+			Kind: ChangeDelete,
+		}
+		*changes = append(*changes, change)
+	}
+
+	// If there were changes inside this directory, we need to add it, even if the directory
+	// itself wasn't changed. This is needed to properly save and restore filesystem permissions.
+	// As this runs on the daemon side, file paths are OS specific.
+	if len(*changes) > sizeAtEntry && info.isDir() && !info.added && info.path() != string(os.PathSeparator) {
+		change := Change{
+			Path: info.path(),
+			Kind: ChangeModify,
+		}
+		// Let's insert the directory entry before the recently added entries located inside this dir
+		*changes = append(*changes, change) // just to resize the slice, will be overwritten
+		copy((*changes)[sizeAtEntry+1:], (*changes)[sizeAtEntry:])
+		(*changes)[sizeAtEntry] = change
+	}
+
+}
+
+// Changes add changes to file information.
+func (info *FileInfo) Changes(oldInfo *FileInfo) []Change {
+	var changes []Change
+
+	info.addChanges(oldInfo, &changes)
+
+	return changes
+}
+
+// ChangesDirs compares two directories and generates an array of Change objects describing the changes.
+// If oldDir is "", then all files in newDir will be Add-Changes.
+func ChangesDirs(newDir, oldDir string) ([]Change, error) {
+	var (
+		oldRoot, newRoot *FileInfo
+	)
+	if oldDir == "" {
+		emptyDir, err := ioutil.TempDir("", "empty")
+		if err != nil {
+			return nil, err
+		}
+		defer os.Remove(emptyDir)
+		oldDir = emptyDir
+	}
+	oldRoot, newRoot, err := collectFileInfoForChanges(oldDir, newDir)
+	if err != nil {
+		return nil, err
+	}
+
+	return newRoot.Changes(oldRoot), nil
+}
+
+// ExportChanges produces an Archive from the provided changes, relative to dir.
+func exportChanges(dir string, changes []Change) (io.ReadCloser, error) {
+	reader, writer := io.Pipe()
+	go func() {
+		ta := &utils.TarAppender{
+			TarWriter: tar.NewWriter(writer),
+			Buffer:    utils.BufioWriter32KPool.Get(nil),
+			SeenFiles: make(map[uint64]string),
+		}
+		// this buffer is needed for the duration of this piped stream
+		defer utils.BufioWriter32KPool.Put(ta.Buffer)
+
+		sort.Sort(changesByPath(changes))
+
+		// In general we log errors here but ignore them because
+		// during e.g. a diff operation the container can continue
+		// mutating the filesystem and we can see transient errors
+		// from this
+		for _, change := range changes {
+			if change.Kind == ChangeDelete {
+				whiteOutDir := filepath.Dir(change.Path)
+				whiteOutBase := filepath.Base(change.Path)
+				whiteOut := filepath.Join(whiteOutDir, ".wh."+whiteOutBase)
+				timestamp := time.Now()
+				hdr := &tar.Header{
+					Name:       whiteOut[1:],
+					Size:       0,
+					ModTime:    timestamp,
+					AccessTime: timestamp,
+					ChangeTime: timestamp,
+				}
+				if err := ta.TarWriter.WriteHeader(hdr); err != nil {
+					logrus.Debugf("Can't write whiteout header: %s", err)
+				}
+			} else {
+				path := filepath.Join(dir, change.Path)
+				if err := ta.AddTarFile(path, change.Path[1:]); err != nil {
+					logrus.Debugf("Can't add file %s to tar: %s", path, err)
+				}
+			}
+		}
+
+		// Make sure to check the error on Close.
+		if err := ta.TarWriter.Close(); err != nil {
+			logrus.Debugf("Can't close layer: %s", err)
+		}
+		if err := writer.Close(); err != nil {
+			logrus.Debugf("failed close Changes writer: %s", err)
+		}
+	}()
+	return reader, nil
+}