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experiments with restoring dead dir #11552

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95 changes: 89 additions & 6 deletions pkg/sentry/fsimpl/gofer/save_restore.go
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Original file line number Diff line number Diff line change
Expand Up @@ -112,8 +112,8 @@ func (fd *specialFileFD) savePipeData(ctx context.Context) error {
}

func (d *dentry) prepareSaveDead(ctx context.Context) error {
if !d.isRegularFile() {
return fmt.Errorf("gofer.dentry(%q).prepareSaveDead: only regular deleted dentries can be saved, got %s", genericDebugPathname(d.fs, d), linux.FileMode(d.mode.Load()))
if !d.isRegularFile() && !d.isDir() {
return fmt.Errorf("gofer.dentry(%q).prepareSaveDead: only regular or directory deleted dentries can be saved, got %s", genericDebugPathname(d.fs, d), linux.FileMode(d.mode.Load()))
}
if !d.isDeleted() {
return fmt.Errorf("gofer.dentry(%q).prepareSaveDead: invalidated dentries can't be saved", genericDebugPathname(d.fs, d))
Expand All @@ -129,6 +129,17 @@ func (d *dentry) prepareSaveDead(ctx context.Context) error {
write: d.isWriteHandleOk(),
}
}

// Directory case - no need to store the data, just mark as saved
if d.isDir() {
if d.fs.savedDeletedOpenDentries == nil {
d.fs.savedDeletedOpenDentries = make(map[*dentry]struct{})
}
d.fs.savedDeletedOpenDentries[d] = struct{}{}
return nil
}

// Regular file case
d.handleMu.RLock()
defer d.handleMu.RUnlock()
var h handle
Expand Down Expand Up @@ -200,7 +211,7 @@ func (d *dentry) prepareSaveRecursive(ctx context.Context) error {

// beforeSave is invoked by stateify.
func (d *dentry) beforeSave() {
if d.vfsd.IsDead() && d.deletedDataSR == nil {
if d.vfsd.IsDead() && d.deletedDataSR == nil && !d.isDir() {
panic(fmt.Sprintf("gofer.dentry(%q).beforeSave: deletedDataSR is nil for dead dentry (deleted=%t, synthetic=%t)", genericDebugPathname(d.fs, d), d.isDeleted(), d.isSynthetic()))
}
}
Expand Down Expand Up @@ -344,12 +355,84 @@ func (d *dentry) restoreDescendantsRecursive(ctx context.Context, opts *vfs.Comp
return nil
}

// restoreDead restores a deleted regular file.
// verifyParentPath checks if the parent path exists and is accessible
func verifyParentPath(ctx context.Context, parent *dentry) error {
if parent == nil {
return fmt.Errorf("parent is nil")
}

// Check if parent's parent is accessible if not root
if parent != parent.fs.root {
parentParent := parent.parent.Load()
if parentParent == nil {
return fmt.Errorf("parent's parent is nil and not root")
}
}

// Verify parent is a directory
if !parent.isDir() {
return fmt.Errorf("parent is not a directory")
}

return nil
}

// restoreDead restores a deleted regular file or directory.
//
// Preconditions: d.deletedDataSR != nil.
// Preconditions: For regular files, d.deletedDataSR != nil.
func (d *dentry) restoreDead(ctx context.Context, opts *vfs.CompleteRestoreOptions) error {
// Recreate the file on the host filesystem (this is temporary).
parent := d.parent.Load()
if parent == nil {
return fmt.Errorf("cannot restore %q: parent is nil", genericDebugPathname(d.fs, d))
}

// Handle directory case
if d.isDir() {
// Make sure the parent path exists and is accessible
if err := verifyParentPath(ctx, parent); err != nil {
return fmt.Errorf("failed to verify parent path for %q: %w", genericDebugPathname(d.fs, d), err)
}

log.Debugf("Recreating deleted directory %q in parent %q", d.name, genericDebugPathname(d.fs, parent))

// Recreate the directory on the host filesystem
_, err := parent.mkdir(ctx, d.name, linux.FileMode(d.mode.Load()), auth.KUID(d.uid.Load()), auth.KGID(d.gid.Load()))
if err != nil {
return fmt.Errorf("failed to re-create deleted directory %q: %w", genericDebugPathname(d.fs, d), err)
}

// In case of errors, clean up the recreated directory
unlinkCU := cleanup.Make(func() {
if err := parent.unlink(ctx, d.name, linux.AT_REMOVEDIR); err != nil {
log.Warningf("failed to clean up recreated deleted directory %q: %v", genericDebugPathname(d.fs, d), err)
}
})
defer unlinkCU.Clean()

// Restore the directory
recreateOpts := *opts
recreateOpts.ValidateFileModificationTimestamps = false
if err := d.restoreFile(ctx, &recreateOpts); err != nil {
return err
}

// Finally, unlink the recreated directory
unlinkCU.Release()
if err := parent.unlink(ctx, d.name, linux.AT_REMOVEDIR); err != nil {
return fmt.Errorf("failed to clean up recreated deleted directory %q: %v", genericDebugPathname(d.fs, d), err)
}
return nil
}

// Regular file case
// Make sure the parent path exists and is accessible
if err := verifyParentPath(ctx, parent); err != nil {
return fmt.Errorf("failed to verify parent path for %q: %w", genericDebugPathname(d.fs, d), err)
}

log.Debugf("Recreating deleted file %q in parent %q", d.name, genericDebugPathname(d.fs, parent))

// Recreate the file on the host filesystem (this is temporary).
_, h, err := parent.openCreate(ctx, d.name, linux.O_WRONLY, linux.FileMode(d.mode.Load()), auth.KUID(d.uid.Load()), auth.KGID(d.gid.Load()), false /* createDentry */)
if err != nil {
return fmt.Errorf("failed to re-create deleted file %q: %w", genericDebugPathname(d.fs, d), err)
Expand Down