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diffapply_unix.go
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diffapply_unix.go
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//go:build !windows
// +build !windows
package snapshot
import (
"context"
gofs "io/fs"
"os"
"path/filepath"
"strings"
"syscall"
"github.com/containerd/containerd/leases"
"github.com/containerd/containerd/mount"
"github.com/containerd/containerd/snapshots"
"github.com/containerd/containerd/snapshots/overlay/overlayutils"
"github.com/containerd/continuity/fs"
"github.com/containerd/continuity/sysx"
"github.com/hashicorp/go-multierror"
"github.com/moby/buildkit/identity"
"github.com/moby/buildkit/util/bklog"
"github.com/moby/buildkit/util/leaseutil"
"github.com/moby/buildkit/util/overlay"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
)
// diffApply applies the provided diffs to the dest Mountable and returns the correctly calculated disk usage
// that accounts for any hardlinks made from existing snapshots. ctx is expected to have a temporary lease
// associated with it.
func (sn *mergeSnapshotter) diffApply(ctx context.Context, dest Mountable, diffs ...Diff) (_ snapshots.Usage, rerr error) {
a, err := applierFor(dest, sn.tryCrossSnapshotLink, sn.userxattr)
if err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to create applier")
}
defer func() {
releaseErr := a.Release()
if releaseErr != nil {
rerr = multierror.Append(rerr, errors.Wrapf(releaseErr, "failed to release applier")).ErrorOrNil()
}
}()
// TODO:(sipsma) optimization: parallelize differ and applier in separate goroutines, connected with a buffered channel
for _, diff := range diffs {
var lowerMntable Mountable
if diff.Lower != "" {
if info, err := sn.Stat(ctx, diff.Lower); err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to stat lower snapshot %s", diff.Lower)
} else if info.Kind == snapshots.KindCommitted {
lowerMntable, err = sn.View(ctx, identity.NewID(), diff.Lower)
if err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to mount lower snapshot view %s", diff.Lower)
}
} else {
lowerMntable, err = sn.Mounts(ctx, diff.Lower)
if err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to mount lower snapshot %s", diff.Lower)
}
}
}
var upperMntable Mountable
if diff.Upper != "" {
if info, err := sn.Stat(ctx, diff.Upper); err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to stat upper snapshot %s", diff.Upper)
} else if info.Kind == snapshots.KindCommitted {
upperMntable, err = sn.View(ctx, identity.NewID(), diff.Upper)
if err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to mount upper snapshot view %s", diff.Upper)
}
} else {
upperMntable, err = sn.Mounts(ctx, diff.Upper)
if err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to mount upper snapshot %s", diff.Upper)
}
}
} else {
// create an empty view
upperMntable, err = sn.View(ctx, identity.NewID(), "")
if err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to mount empty upper snapshot view %s", diff.Upper)
}
}
d, err := differFor(lowerMntable, upperMntable)
if err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to create differ")
}
defer func() {
rerr = multierror.Append(rerr, d.Release()).ErrorOrNil()
}()
if err := d.HandleChanges(ctx, a.Apply); err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to handle changes")
}
}
if err := a.Flush(); err != nil {
return snapshots.Usage{}, errors.Wrapf(err, "failed to flush changes")
}
return a.Usage()
}
type change struct {
kind fs.ChangeKind
subPath string
srcPath string
srcStat *syscall.Stat_t
// linkSubPath is set to a subPath of a previous change from the same
// differ instance that is a hardlink to this one, if any.
