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Update archive package to support overlay whiteouts

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Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
This commit is contained in:
Derek McGowan 2016-04-06 15:07:29 -07:00
parent 60dbea6c25
commit 9bb13f8f51
5 changed files with 200 additions and 78 deletions
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109
archive/archive.go
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@ -33,6 +33,8 @@ type (
Reader io.Reader
// Compression is the state represents if compressed or not.
Compression int
// WhiteoutFormat is the format of whiteouts unpacked
WhiteoutFormat int
// TarChownOptions wraps the chown options UID and GID.
TarChownOptions struct {
UID, GID int
@ -47,9 +49,10 @@ type (
GIDMaps []idtools.IDMap
ChownOpts *TarChownOptions
IncludeSourceDir bool
// When unpacking convert whiteouts and opaque dirs from aufs format to overlayfs format
// When packing convert whiteouts and opaque dirs from overlayfs format to aufs format
OverlayFormat bool
// WhiteoutFormat is the expected on disk format for whiteout files.
// This format will be converted to the standard format on pack
// and from the standard format on unpack.
WhiteoutFormat WhiteoutFormat
// When unpacking, specifies whether overwriting a directory with a
// non-directory is allowed and vice versa.
NoOverwriteDirNonDir bool
@ -96,6 +99,14 @@ const (
Xz
)
const (
// AUFSWhiteoutFormat is the default format for whitesouts
AUFSWhiteoutFormat WhiteoutFormat = iota
// OverlayWhiteoutFormat formats whiteout according to the overlay
// standard.
OverlayWhiteoutFormat
)
// IsArchive checks for the magic bytes of a tar or any supported compression
// algorithm.
func IsArchive(header []byte) bool {
@ -231,6 +242,11 @@ func (compression *Compression) Extension() string {
return ""
}
type tarWhiteoutConverter interface {
ConvertWrite(*tar.Header, string, os.FileInfo) error
ConvertRead(*tar.Header, string) (bool, error)
}
type tarAppender struct {
TarWriter *tar.Writer
Buffer *bufio.Writer
@ -240,10 +256,11 @@ type tarAppender struct {
UIDMaps []idtools.IDMap
GIDMaps []idtools.IDMap
// `overlayFormat` controls whether to interpret character devices with numbers 0,0
// and directories with the attribute `trusted.overlay.opaque` using their overlayfs
// meanings and remap them to AUFS format
OverlayFormat bool
// For packing and unpacking whiteout files in the
// non standard format. The whiteout files defined
// by the AUFS standard are used as the tar whiteout
// standard.
WhiteoutConverter tarWhiteoutConverter
}
// canonicalTarName provides a platform-independent and consistent posix-style
@ -332,13 +349,9 @@ func (ta *tarAppender) addTarFile(path, name string) error {
hdr.Gid = xGID
}
if ta.OverlayFormat {
// 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
hdr.Name = WhiteoutPrefix + hdr.Name
hdr.Mode = 0600
hdr.Typeflag = tar.TypeReg
if ta.WhiteoutConverter != nil {
if err := ta.WhiteoutConverter.ConvertWrite(hdr, path, fi); err != nil {
return err
}
}
@ -365,30 +378,6 @@ func (ta *tarAppender) addTarFile(path, name string) error {
}
}
if ta.OverlayFormat {
// convert opaque dirs to AUFS format by writing an empty file with the prefix
opaque, _ := system.Lgetxattr(path, "trusted.overlay.opaque")
if opaque != nil && len(opaque) == 1 && opaque[0] == 'y' {
// create a header for the whiteout file
// it should inherit some properties from the parent, but be a regular file
whHdr := &tar.Header{
Typeflag: tar.TypeReg,
Mode: hdr.Mode & int64(os.ModePerm),
Name: filepath.Join(name, WhiteoutOpaqueDir),
Size: 0,
Uid: hdr.Uid,
Uname: hdr.Uname,
Gid: hdr.Gid,
Gname: hdr.Gname,
AccessTime: hdr.AccessTime,
ChangeTime: hdr.ChangeTime,
}
if err := ta.TarWriter.WriteHeader(whHdr); err != nil {
return err
}
}
}
return nil
}
@ -544,12 +533,12 @@ func TarWithOptions(srcPath string, options *TarOptions) (io.ReadCloser, error)
go func() {
ta := &tarAppender{
TarWriter: tar.NewWriter(compressWriter),
Buffer: pools.BufioWriter32KPool.Get(nil),
SeenFiles: make(map[uint64]string),
UIDMaps: options.UIDMaps,
GIDMaps: options.GIDMaps,
OverlayFormat: options.OverlayFormat,
TarWriter: tar.NewWriter(compressWriter),
Buffer: pools.BufioWriter32KPool.Get(nil),
SeenFiles: make(map[uint64]string),
UIDMaps: options.UIDMaps,
GIDMaps: options.GIDMaps,
WhiteoutConverter: getWhiteoutConverter(options.WhiteoutFormat),
}
defer func() {
@ -711,6 +700,7 @@ func Unpack(decompressedArchive io.Reader, dest string, options *TarOptions) err
if err != nil {
return err
}
whiteoutConverter := getWhiteoutConverter(options.WhiteoutFormat)
// Iterate through the files in the archive.
loop:
@ -810,33 +800,12 @@ loop:
hdr.Gid = xGID
}
base := filepath.Base(path)
dir := filepath.Dir(path)
if options.OverlayFormat {
// if a directory is marked as opaque by the AUFS special file, we need to translate that to overlay
if base == WhiteoutOpaqueDir {
if err := syscall.Setxattr(dir, "trusted.overlay.opaque", []byte{'y'}, 0); err != nil {
return err
}
// don't write the file itself
continue
if whiteoutConverter != nil {
writeFile, err := whiteoutConverter.ConvertRead(hdr, path)
if err != nil {
return 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 err
}
if err := os.Chown(originalPath, hdr.Uid, hdr.Gid); err != nil {
return err
}
// don't write the file itself
if !writeFile {
continue
}
}