snapshot/btrfs: update btrfs to snappshotter
Updates the btrfs snapshotter to meet the interface and current tests. Mostly, we merge the keyspace into a common index. Like with the overlay driver, we will still need to do more verification work to ensure idempotence of key collisions. Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day
parent
e6c1bb0ff2
commit
9c4b235954
2 changed files with 177 additions and 102 deletions
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@ -6,47 +6,33 @@ import (
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"io/ioutil"
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"os"
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"path/filepath"
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"strings"
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"github.com/docker/containerd"
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"github.com/docker/containerd/log"
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"github.com/docker/containerd/snapshot"
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"github.com/pkg/errors"
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"github.com/stevvooe/go-btrfs"
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)
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type Driver struct {
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type Snapshotter struct {
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device string // maybe we can resolve it with path?
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root string // root provides paths for internal storage.
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}
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func NewDriver(device, root string) (*Driver, error) {
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return &Driver{device: device, root: root}, nil
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}
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func (b *Driver) Prepare(key, parent string) ([]containerd.Mount, error) {
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return b.makeActive(key, parent, false)
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}
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func (b *Driver) View(key, parent string) ([]containerd.Mount, error) {
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return b.makeActive(key, parent, true)
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}
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func (b *Driver) makeActive(key, parent string, readonly bool) ([]containerd.Mount, error) {
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func NewSnapshotter(device, root string) (*Snapshotter, error) {
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var (
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active = filepath.Join(b.root, "active")
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parents = filepath.Join(b.root, "parents")
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snapshots = filepath.Join(b.root, "snapshots")
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names = filepath.Join(b.root, "names")
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keyh = hash(key)
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parenth = hash(parent)
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dir = filepath.Join(active, keyh)
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namep = filepath.Join(names, keyh)
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parentlink = filepath.Join(parents, keyh)
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parentp = filepath.Join(snapshots, parenth)
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active = filepath.Join(root, "active")
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snapshots = filepath.Join(root, "snapshots")
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parents = filepath.Join(root, "parents")
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index = filepath.Join(root, "index")
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names = filepath.Join(root, "names")
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)
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for _, path := range []string{
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active,
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snapshots,
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parents,
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index,
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names,
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} {
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if err := os.MkdirAll(path, 0755); err != nil {
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@ -54,15 +40,118 @@ func (b *Driver) makeActive(key, parent string, readonly bool) ([]containerd.Mou
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}
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}
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return &Snapshotter{device: device, root: root}, nil
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}
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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 (b *Snapshotter) Stat(key string) (snapshot.Info, error) {
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// resolve the snapshot out of the index.
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target, err := os.Readlink(filepath.Join(b.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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return b.stat(target)
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}
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func (b *Snapshotter) stat(target string) (snapshot.Info, error) {
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var (
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parents = filepath.Join(b.root, "parents")
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names = filepath.Join(b.root, "names")
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namep = filepath.Join(names, filepath.Base(target))
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parentlink = filepath.Join(parents, filepath.Base(target))
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)
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// grab information about the subvolume
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info, err := btrfs.SubvolInfo(target)
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if err != nil {
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return snapshot.Info{}, err
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}
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// read the name out of the names!
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nameraw, err := ioutil.ReadFile(namep)
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if err != nil {
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return snapshot.Info{}, err
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}
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// resolve the parents path.
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parentp, err := os.Readlink(parentlink)
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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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var parent string
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if parentp != "" {
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// okay, grab the basename of the parent and look up its name!
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parentnamep := filepath.Join(names, filepath.Base(parentp))
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p, err := ioutil.ReadFile(parentnamep)
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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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kind := snapshot.KindCommitted
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if strings.HasPrefix(target, filepath.Join(b.root, "active")) {
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kind = snapshot.KindActive
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}
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return snapshot.Info{
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Name: string(nameraw),
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Parent: parent,
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Readonly: info.Readonly,
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Kind: kind,
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}, nil
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}
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func (b *Snapshotter) Prepare(key, parent string) ([]containerd.Mount, error) {
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return b.makeActive(key, parent, false)
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}
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func (b *Snapshotter) View(key, parent string) ([]containerd.Mount, error) {
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return b.makeActive(key, parent, true)
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}
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func (b *Snapshotter) makeActive(key, parent string, readonly bool) ([]containerd.Mount, error) {
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var (
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active = filepath.Join(b.root, "active")
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snapshots = filepath.Join(b.root, "snapshots")
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parents = filepath.Join(b.root, "parents")
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index = filepath.Join(b.root, "index")
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names = filepath.Join(b.root, "names")
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keyh = hash(key)
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parenth = hash(parent)
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target = filepath.Join(active, keyh)
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namep = filepath.Join(names, keyh)
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indexlink = filepath.Join(index, keyh)
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parentlink = filepath.Join(parents, keyh)
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parentp = filepath.Join(snapshots, parenth) // parent must be restricted to snaps
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)
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if parent == "" {
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// create new subvolume
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// btrfs subvolume create /dir
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if err := btrfs.SubvolCreate(dir); err != nil {
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if err := btrfs.SubvolCreate(target); err != nil {
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return nil, err
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}
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} else {
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// btrfs subvolume snapshot /parent /subvol
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if err := btrfs.SubvolSnapshot(dir, parentp, readonly); err != nil {
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if err := btrfs.SubvolSnapshot(target, parentp, readonly); err != nil {
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return nil, err
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}
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@ -71,14 +160,19 @@ func (b *Driver) makeActive(key, parent string, readonly bool) ([]containerd.Mou
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}
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}
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// write in the name
