snapshot/overlay: port overlay driver to Snapshotter
With the change to the snapshotter interface, we've now updated the overlay driver to follow the conventions of the current test suite. To support key unification, an hashed index was added to active and committed directories. We still need to do some testing around collisions, but we'll leave that for a future PR. Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day
parent
ab08944aa7
commit
e6c1bb0ff2
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@ -9,33 +9,98 @@ import (
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"sync"
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"github.com/docker/containerd"
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"github.com/docker/containerd/snapshot"
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digest "github.com/opencontainers/go-digest"
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"github.com/pkg/errors"
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)
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type Driver struct {
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type Snapshotter struct {
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root string
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cache *cache
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links *cache
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}
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func NewDriver(root string) (*Driver, error) {
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func NewSnapshotter(root string) (*Snapshotter, error) {
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if err := os.MkdirAll(root, 0700); err != nil {
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return nil, err
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}
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for _, p := range []string{
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"snapshots",
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"active",
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"committed", // committed snapshots
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"active", // active snapshots
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"index", // snapshots by hashed name
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} {
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if err := os.MkdirAll(filepath.Join(root, p), 0700); err != nil {
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return nil, err
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}
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}
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return &Driver{
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return &Snapshotter{
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root: root,
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cache: newCache(),
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links: newCache(),
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}, nil
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}
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func (o *Driver) Prepare(key, parent string) ([]containerd.Mount, error) {
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// Stat returns the info for an active or committed snapshot by name or
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// key.
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//
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// Should be used for parent resolution, existence checks and to discern
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// the kind of snapshot.
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func (o *Snapshotter) Stat(key string) (snapshot.Info, error) {
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path, err := o.links.get(filepath.Join(o.root, "index", hash(key)))
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if err != nil {
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if !os.IsNotExist(err) {
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return snapshot.Info{}, err
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}
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return snapshot.Info{}, errors.Errorf("snapshot %v not found", key)
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}
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// TODO(stevvooe): We don't confirm the name to avoid the lookup cost.
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return o.stat(path)
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}
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func (o *Snapshotter) stat(path string) (snapshot.Info, error) {
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ppath, err := o.links.get(filepath.Join(path, "parent"))
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if err != nil {
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if !os.IsNotExist(err) {
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return snapshot.Info{}, err
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}
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// no parent
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}
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kp, err := ioutil.ReadFile(filepath.Join(path, "name"))
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if err != nil {
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return snapshot.Info{}, err
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}
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var parent string
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if ppath != "" {
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p, err := ioutil.ReadFile(filepath.Join(ppath, "name"))
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if err != nil {
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return snapshot.Info{}, err
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}
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parent = string(p)
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}
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ro := true
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kind := snapshot.KindCommitted
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if strings.HasPrefix(path, filepath.Join(o.root, "active")) {
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// TODO(stevvooe): Maybe there is a better way?
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kind = snapshot.KindActive
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// TODO(stevvooe): We haven't introduced this to overlay yet.
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// We'll add it when we add tests for it.
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ro = false
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}
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return snapshot.Info{
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Name: string(kp),
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Parent: parent,
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Kind: kind,
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Readonly: ro,
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}, nil
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}
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func (o *Snapshotter) Prepare(key, parent string) ([]containerd.Mount, error) {
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active, err := o.newActiveDir(key)
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if err != nil {
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return nil, err
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@ -45,10 +110,10 @@ func (o *Driver) Prepare(key, parent string) ([]containerd.Mount, error) {
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return nil, err
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}
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}
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return o.Mounts(key)
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return active.mounts(o.links)
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}
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func (o *Driver) View(key, parent string) ([]containerd.Mount, error) {
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func (o *Snapshotter) View(key, parent string) ([]containerd.Mount, error) {
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panic("not implemented")
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}
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@ -56,70 +121,69 @@ func (o *Driver) View(key, parent string) ([]containerd.Mount, error) {
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// called on an read-write or readonly transaction.
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//
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// This can be used to recover mounts after calling View or Prepare.
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func (o *Driver) Mounts(key string) ([]containerd.Mount, error) {
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func (o *Snapshotter) Mounts(key string) ([]containerd.Mount, error) {
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active := o.getActive(key)
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return active.mounts(o.cache)
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return active.mounts(o.links)
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}
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func (o *Driver) Commit(name, key string) error {
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func (o *Snapshotter) Commit(name, key string) error {
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active := o.getActive(key)
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return active.commit(name, o.cache)
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return active.commit(name, o.links)
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}
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// Remove abandons the transaction identified by key. All resources
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// associated with the key will be removed.