linkSubPath string
}
type changeApply struct {
*change
dstPath string
dstStat *syscall.Stat_t
setOpaque bool
}
type inode struct {
ino uint64
dev uint64
}
func statInode(stat *syscall.Stat_t) inode {
if stat == nil {
return inode{}
}
return inode{
ino: stat.Ino,
dev: stat.Dev,
}
}
type applier struct {
root string
release func() error
lowerdirs []string // ordered highest -> lowest, the order we want to check them in
crossSnapshotLinks map[inode]struct{}
createWhiteoutDelete bool
userxattr bool
dirModTimes map[string]unix.Timespec // map of dstPath -> mtime that should be set on that subPath
}
func applierFor(dest Mountable, tryCrossSnapshotLink, userxattr bool) (_ *applier, rerr error) {
a := &applier{
dirModTimes: make(map[string]unix.Timespec),
userxattr: userxattr,
}
defer func() {
if rerr != nil {
rerr = multierror.Append(rerr, a.Release()).ErrorOrNil()
}
}()
if tryCrossSnapshotLink {
a.crossSnapshotLinks = make(map[inode]struct{})
}
mnts, release, err := dest.Mount()
if err != nil {
return nil, nil
}
a.release = release
if len(mnts) != 1 {
return nil, errors.Errorf("expected exactly one mount, got %d", len(mnts))
}
mnt := mnts[0]
if overlay.IsOverlayMountType(mnt) {
for _, opt := range mnt.Options {
if strings.HasPrefix(opt, "upperdir=") {
a.root = strings.TrimPrefix(opt, "upperdir=")
} else if strings.HasPrefix(opt, "lowerdir=") {
a.lowerdirs = strings.Split(strings.TrimPrefix(opt, "lowerdir="), ":")
}
}
if a.root == "" {
return nil, errors.Errorf("could not find upperdir in mount options %v", mnt.Options)
}
if len(a.lowerdirs) == 0 {
return nil, errors.Errorf("could not find lowerdir in mount options %v", mnt.Options)
}
a.createWhiteoutDelete = true
} else if mnt.Type == "bind" || mnt.Type == "rbind" {
a.root = mnt.Source
} else {
mnter := LocalMounter(dest)
root, err := mnter.Mount()
if err != nil {
return nil, err
}
a.root = root
prevRelease := a.release
a.release = func() error {
err := mnter.Unmount()
return multierror.Append(err, prevRelease()).ErrorOrNil()
}
}
a.root, err = filepath.EvalSymlinks(a.root)
if err != nil {
return nil, errors.Wrapf(err, "failed to resolve symlinks in %s", a.root)
}
return a, nil
}
func (a *applier) Apply(ctx context.Context, c *change) error {
if c == nil {
return errors.New("nil change")
}
if c.kind == fs.ChangeKindUnmodified {
return nil
}
dstPath, err := safeJoin(a.root, c.subPath)
if err != nil {
return errors.Wrapf(err, "failed to join paths %q and %q", a.root, c.subPath)
}
var dstStat *syscall.Stat_t
if dstfi, err := os.Lstat(dstPath); err == nil {
stat, ok := dstfi.Sys().(*syscall.Stat_t)
if !ok {
return errors.Errorf("failed to get stat_t for %T", dstStat)
}
dstStat = stat
} else if !os.IsNotExist(err) {
return errors.Wrap(err, "failed to stat during copy apply")
}
ca := &changeApply{
change: c,
dstPath: dstPath,
dstStat: dstStat,
}
if done, err := a.applyDelete(ctx, ca); err != nil {
return errors.Wrap(err, "failed to delete during apply")
} else if done {
return nil
}
if done, err := a.applyHardlink(ctx, ca); err != nil {
return errors.Wrapf(err, "failed to hardlink during apply")
} else if done {
return nil
}
if err := a.applyCopy(ctx, ca); err != nil {
return errors.Wrapf(err, "failed to copy during apply")
}
return nil
}
func (a *applier) applyDelete(ctx context.Context, ca *changeApply) (bool, error) {
// Even when not deleting, we may be overwriting a file, in which case we should
// delete the existing file at the path, if any. Don't delete when both are dirs
// in this case though because they should get merged, not overwritten.
