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package snapshotter
import (
"context"
"os"
"path/filepath"
"github.com/containerd/containerd/mount"
"github.com/containerd/log"
"github.com/docker/docker/daemon/graphdriver"
"github.com/docker/docker/pkg/idtools"
"github.com/moby/locker"
"github.com/moby/sys/mountinfo"
)
// Mounter handles mounting/unmounting things coming in from a snapshotter
// with optional reference counting if needed by the filesystem
type Mounter interface {
// Mount mounts the rootfs for a container and returns the mount point
Mount(mounts []mount.Mount, containerID string) (string, error)
// Unmount unmounts the container rootfs
Unmount(target string) error
// Mounted returns a target mountpoint if it's already mounted
Mounted(containerID string) (string, error)
}
// NewMounter creates a new mounter for the provided snapshotter
func NewMounter(home string, snapshotter string, idMap idtools.IdentityMapping) *refCountMounter {
return &refCountMounter{
base: mounter{
home: home,
snapshotter: snapshotter,
idMap: idMap,
},
rc: graphdriver.NewRefCounter(checker()),
locker: locker.New(),
}
}
type refCountMounter struct {
rc *graphdriver.RefCounter
locker *locker.Locker
base mounter
}
func (m *refCountMounter) Mount(mounts []mount.Mount, containerID string) (target string, retErr error) {
target = m.base.target(containerID)
_, err := os.Stat(target)
if err != nil && !os.IsNotExist(err) {
return "", err
}
if count := m.rc.Increment(target); count > 1 {
return target, nil
}
m.locker.Lock(target)
defer m.locker.Unlock(target)
defer func() {
if retErr != nil {
if c := m.rc.Decrement(target); c <= 0 {
if mntErr := unmount(target); mntErr != nil {
log.G(context.TODO()).Errorf("error unmounting %s: %v", target, mntErr)
}
if rmErr := os.Remove(target); rmErr != nil && !os.IsNotExist(rmErr) {
log.G(context.TODO()).Debugf("Failed to remove %s: %v: %v", target, rmErr, err)
}
}
}
}()
return m.base.Mount(mounts, containerID)
}
func (m *refCountMounter) Unmount(target string) error {
if count := m.rc.Decrement(target); count > 0 {
return nil
}
m.locker.Lock(target)
defer m.locker.Unlock(target)
if err := unmount(target); err != nil {
log.G(context.TODO()).Debugf("Failed to unmount %s: %v", target, err)
}
if err := os.Remove(target); err != nil {
log.G(context.TODO()).WithError(err).WithField("dir", target).Error("failed to remove mount temp dir")
}
return nil
}
func (m *refCountMounter) Mounted(containerID string) (string, error) {
mounted, err := m.base.Mounted(containerID)
if err != nil || mounted == "" {
return mounted, err
}
target := m.base.target(containerID)
// Check if the refcount is non-zero.
m.rc.Increment(target)
if m.rc.Decrement(target) > 0 {
return mounted, nil
}
return "", nil
}
type mounter struct {
home string
snapshotter string
idMap idtools.IdentityMapping
}
func (m mounter) Mount(mounts []mount.Mount, containerID string) (string, error) {
target := m.target(containerID)
root := m.idMap.RootPair()
if err := idtools.MkdirAllAndChown(filepath.Dir(target), 0o710, idtools.Identity{
UID: idtools.CurrentIdentity().UID,
GID: root.GID,
}); err != nil {
return "", err
}
if err := idtools.MkdirAllAndChown(target, 0o710, root); err != nil {
return "", err
}
return target, mount.All(mounts, target)
}
func (m mounter) Unmount(target string) error {
return unmount(target)
}
func (m mounter) Mounted(containerID string) (string, error) {
target := m.target(containerID)
mounted, err := mountinfo.Mounted(target)
if err != nil || !mounted {
return "", err
}
return target, nil
}
func (m mounter) target(containerID string) string {
return filepath.Join(m.home, "rootfs", m.snapshotter, containerID)
}
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