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snapshotter.go
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snapshotter.go
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package snapshot
import (
"context"
"os"
"sync"
"sync/atomic"
"github.com/containerd/containerd/mount"
"github.com/containerd/containerd/snapshots"
"github.com/docker/docker/pkg/idtools"
)
type Mountable interface {
// ID() string
Mount() ([]mount.Mount, func() error, error)
IdentityMapping() *idtools.IdentityMapping
}
// 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
}
type staticMountable struct {
count int32
id string
mounts []mount.Mount
idmap *idtools.IdentityMapping
}
func (cm *staticMountable) Mount() ([]mount.Mount, func() error, error) {
atomic.AddInt32(&cm.count, 1)
return cm.mounts, func() error {
if atomic.AddInt32(&cm.count, -1) < 0 {
if v := os.Getenv("BUILDKIT_DEBUG_PANIC_ON_ERROR"); v == "1" {
panic("release of released mount " + cm.id)
}
}
return nil
}, nil
}
func (cm *staticMountable) IdentityMapping() *idtools.IdentityMapping {
return cm.idmap
}
// 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()
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)
}