deleteOnly := ca.kind == fs.ChangeKindDelete
overwrite := !deleteOnly && ca.dstStat != nil && ca.srcStat.Mode&ca.dstStat.Mode&unix.S_IFMT != unix.S_IFDIR
if !deleteOnly && !overwrite {
// nothing to delete, continue on
return false, nil
}
if err := os.RemoveAll(ca.dstPath); err != nil {
return false, errors.Wrap(err, "failed to remove during apply")
}
ca.dstStat = nil
if overwrite && a.createWhiteoutDelete && ca.srcStat.Mode&unix.S_IFMT == unix.S_IFDIR {
// If we are using an overlay snapshotter and overwriting an existing non-directory
// with a directory, we need this new dir to be opaque so that any files from lowerdirs
// under it are not visible.
ca.setOpaque = true
}
if deleteOnly && a.createWhiteoutDelete {
// only create a whiteout device if there is something to delete
var foundLower bool
for _, lowerdir := range a.lowerdirs {
lowerPath, err := safeJoin(lowerdir, ca.subPath)
if err != nil {
return false, errors.Wrapf(err, "failed to join lowerdir %q and subPath %q", lowerdir, ca.subPath)
}
if _, err := os.Lstat(lowerPath); err == nil {
foundLower = true
break
} else if !errors.Is(err, unix.ENOENT) && !errors.Is(err, unix.ENOTDIR) {
return false, errors.Wrapf(err, "failed to stat lowerPath %q", lowerPath)
}
}
if foundLower {
ca.kind = fs.ChangeKindAdd
if ca.srcStat == nil {
ca.srcStat = &syscall.Stat_t{
Mode: syscall.S_IFCHR,
Rdev: unix.Mkdev(0, 0),
}
ca.srcPath = ""
}
return false, nil
}
}
return deleteOnly, nil
}
func (a *applier) applyHardlink(ctx context.Context, ca *changeApply) (bool, error) {
switch ca.srcStat.Mode & unix.S_IFMT {
case unix.S_IFDIR, unix.S_IFIFO, unix.S_IFSOCK:
// Directories can't be hard-linked, so they just have to be recreated.
// Named pipes and sockets can be hard-linked but is best to avoid as it could enable IPC in weird cases.
return false, nil
default:
var linkSrcPath string
if ca.linkSubPath != "" {
// there's an already applied path that we should link from
path, err := safeJoin(a.root, ca.linkSubPath)
if err != nil {
return false, errors.Errorf("failed to get hardlink source path: %v", err)
}
linkSrcPath = path
} else if a.crossSnapshotLinks != nil {
// we can try to link across snapshots from the source file
linkSrcPath = ca.srcPath
a.crossSnapshotLinks[statInode(ca.srcStat)] = struct{}{}
}
if linkSrcPath == "" {
// nothing to hardlink from, will have to copy the file
return false, nil
}
if err := os.Link(linkSrcPath, ca.dstPath); errors.Is(err, unix.EXDEV) || errors.Is(err, unix.EMLINK) {
// These errors are expected when the hardlink would cross devices or would exceed the maximum number of links for the inode.
// Just fallback to a copy.
bklog.G(ctx).WithError(err).WithField("srcPath", linkSrcPath).WithField("dstPath", ca.dstPath).Debug("hardlink failed")
if a.crossSnapshotLinks != nil {
delete(a.crossSnapshotLinks, statInode(ca.srcStat))
}
return false, nil
} else if err != nil {
return false, errors.Wrap(err, "failed to hardlink during apply")
}
return true, nil
}
}
func (a *applier) applyCopy(ctx context.Context, ca *changeApply) error {
switch ca.srcStat.Mode & unix.S_IFMT {
case unix.S_IFREG:
if err := fs.CopyFile(ca.dstPath, ca.srcPath); err != nil {
return errors.Wrapf(err, "failed to copy from %s to %s during apply", ca.srcPath, ca.dstPath)
}
case unix.S_IFDIR:
if ca.dstStat == nil {
// dstPath doesn't exist, make it a dir
if err := unix.Mkdir(ca.dstPath, ca.srcStat.Mode); err != nil {
return errors.Wrapf(err, "failed to create applied dir at %q from %q", ca.dstPath, ca.srcPath)
}
}
case unix.S_IFLNK:
if target, err := os.Readlink(ca.srcPath); err != nil {
return errors.Wrap(err, "failed to read symlink during apply")
} else if err := os.Symlink(target, ca.dstPath); err != nil {
return errors.Wrap(err, "failed to create symlink during apply")
}
case unix.S_IFBLK, unix.S_IFCHR, unix.S_IFIFO, unix.S_IFSOCK:
if err := unix.Mknod(ca.dstPath, ca.srcStat.Mode, int(ca.srcStat.Rdev)); err != nil {
return errors.Wrap(err, "failed to mknod during apply")
}
default:
// should never be here, all types should be handled
return errors.Errorf("unhandled file type %d during merge at path %q", ca.srcStat.Mode&unix.S_IFMT, ca.srcPath)
}
// NOTE: it's important that chown happens before setting xattrs due to the fact that chown will
// reset the security.capabilities xattr which results in file capabilities being lost.
