93 lines
2.8 KiB
Go
93 lines
2.8 KiB
Go
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package fs
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import (
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"bytes"
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"os"
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"path/filepath"
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"strings"
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"syscall"
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"github.com/pkg/errors"
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"github.com/stevvooe/continuity/sysx"
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)
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// whiteouts are files with a special meaning for the layered filesystem.
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// Docker uses AUFS whiteout files inside exported archives. In other
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// filesystems these files are generated/handled on tar creation/extraction.
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// whiteoutPrefix prefix means file is a whiteout. If this is followed by a
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// filename this means that file has been removed from the base layer.
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const whiteoutPrefix = ".wh."
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// whiteoutMetaPrefix prefix means whiteout has a special meaning and is not
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// for removing an actual file. Normally these files are excluded from exported
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// archives.
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const whiteoutMetaPrefix = whiteoutPrefix + whiteoutPrefix
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// whiteoutLinkDir is a directory AUFS uses for storing hardlink links to other
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// layers. Normally these should not go into exported archives and all changed
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// hardlinks should be copied to the top layer.
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const whiteoutLinkDir = whiteoutMetaPrefix + "plnk"
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// whiteoutOpaqueDir file means directory has been made opaque - meaning
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// readdir calls to this directory do not follow to lower layers.
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const whiteoutOpaqueDir = whiteoutMetaPrefix + ".opq"
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// detectDirDiff returns diff dir options if a directory could
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// be found in the mount info for upper which is the direct
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// diff with the provided lower directory
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func detectDirDiff(upper, lower string) *diffDirOptions {
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// TODO: get mount options for upper
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// TODO: detect AUFS
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// TODO: detect overlay
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return nil
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}
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func aufsMetadataSkip(path string) (skip bool, err error) {
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skip, err = filepath.Match(string(os.PathSeparator)+whiteoutMetaPrefix+"*", path)
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if err != nil {
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skip = true
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}
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return
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}
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func aufsDeletedFile(root, path string, fi os.FileInfo) (string, error) {
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f := filepath.Base(path)
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// If there is a whiteout, then the file was removed
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if strings.HasPrefix(f, whiteoutPrefix) {
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originalFile := f[len(whiteoutPrefix):]
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return filepath.Join(filepath.Dir(path), originalFile), nil
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}
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return "", nil
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}
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// compareSysStat returns whether the stats are equivalent,
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// whether the files are considered the same file, and
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// an error
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func compareSysStat(s1, s2 interface{}) (bool, error) {
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ls1, ok := s1.(*syscall.Stat_t)
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if !ok {
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return false, nil
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}
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ls2, ok := s2.(*syscall.Stat_t)
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if !ok {
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return false, nil
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}
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return ls1.Mode == ls2.Mode && ls1.Uid == ls2.Uid && ls1.Gid == ls2.Gid && ls1.Rdev == ls2.Rdev, nil
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}
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func compareCapabilities(p1, p2 string) (bool, error) {
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c1, err := sysx.LGetxattr(p1, "security.capability")
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if err != nil && err != syscall.ENODATA {
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return false, errors.Wrapf(err, "failed to get xattr for %s", p1)
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}
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c2, err := sysx.LGetxattr(p2, "security.capability")
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if err != nil && err != syscall.ENODATA {
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return false, errors.Wrapf(err, "failed to get xattr for %s", p2)
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}
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return bytes.Equal(c1, c2), nil
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}
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