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func (o *Driver) Remove(key string) error {
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panic("not implemented")
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}
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// Parent returns the parent of snapshot identified by name.
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func (o *Driver) Parent(name string) (string, error) {
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ppath, err := o.cache.get(filepath.Join(o.root, "snapshots", hash(name)))
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if err != nil {
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if os.IsNotExist(err) {
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return "", nil // no parent
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}
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return "", err
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}
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p, err := ioutil.ReadFile(filepath.Join(ppath, "name"))
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if err != nil {
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return "", err
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}
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return string(p), nil
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}
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// Exists returns true if the snapshot with name exists.
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func (o *Driver) Exists(name string) bool {
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panic("not implemented")
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}
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// Delete the snapshot idenfitied by name.
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//
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// If name has children, the operation will fail.
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func (o *Driver) Delete(name string) error {
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func (o *Snapshotter) Remove(key string) error {
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panic("not implemented")
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}
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// Walk the committed snapshots.
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func (o *Driver) Walk(fn func(name string) error) error {
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panic("not implemented")
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func (o *Snapshotter) Walk(fn func(snapshot.Info) error) error {
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root := filepath.Join(o.root, "index")
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return filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
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if err != nil {
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return err
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}
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if path == root {
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return nil
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}
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if fi.Mode()&os.ModeSymlink == 0 {
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// only follow links
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return filepath.SkipDir
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}
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target, err := o.links.get(path)
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if err != nil {
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if !os.IsNotExist(err) {
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return err
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}
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}
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si, err := o.stat(target)
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if err != nil {
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return err
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}
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if err := fn(si); err != nil {
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return err
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}
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return nil
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})
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}
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// Active will call fn for each active transaction.
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func (o *Driver) Active(fn func(key string) error) error {
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panic("not implemented")
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}
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func (o *Driver) newActiveDir(key string) (*activeDir, error) {
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func (o *Snapshotter) newActiveDir(key string) (*activeDir, error) {
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var (
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path = filepath.Join(o.root, "active", hash(key))
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path = filepath.Join(o.root, "active", hash(key))
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name = filepath.Join(path, "name")
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indexlink = filepath.Join(o.root, "index", hash(key))
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)
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a := &activeDir{
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path: path,
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snapshotsDir: filepath.Join(o.root, "snapshots"),
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committedDir: filepath.Join(o.root, "committed"),
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indexlink: indexlink,
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}
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for _, p := range []string{
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"work",
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@ -130,13 +194,26 @@ func (o *Driver) newActiveDir(key string) (*activeDir, error) {
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return nil, err
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}
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}
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if err := ioutil.WriteFile(name, []byte(key), 0644); err != nil {
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a.delete()
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return nil, err
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}
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// link from namespace
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if err := os.Symlink(path, indexlink); err != nil {
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a.delete()
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return nil, err
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}
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return a, nil
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}
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func (o *Driver) getActive(key string) *activeDir {
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func (o *Snapshotter) getActive(key string) *activeDir {
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return &activeDir{
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path: filepath.Join(o.root, "active", hash(key)),
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snapshotsDir: filepath.Join(o.root, "snapshots"),
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committedDir: filepath.Join(o.root, "committed"),
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indexlink: filepath.Join(o.root, "index", hash(key)),
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}
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}
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@ -145,8 +222,9 @@ func hash(k string) string {
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}
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type activeDir struct {
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snapshotsDir string
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committedDir string
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path string
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indexlink string
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}
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func (a *activeDir) delete() error {
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@ -154,7 +232,7 @@ func (a *activeDir) delete() error {
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}
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func (a *activeDir) setParent(name string) error {
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return os.Symlink(filepath.Join(a.snapshotsDir, hash(name)), filepath.Join(a.path, "parent"))
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return os.Symlink(filepath.Join(a.committedDir, hash(name)), filepath.Join(a.path, "parent"))
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}
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func (a *activeDir) commit(name string, c *cache) error {
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@ -173,7 +251,20 @@ func (a *activeDir) commit(name string, c *cache) error {
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}
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c.invalidate(a.path) // clears parent cache, since we end up moving.