if err := os.Lchown(ca.dstPath, int(ca.srcStat.Uid), int(ca.srcStat.Gid)); err != nil {
return errors.Wrap(err, "failed to chown during apply")
}
if ca.srcStat.Mode&unix.S_IFMT != unix.S_IFLNK {
if err := unix.Chmod(ca.dstPath, ca.srcStat.Mode); err != nil {
return errors.Wrapf(err, "failed to chmod path %q during apply", ca.dstPath)
}
}
if ca.srcPath != "" {
xattrs, err := sysx.LListxattr(ca.srcPath)
if err != nil {
return errors.Wrapf(err, "failed to list xattrs of src path %s", ca.srcPath)
}
for _, xattr := range xattrs {
if isOpaqueXattr(xattr) {
// Don't recreate opaque xattrs during merge based on the source file. The differs take care of converting
// source path from the "opaque whiteout" format to the "explicit whiteout" format. The only time we set
// opaque xattrs is handled after this loop below.
continue
}
xattrVal, err := sysx.LGetxattr(ca.srcPath, xattr)
if err != nil {
return errors.Wrapf(err, "failed to get xattr %s of src path %s", xattr, ca.srcPath)
}
if err := sysx.LSetxattr(ca.dstPath, xattr, xattrVal, 0); err != nil {
// This can often fail, so just log it: https://github.com/moby/buildkit/issues/1189
bklog.G(ctx).Debugf("failed to set xattr %s of path %s during apply", xattr, ca.dstPath)
}
}
}
if ca.setOpaque {
// This is set in the case where we are creating a directory that is replacing a whiteout device
xattr := opaqueXattr(a.userxattr)
if err := sysx.LSetxattr(ca.dstPath, xattr, []byte{'y'}, 0); err != nil {
return errors.Wrapf(err, "failed to set opaque xattr %q of path %s", xattr, ca.dstPath)
}
}
atimeSpec := unix.Timespec{Sec: ca.srcStat.Atim.Sec, Nsec: ca.srcStat.Atim.Nsec}
mtimeSpec := unix.Timespec{Sec: ca.srcStat.Mtim.Sec, Nsec: ca.srcStat.Mtim.Nsec}
if ca.srcStat.Mode&unix.S_IFMT != unix.S_IFDIR {
// apply times immediately for non-dirs
if err := unix.UtimesNanoAt(unix.AT_FDCWD, ca.dstPath, []unix.Timespec{atimeSpec, mtimeSpec}, unix.AT_SYMLINK_NOFOLLOW); err != nil {
return err
}
} else {
// save the times we should set on this dir, to be applied after subfiles have been set
a.dirModTimes[ca.dstPath] = mtimeSpec
}
return nil
}
func (a *applier) Flush() error {
// Set dir times now that everything has been modified. Walk the filesystem tree to ensure
// that we never try to apply to a path that has been deleted or modified since times for it
// were stored. This is needed for corner cases such as where a parent dir is removed and
// replaced with a symlink.
