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- package archive
- import (
- "archive/tar"
- "os"
- "path/filepath"
- "strings"
- "syscall"
- "github.com/docker/docker/pkg/system"
- )
- func getWhiteoutConverter(format WhiteoutFormat) tarWhiteoutConverter {
- if format == OverlayWhiteoutFormat {
- return overlayWhiteoutConverter{}
- }
- return nil
- }
- type overlayWhiteoutConverter struct{}
- func (overlayWhiteoutConverter) ConvertWrite(hdr *tar.Header, path string, fi os.FileInfo) (wo *tar.Header, err error) {
- // convert whiteouts to AUFS format
- if fi.Mode()&os.ModeCharDevice != 0 && hdr.Devmajor == 0 && hdr.Devminor == 0 {
- // we just rename the file and make it normal
- dir, filename := filepath.Split(hdr.Name)
- hdr.Name = filepath.Join(dir, WhiteoutPrefix+filename)
- hdr.Mode = 0600
- hdr.Typeflag = tar.TypeReg
- hdr.Size = 0
- }
- if fi.Mode()&os.ModeDir != 0 {
- // convert opaque dirs to AUFS format by writing an empty file with the prefix
- opaque, err := system.Lgetxattr(path, "trusted.overlay.opaque")
- if err != nil {
- return nil, err
- }
- if len(opaque) == 1 && opaque[0] == 'y' {
- if hdr.Xattrs != nil {
- delete(hdr.Xattrs, "trusted.overlay.opaque")
- }
- // create a header for the whiteout file
- // it should inherit some properties from the parent, but be a regular file
- wo = &tar.Header{
- Typeflag: tar.TypeReg,
- Mode: hdr.Mode & int64(os.ModePerm),
- Name: filepath.Join(hdr.Name, WhiteoutOpaqueDir),
- Size: 0,
- Uid: hdr.Uid,
- Uname: hdr.Uname,
- Gid: hdr.Gid,
- Gname: hdr.Gname,
- AccessTime: hdr.AccessTime,
- ChangeTime: hdr.ChangeTime,
- }
- }
- }
- return
- }
- func (overlayWhiteoutConverter) ConvertRead(hdr *tar.Header, path string) (bool, error) {
- base := filepath.Base(path)
- dir := filepath.Dir(path)
- // if a directory is marked as opaque by the AUFS special file, we need to translate that to overlay
- if base == WhiteoutOpaqueDir {
- err := syscall.Setxattr(dir, "trusted.overlay.opaque", []byte{'y'}, 0)
- // don't write the file itself
- return false, err
- }
- // if a file was deleted and we are using overlay, we need to create a character device
- if strings.HasPrefix(base, WhiteoutPrefix) {
- originalBase := base[len(WhiteoutPrefix):]
- originalPath := filepath.Join(dir, originalBase)
- if err := syscall.Mknod(originalPath, syscall.S_IFCHR, 0); err != nil {
- return false, err
- }
- if err := os.Chown(originalPath, hdr.Uid, hdr.Gid); err != nil {
- return false, err
- }
- // don't write the file itself
- return false, nil
- }
- return true, nil
- }
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