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return os.Rename(a.path, filepath.Join(a.snapshotsDir, hash(name)))
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c.invalidate(filepath.Join(a.path, "parent"))
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c.invalidate(a.indexlink)
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committed := filepath.Join(a.committedDir, hash(name))
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if err := os.Rename(a.path, committed); err != nil {
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return err
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}
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if err := os.Remove(a.indexlink); err != nil {
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return err
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}
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indexlink := filepath.Join(filepath.Dir(a.indexlink), hash(name))
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return os.Symlink(committed, indexlink)
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}
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func (a *activeDir) mounts(c *cache) ([]containerd.Mount, error) {
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@ -183,10 +274,11 @@ func (a *activeDir) mounts(c *cache) ([]containerd.Mount, error) {
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current = a.path
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)
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for {
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if current, err = c.get(current); err != nil {
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if current, err = c.get(filepath.Join(current, "parent")); err != nil {
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if os.IsNotExist(err) {
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break
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}
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return nil, err
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}
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parents = append(parents, filepath.Join(current, "fs"))
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@ -221,32 +313,32 @@ func (a *activeDir) mounts(c *cache) ([]containerd.Mount, error) {
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func newCache() *cache {
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return &cache{
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parents: make(map[string]string),
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links: make(map[string]string),
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}
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}
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type cache struct {
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mu sync.Mutex
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parents map[string]string
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mu sync.Mutex
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links map[string]string
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}
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func (c *cache) get(path string) (string, error) {
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c.mu.Lock()
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defer c.mu.Unlock()
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parentRoot, ok := c.parents[path]
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target, ok := c.links[path]
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if !ok {
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link, err := os.Readlink(filepath.Join(path, "parent"))
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link, err := os.Readlink(path)
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if err != nil {
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return "", err
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}
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c.parents[path], parentRoot = link, link
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c.links[path], target = link, link
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}
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return parentRoot, nil
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return target, nil
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}
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func (c *cache) invalidate(path string) {
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c.mu.Lock()
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defer c.mu.Unlock()
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delete(c.parents, path)
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delete(c.links, path)
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}
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@ -13,12 +13,24 @@ import (
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)
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func TestOverlay(t *testing.T) {
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testutil.RequiresRoot(t)
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snapshot.SnapshotterSuite(t, "Overlay", func(root string) (snapshot.Snapshotter, func(), error) {
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snapshotter, err := NewSnapshotter(root)
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if err != nil {
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t.Fatal(err)
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}
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return snapshotter, func() {}, nil
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})
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}
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func TestOverlayMounts(t *testing.T) {
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root, err := ioutil.TempDir("", "overlay")
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if err != nil {
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t.Fatal(err)
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}
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defer os.RemoveAll(root)
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o, err := NewDriver(root)
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o, err := NewSnapshotter(root)
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if err != nil {
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t.Error(err)
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return
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@ -53,7 +65,7 @@ func TestOverlayCommit(t *testing.T) {
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t.Fatal(err)
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}
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defer os.RemoveAll(root)
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o, err := NewDriver(root)
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o, err := NewSnapshotter(root)
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if err != nil {
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t.Error(err)
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return
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@ -81,7 +93,7 @@ func TestOverlayOverlayMount(t *testing.T) {
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t.Fatal(err)
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}
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defer os.RemoveAll(root)
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o, err := NewDriver(root)
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o, err := NewSnapshotter(root)
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if err != nil {
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t.Error(err)
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return
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@ -115,7 +127,7 @@ func TestOverlayOverlayMount(t *testing.T) {
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sh = hash("base")
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work = "workdir=" + filepath.Join(root, "active", ah, "work")
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upper = "upperdir=" + filepath.Join(root, "active", ah, "fs")
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lower = "lowerdir=" + filepath.Join(root, "snapshots", sh, "fs")
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lower = "lowerdir=" + filepath.Join(root, "committed", sh, "fs")
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)
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for i, v := range []string{
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work,
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@ -135,7 +147,7 @@ func TestOverlayOverlayRead(t *testing.T) {
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t.Fatal(err)
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}
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defer os.RemoveAll(root)
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o, err := NewDriver(root)
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o, err := NewSnapshotter(root)
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if err != nil {
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t.Error(err)
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return
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@ -179,15 +191,3 @@ func TestOverlayOverlayRead(t *testing.T) {
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return
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}
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}
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func TestOverlayDriverSuite(t *testing.T) {
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testutil.RequiresRoot(t)
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snapshot.DriverSuite(t, "Overlay", func(root string) (snapshot.Driver, func(), error) {
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driver, err := NewDriver(root)
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if err != nil {
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t.Fatal(err)
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}
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return driver, func() {}, nil
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})
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}
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