return filepath.WalkDir(a.root, func(path string, d gofs.DirEntry, prevErr error) error {
if prevErr != nil {
return prevErr
}
if !d.IsDir() {
return nil
}
if mtime, ok := a.dirModTimes[path]; ok {
if err := unix.UtimesNanoAt(unix.AT_FDCWD, path, []unix.Timespec{{Nsec: unix.UTIME_OMIT}, mtime}, unix.AT_SYMLINK_NOFOLLOW); err != nil {
return err
}
}
return nil
})
}
func (a *applier) Release() error {
if a.release != nil {
err := a.release()
if err != nil {
return err
}
}
a.release = nil
return nil
}
func (a *applier) Usage() (snapshots.Usage, error) {
// Calculate the disk space used under the apply root, similar to the normal containerd snapshotter disk usage
// calculations but with the extra ability to take into account hardlinks that were created between snapshots, ensuring that
// they don't get double counted.
inodes := make(map[inode]struct{})
var usage snapshots.Usage
if err := filepath.WalkDir(a.root, func(path string, dirent gofs.DirEntry, err error) error {
if err != nil {
return err
}
info, err := dirent.Info()
if err != nil {
return err
}
stat := info.Sys().(*syscall.Stat_t)
inode := statInode(stat)
if _, ok := inodes[inode]; ok {
return nil
}
inodes[inode] = struct{}{}
if a.crossSnapshotLinks != nil {
if _, ok := a.crossSnapshotLinks[statInode(stat)]; ok {
// don't count cross-snapshot hardlinks
return nil
}
}
usage.Inodes++
usage.Size += stat.Blocks * 512 // 512 is always block size, see "man 2 stat"
return nil
}); err != nil {
return snapshots.Usage{}, err
}
return usage, nil
}
type differ struct {
lowerRoot string
releaseLower func() error
upperRoot string
releaseUpper func() error
upperBindSource string
upperOverlayDirs []string // ordered lowest -> highest
upperdir string
visited map[string]struct{} // set of parent subPaths that have been visited
inodes map[inode]string // map of inode -> subPath
}
func differFor(lowerMntable, upperMntable Mountable) (_ *differ, rerr error) {
d := &differ{
visited: make(map[string]struct{}),
inodes: make(map[inode]string),
}
defer func() {
if rerr != nil {
rerr = multierror.Append(rerr, d.Release()).ErrorOrNil()
}
}()
var lowerMnts []mount.Mount
if lowerMntable != nil {
mnts, release, err := lowerMntable.Mount()
if err != nil {
return nil, err
}
mounter := LocalMounterWithMounts(mnts)
root, err := mounter.Mount()
if err != nil {
return nil, err
}
d.lowerRoot = root
lowerMnts = mnts
d.releaseLower = func() error {
err := mounter.Unmount()
return multierror.Append(err, release()).ErrorOrNil()
}
}
var upperMnts []mount.Mount
if upperMntable != nil {
mnts, release, err := upperMntable.Mount()
if err != nil {
return nil, err
}
mounter := LocalMounterWithMounts(mnts)
root, err := mounter.Mount()
if err != nil {
return nil, err
}
d.upperRoot = root
upperMnts = mnts
d.releaseUpper = func() error {
err := mounter.Unmount()
return multierror.Append(err, release()).ErrorOrNil()
}
}
if len(upperMnts) == 1 {
if upperMnts[0].Type == "bind" || upperMnts[0].Type == "rbind" {
d.upperBindSource = upperMnts[0].Source
} else if overlay.IsOverlayMountType(upperMnts[0]) {
overlayDirs, err := overlay.GetOverlayLayers(upperMnts[0])
if err != nil {
return nil, errors.Wrapf(err, "failed to get overlay layers from mount %+v", upperMnts[0])
}
d.upperOverlayDirs = overlayDirs
}
}
if len(lowerMnts) > 0 {
if upperdir, err := overlay.GetUpperdir(lowerMnts, upperMnts); err == nil {
