forked from docker-archive/v1.10-migrator
/
devicemapper.go
123 lines (108 loc) · 2.52 KB
/
devicemapper.go
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package main
import (
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"sync"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/daemon/graphdriver/devmapper"
"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/ioutils"
)
type mount struct {
activity int
path string
}
type devicemapper struct {
sync.Mutex
mounts map[string]*mount
root string
devices *devmapper.DeviceSet
}
func NewDevicemapperChecksums(root string) Mounter {
devices, err := devmapper.NewDeviceSet(root, false, nil, nil, nil)
if err != nil {
logrus.Errorf("Can't initialize device mapper: %q", err)
os.Exit(1)
}
return &devicemapper{root: root, devices: devices, mounts: make(map[string]*mount)}
}
func (c *devicemapper) Mount(id string) (string, func(), error) {
c.Lock()
defer c.Unlock()
mounts, ok := c.mounts[id]
if !ok {
tmpdir, err := ioutil.TempDir("", "migrate-devicemapper")
if err != nil {
return "", nil, err
}
mounts = &mount{0, tmpdir}
c.mounts[id] = mounts
}
if mounts.activity == 0 {
err := c.devices.MountDevice(id, mounts.path, "")
if err != nil {
return "", nil, fmt.Errorf("Can't create snap device: %v", err)
}
}
mounts.activity++
path := filepath.Join(mounts.path, "rootfs")
// sometimes rootfs does not exist. return empty dir then
if _, err := os.Lstat(path); err != nil {
tmpdir, err := ioutil.TempDir("", "migrate-devicemapper")
if err != nil {
return "", nil, err
}
path = tmpdir
}
return path, func() {
c.umount(id)
}, nil
}
func (c *devicemapper) umount(id string) {
c.Lock()
defer c.Unlock()
c.mounts[id].activity--
if c.mounts[id].activity == 0 {
err := c.devices.UnmountDevice(id, c.mounts[id].path)
if err != nil {
logrus.Errorf("Can't umount %s: %v", id, err)
}
os.RemoveAll(c.mounts[id].path)
delete(c.mounts, id)
}
}
func (c *devicemapper) TarStream(id, parent string) (io.ReadCloser, error) {
mainPath, releaseMain, err := c.Mount(id)
if err != nil {
return nil, err
}
if parent == "" {
tar, err := archive.Tar(mainPath, archive.Uncompressed)
if err != nil {
return nil, err
}
return ioutils.NewReadCloserWrapper(tar, func() error {
releaseMain()
return tar.Close()
}), nil
}
parentPath, releaseParent, err := c.Mount(parent)
if err != nil {
releaseMain()
return nil, err
}
tar, err := Diff(mainPath, parentPath)
if err != nil {
releaseParent()
releaseMain()
return nil, err
}
return ioutils.NewReadCloserWrapper(tar, func() error {
releaseParent()
releaseMain()
return tar.Close()
}), nil
}