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snapshot/overlay: implement view

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Allow creating actives without an upper directory for
capturing changes. Actives without the upper directory
will always be mounted read only. Read only actives
must have a parent.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
This commit is contained in:
Derek McGowan 2017-02-17 16:34:21 -08:00
parent 5bdfeead5e
commit ca56448263
2 changed files with 83 additions and 13 deletions
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49
snapshot/overlay/overlay.go
View file

@ -102,7 +102,7 @@ func (o *Snapshotter) stat(path string) (snapshot.Info, error) {
}
func (o *Snapshotter) Prepare(ctx context.Context, key, parent string) ([]containerd.Mount, error) {
active, err := o.newActiveDir(key)
active, err := o.newActiveDir(key, false)
if err != nil {
return nil, err
}
@ -115,7 +115,16 @@ func (o *Snapshotter) Prepare(ctx context.Context, key, parent string) ([]contai
}
func (o *Snapshotter) View(ctx context.Context, key, parent string) ([]containerd.Mount, error) {
panic("not implemented")
active, err := o.newActiveDir(key, true)
if err != nil {
return nil, err
}
if parent != "" {
if err := active.setParent(parent); err != nil {
return nil, err
}
}
return active.mounts(o.links)
}
// Mounts returns the mounts for the transaction identified by key. Can be
@ -175,7 +184,7 @@ func (o *Snapshotter) Walk(ctx context.Context, fn func(context.Context, snapsho
})
}
func (o *Snapshotter) newActiveDir(key string) (*activeDir, error) {
func (o *Snapshotter) newActiveDir(key string, readonly bool) (*activeDir, error) {
var (
path = filepath.Join(o.root, "active", hash(key))
name = filepath.Join(path, "name")
@ -186,11 +195,18 @@ func (o *Snapshotter) newActiveDir(key string) (*activeDir, error) {
committedDir: filepath.Join(o.root, "committed"),
indexlink: indexlink,
}
for _, p := range []string{
"work",
"fs",
} {
if err := os.MkdirAll(filepath.Join(path, p), 0700); err != nil {
if !readonly {
for _, p := range []string{
"work",
"fs",
} {
if err := os.MkdirAll(filepath.Join(path, p), 0700); err != nil {
a.delete()
return nil, err
}
}
} else {
if err := os.MkdirAll(path, 0700); err != nil {
a.delete()
return nil, err
}
@ -286,7 +302,7 @@ func (a *activeDir) mounts(c *cache) ([]containerd.Mount, error) {
}
if len(parents) == 0 {
// if we only have one layer/no parents then just return a bind mount as overlay
// will not work
// will not work, readonly always has parent
return []containerd.Mount{
{
Source: filepath.Join(a.path, "fs"),
@ -298,11 +314,18 @@ func (a *activeDir) mounts(c *cache) ([]containerd.Mount, error) {
},
}, nil
}
options := []string{
fmt.Sprintf("workdir=%s", filepath.Join(a.path, "work")),
fmt.Sprintf("upperdir=%s", filepath.Join(a.path, "fs")),
fmt.Sprintf("lowerdir=%s", strings.Join(parents, ":")),
var options []string
if _, err := os.Stat(filepath.Join(a.path, "fs")); err == nil {
options = append(options,
fmt.Sprintf("workdir=%s", filepath.Join(a.path, "work")),
fmt.Sprintf("upperdir=%s", filepath.Join(a.path, "fs")),
)
} else if !os.IsNotExist(err) {
return nil, err
}
options = append(options, fmt.Sprintf("lowerdir=%s", strings.Join(parents, ":")))
return []containerd.Mount{
{
Type: "overlay",