d.upperdir = upperdir
}
}
return d, nil
}
func (d *differ) HandleChanges(ctx context.Context, handle func(context.Context, *change) error) error {
if d.upperdir != "" {
return d.overlayChanges(ctx, handle)
}
return d.doubleWalkingChanges(ctx, handle)
}
func (d *differ) doubleWalkingChanges(ctx context.Context, handle func(context.Context, *change) error) error {
return fs.Changes(ctx, d.lowerRoot, d.upperRoot, func(kind fs.ChangeKind, subPath string, srcfi os.FileInfo, prevErr error) error {
if prevErr != nil {
return prevErr
}
if ctx.Err() != nil {
return ctx.Err()
}
if kind == fs.ChangeKindUnmodified {
return nil
}
// NOTE: it's tempting to skip creating parent dirs when change kind is Delete, but
// that would make us incompatible with the image exporter code:
// https://github.com/containerd/containerd/pull/2095
if err := d.checkParent(ctx, subPath, handle); err != nil {
return errors.Wrapf(err, "failed to check parent for %s", subPath)
}
c := &change{
kind: kind,
subPath: subPath,
}
if srcfi != nil {
// Try to ensure that srcPath and srcStat are set to a file from the underlying filesystem
// rather than the actual mount when possible. This allows hardlinking without getting EXDEV.
switch {
case !srcfi.IsDir() && d.upperBindSource != "":
srcPath, err := safeJoin(d.upperBindSource, c.subPath)
if err != nil {
return errors.Wrapf(err, "failed to join %s and %s", d.upperBindSource, c.subPath)
}
c.srcPath = srcPath
if fi, err := os.Lstat(c.srcPath); err == nil {
srcfi = fi
} else {
return errors.Wrap(err, "failed to stat underlying file from bind mount")
}
case !srcfi.IsDir() && len(d.upperOverlayDirs) > 0:
for i := range d.upperOverlayDirs {
dir := d.upperOverlayDirs[len(d.upperOverlayDirs)-1-i]
path, err := safeJoin(dir, c.subPath)
if err != nil {
return errors.Wrapf(err, "failed to join %s and %s", dir, c.subPath)
}
if stat, err := os.Lstat(path); err == nil {
c.srcPath = path
srcfi = stat
break
} else if errors.Is(err, unix.ENOENT) {
continue
} else {
return errors.Wrap(err, "failed to lstat when finding direct path of overlay file")
}
}
default:
srcPath, err := safeJoin(d.upperRoot, subPath)
if err != nil {
return errors.Wrapf(err, "failed to join %s and %s", d.upperRoot, subPath)
}
c.srcPath = srcPath
if fi, err := os.Lstat(c.srcPath); err == nil {
srcfi = fi
} else {
return errors.Wrap(err, "failed to stat srcPath from differ")
}
}
var ok bool
c.srcStat, ok = srcfi.Sys().(*syscall.Stat_t)
if !ok {
return errors.Errorf("unhandled stat type for %+v", srcfi)
}
if !srcfi.IsDir() && c.srcStat.Nlink > 1 {
if linkSubPath, ok := d.inodes[statInode(c.srcStat)]; ok {
c.linkSubPath = linkSubPath
} else {
d.inodes[statInode(c.srcStat)] = c.subPath
}
}
}
return handle(ctx, c)
})
}
func (d *differ) overlayChanges(ctx context.Context, handle func(context.Context, *change) error) error {
return overlay.Changes(ctx, func(kind fs.ChangeKind, subPath string, srcfi os.FileInfo, prevErr error) error {
if prevErr != nil {
return prevErr
}
if ctx.Err() != nil {
return ctx.Err()
}
if kind == fs.ChangeKindUnmodified {
return nil
}
if err := d.checkParent(ctx, subPath, handle); err != nil {
return errors.Wrapf(err, "failed to check parent for %s", subPath)
}
srcPath, err := safeJoin(d.upperdir, subPath)
if err != nil {
return errors.Wrapf(err, "failed to join %s and %s", d.upperdir, subPath)