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if err := ioutil.WriteFile(namep, []byte(key), 0644); err != nil {
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return nil, err
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}
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return b.mounts(dir)
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if err := os.Symlink(target, indexlink); err != nil {
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return nil, err
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}
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return b.mounts(target)
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}
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func (b *Driver) mounts(dir string) ([]containerd.Mount, error) {
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func (b *Snapshotter) mounts(dir string) ([]containerd.Mount, error) {
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var options []string
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// get the subvolume id back out for the mount
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@ -104,12 +198,13 @@ func (b *Driver) mounts(dir string) ([]containerd.Mount, error) {
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}, nil
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}
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func (b *Driver) Commit(name, key string) error {
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func (b *Snapshotter) Commit(name, key string) error {
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var (
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active = filepath.Join(b.root, "active")
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snapshots = filepath.Join(b.root, "snapshots")
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names = filepath.Join(b.root, "names")
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index = filepath.Join(b.root, "index")
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parents = filepath.Join(b.root, "parents")
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names = filepath.Join(b.root, "names")
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keyh = hash(key)
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nameh = hash(name)
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dir = filepath.Join(active, keyh)
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@ -118,6 +213,8 @@ func (b *Driver) Commit(name, key string) error {
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namep = filepath.Join(names, nameh)
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keyparentlink = filepath.Join(parents, keyh)
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parentlink = filepath.Join(parents, nameh)
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keyindexlink = filepath.Join(index, keyh)
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indexlink = filepath.Join(index, nameh)
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)
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info, err := btrfs.SubvolInfo(dir)
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@ -143,9 +240,7 @@ func (b *Driver) Commit(name, key string) error {
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return err
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}
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fmt.Println("commit snapshot", target)
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if err := btrfs.SubvolSnapshot(target, dir, true); err != nil {
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fmt.Println("snapshot error")
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return err
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}
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@ -154,6 +249,10 @@ func (b *Driver) Commit(name, key string) error {
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return err
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}
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if err := os.Remove(keyindexlink); err != nil {
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return err
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}
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if err := ioutil.WriteFile(namep, []byte(name), 0755); err != nil {
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return err
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}
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@ -169,6 +268,10 @@ func (b *Driver) Commit(name, key string) error {
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// into common storage, so let's not fret over it for now.
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}
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if err := os.Symlink(target, indexlink); err != nil {
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return err
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}
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if err := btrfs.SubvolDelete(dir); err != nil {
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return errors.Wrapf(err, "delete subvol failed on %v", dir)
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}
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@ -180,82 +283,54 @@ func (b *Driver) Commit(name, key string) 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 (b *Driver) Mounts(key string) ([]containerd.Mount, error) {
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func (b *Snapshotter) Mounts(key string) ([]containerd.Mount, error) {
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dir := filepath.Join(b.root, "active", hash(key))
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return b.mounts(dir)
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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 (b *Driver) Remove(key string) error {
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func (b *Snapshotter) 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 (b *Driver) Parent(name string) (string, error) {
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var (
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parents = filepath.Join(b.root, "parents")
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names = filepath.Join(b.root, "names")
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parentlink = filepath.Join(parents, hash(name))
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)
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parentp, err := os.Readlink(parentlink)
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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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return "", nil // no parent!
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}
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// okay, grab the basename of the parent and look up its name!
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parentnamep := filepath.Join(names, filepath.Base(parentp))
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p, err := ioutil.ReadFile(parentnamep)
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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 (b *Driver) Exists(name string) bool {
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target := filepath.Join(b.root, "snapshots", hash(name))
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if _, err := os.Stat(target); err != nil {
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if !os.IsNotExist(err) {
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// TODO(stevvooe): Very rare condition when this fails horribly,
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// such as an access error. Ideally, Exists is simple, but we may
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// consider returning an error.
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log.L.WithError(err).Fatal("error encountered checking for snapshot existence")
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}
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return false
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}
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return true
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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 (b *Driver) Delete(name string) error {
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panic("not implemented")
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}
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// TODO(stevvooe): The methods below are still in flux. We'll need to work
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// out the roles of active and committed snapshots for this to become more
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// clear.
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// Walk the committed snapshots.
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func (b *Driver) Walk(fn func(name string) error) error {
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panic("not implemented")
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}
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func (b *Snapshotter) Walk(fn func(snapshot.Info) error) error {
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// TODO(stevvooe): Copy-pasted almost verbatim from overlay. Really need to
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// unify the metadata for snapshot implementations.
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root := filepath.Join(b.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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// Active will call fn for each active transaction.
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func (b *Driver) Active(fn func(key string) error) error {
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panic("not implemented")
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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 := os.Readlink(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 := b.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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func hash(k string) string {
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@ -20,14 +20,14 @@ const (
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func TestBtrfs(t *testing.T) {
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testutil.RequiresRoot(t)
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snapshot.DriverSuite(t, "Btrfs", func(root string) (snapshot.Driver, func(), error) {
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snapshot.SnapshotterSuite(t, "Btrfs", func(root string) (snapshot.Snapshotter, func(), error) {
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device := setupBtrfsLoopbackDevice(t, root)
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driver, err := NewDriver(device.deviceName, root)
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snapshotter, err := NewSnapshotter(device.deviceName, 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() {
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return snapshotter, func() {
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device.remove(t)
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}, nil
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})
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@ -53,7 +53,7 @@ func TestBtrfsMounts(t *testing.T) {
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defer os.RemoveAll(root)
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target := filepath.Join(root, "test")
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b, err := NewDriver(device.deviceName, root)
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b, err := NewSnapshotter(device.deviceName, root)
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if err != nil {
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t.Fatal(err)
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}
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Reference in a new issue