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package snapshot
import (
"context"
"os"
"strings"
"sync"
"github.com/containerd/containerd/mount"
"github.com/containerd/containerd/pkg/userns"
"github.com/containerd/containerd/snapshots"
"github.com/docker/docker/pkg/idtools"
"github.com/moby/buildkit/executor"
"github.com/pkg/errors"
)
type Mountable = executor.MountableRef
// Snapshotter defines interface that any snapshot implementation should satisfy
type Snapshotter interface {
Name() string
Mounts(ctx context.Context, key string) (Mountable, error)
Prepare(ctx context.Context, key, parent string, opts ...snapshots.Opt) error
View(ctx context.Context, key, parent string, opts ...snapshots.Opt) (Mountable, error)
Stat(ctx context.Context, key string) (snapshots.Info, error)
Update(ctx context.Context, info snapshots.Info, fieldpaths ...string) (snapshots.Info, error)
Usage(ctx context.Context, key string) (snapshots.Usage, error)
Commit(ctx context.Context, name, key string, opts ...snapshots.Opt) error
Remove(ctx context.Context, key string) error
Walk(ctx context.Context, fn snapshots.WalkFunc, filters ...string) error
Close() error
IdentityMapping() *idtools.IdentityMapping
}
func FromContainerdSnapshotter(name string, s snapshots.Snapshotter, idmap *idtools.IdentityMapping) Snapshotter {
return &fromContainerd{name: name, Snapshotter: s, idmap: idmap}
}
type fromContainerd struct {
name string
snapshots.Snapshotter
idmap *idtools.IdentityMapping
}
func (s *fromContainerd) Name() string {
return s.name
}
func (s *fromContainerd) Mounts(ctx context.Context, key string) (Mountable, error) {
mounts, err := s.Snapshotter.Mounts(ctx, key)
if err != nil {
return nil, err
}
return &staticMountable{mounts: mounts, idmap: s.idmap, id: key}, nil
}
func (s *fromContainerd) Prepare(ctx context.Context, key, parent string, opts ...snapshots.Opt) error {
_, err := s.Snapshotter.Prepare(ctx, key, parent, opts...)
return err
}
func (s *fromContainerd) View(ctx context.Context, key, parent string, opts ...snapshots.Opt) (Mountable, error) {
mounts, err := s.Snapshotter.View(ctx, key, parent, opts...)
if err != nil {
return nil, err
}
return &staticMountable{mounts: mounts, idmap: s.idmap, id: key}, nil
}
func (s *fromContainerd) IdentityMapping() *idtools.IdentityMapping {
return s.idmap
}
func (s *fromContainerd) Commit(ctx context.Context, name, key string, opts ...snapshots.Opt) error {
info, err := s.Stat(ctx, key)
if err != nil {
return errors.Wrap(err, "failed to stat active key during commit")
}
opts = append(opts, snapshots.WithLabels(snapshots.FilterInheritedLabels(info.Labels)))
return s.Snapshotter.Commit(ctx, name, key, opts...)
}
// NewContainerdSnapshotter converts snapshotter to containerd snapshotter
func NewContainerdSnapshotter(s Snapshotter) (snapshots.Snapshotter, func() error) {
cs := &containerdSnapshotter{Snapshotter: s}
return cs, cs.release
}
type containerdSnapshotter struct {
mu sync.Mutex
releasers []func() error
Snapshotter
}
func (cs *containerdSnapshotter) release() error {
cs.mu.Lock()
defer cs.mu.Unlock()
var err error
for _, f := range cs.releasers {
if err1 := f(); err1 != nil && err == nil {
err = err1
}
}
return err
}
func (cs *containerdSnapshotter) returnMounts(mf Mountable) ([]mount.Mount, error) {
mounts, release, err := mf.Mount()
if err != nil {
return nil, err
}
cs.mu.Lock()
cs.releasers = append(cs.releasers, release)
cs.mu.Unlock()
redirectDirOption := getRedirectDirOption()
if redirectDirOption != "" {
mounts = setRedirectDir(mounts, redirectDirOption)
}
return mounts, nil
}
func (cs *containerdSnapshotter) Mounts(ctx context.Context, key string) ([]mount.Mount, error) {
mf, err := cs.Snapshotter.Mounts(ctx, key)
if err != nil {
return nil, err
}
return cs.returnMounts(mf)
}
func (cs *containerdSnapshotter) Prepare(ctx context.Context, key, parent string, opts ...snapshots.Opt) ([]mount.Mount, error) {
if err := cs.Snapshotter.Prepare(ctx, key, parent, opts...); err != nil {
return nil, err
}
return cs.Mounts(ctx, key)
}
func (cs *containerdSnapshotter) View(ctx context.Context, key, parent string, opts ...snapshots.Opt) ([]mount.Mount, error) {
mf, err := cs.Snapshotter.View(ctx, key, parent, opts...)
if err != nil {
return nil, err
}
return cs.returnMounts(mf)
}
var redirectDirOption string
var redirectDirOptionOnce sync.Once
func getRedirectDirOption() string {
redirectDirOptionOnce.Do(func() {
if _, err := os.Stat("/sys/module/overlay/parameters/redirect_dir"); err != nil {
redirectDirOption = "" // redirect_dir unsupported
return
}
if userns.RunningInUserNS() {
// userxattr (kernel >= 5.11) disables redirect_dir and doesn't allow specifying "off".
redirectDirOption = ""
return
}
redirectDirOption = "off" // disable redirect_dir to avoid broken diff
})
return redirectDirOption
}
func setRedirectDir(mounts []mount.Mount, redirectDirOption string) (ret []mount.Mount) {
if redirectDirOption == "" {
return mounts
}
for _, m := range mounts {
// Replace redirect_dir options, but only for overlay.
// redirect_dir is not supported by fuse-overlayfs.
if m.Type == "overlay" {
var opts []string
for _, o := range m.Options {
if strings.HasPrefix(o, "redirect_dir=") {
continue
}
opts = append(opts, o)
}
m.Options = append(opts, "redirect_dir="+redirectDirOption)
}
ret = append(ret, m)
}
return ret
}
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