}
c := &change{
kind: kind,
subPath: subPath,
srcPath: srcPath,
}
if srcfi != nil {
var ok bool
c.srcStat, ok = srcfi.Sys().(*syscall.Stat_t)
if !ok {
return errors.Errorf("unhandled stat type for %+v", srcfi)
}
if !srcfi.IsDir() && c.srcStat.Nlink > 1 {
if linkSubPath, ok := d.inodes[statInode(c.srcStat)]; ok {
c.linkSubPath = linkSubPath
} else {
d.inodes[statInode(c.srcStat)] = c.subPath
}
}
}
return handle(ctx, c)
}, d.upperdir, d.upperRoot, d.lowerRoot)
}
func (d *differ) checkParent(ctx context.Context, subPath string, handle func(context.Context, *change) error) error {
parentSubPath := filepath.Dir(subPath)
if parentSubPath == "/" {
return nil
}
if _, ok := d.visited[parentSubPath]; ok {
return nil
}
d.visited[parentSubPath] = struct{}{}
if err := d.checkParent(ctx, parentSubPath, handle); err != nil {
return err
}
parentSrcPath, err := safeJoin(d.upperRoot, parentSubPath)
if err != nil {
return err
}
srcfi, err := os.Lstat(parentSrcPath)
if err != nil {
return err
}
parentSrcStat, ok := srcfi.Sys().(*syscall.Stat_t)
if !ok {
return errors.Errorf("unexpected type %T", srcfi)
}
return handle(ctx, &change{
kind: fs.ChangeKindModify,
subPath: parentSubPath,
srcPath: parentSrcPath,
srcStat: parentSrcStat,
})
}
func (d *differ) Release() error {
var err error
if d.releaseLower != nil {
err = d.releaseLower()
if err == nil {
d.releaseLower = nil
}
}
if d.releaseUpper != nil {
err = multierror.Append(err, d.releaseUpper()).ErrorOrNil()
if err == nil {
d.releaseUpper = nil
}
}
return err
}
func safeJoin(root, path string) (string, error) {
dir, base := filepath.Split(path)
parent, err := fs.RootPath(root, dir)
if err != nil {
return "", err
}
return filepath.Join(parent, base), nil
}
const (
trustedOpaqueXattr = "trusted.overlay.opaque"
userOpaqueXattr = "user.overlay.opaque"
)
func isOpaqueXattr(s string) bool {
for _, k := range []string{trustedOpaqueXattr, userOpaqueXattr} {
if s == k {
return true
}
}
return false
}
func opaqueXattr(userxattr bool) string {
if userxattr {
return userOpaqueXattr
}
return trustedOpaqueXattr
}
// needsUserXAttr checks whether overlay mounts should be provided the userxattr option. We can't use
// NeedsUserXAttr from the overlayutils package directly because we don't always have direct knowledge
// of the root of the snapshotter state (such as when using a remote snapshotter). Instead, we create
// a temporary new snapshot and test using its root, which works because single layer snapshots will
// use bind-mounts even when created by an overlay based snapshotter.
func needsUserXAttr(ctx context.Context, sn Snapshotter, lm leases.Manager) (bool, error) {
key := identity.NewID()
ctx, done, err := leaseutil.WithLease(ctx, lm, leaseutil.MakeTemporary)
if err != nil {
return false, errors.Wrap(err, "failed to create lease for checking user xattr")
}
defer done(context.TODO())
err = sn.Prepare(ctx, key, "")
if err != nil {
return false, err
}
mntable, err := sn.Mounts(ctx, key)
if err != nil {
return false, err
}
mnts, unmount, err := mntable.Mount()
if err != nil {
return false, err
}
defer unmount()
var userxattr bool
if err := mount.WithTempMount(ctx, mnts, func(root string) error {
var err error
userxattr, err = overlayutils.NeedsUserXAttr(root)
return err
}); err != nil {
return false, err
}
return userxattr, nil
}