Merge pull request #26342 from cpuguy83/20079_restore_volume_migrate

restore migrating pre-1.7.0 volumes

daemon/volumes_unix.go

@@ -3,12 +3,18 @@
 package daemon
 
 import (
+	"encoding/json"
 	"os"
+	"path/filepath"
 	"sort"
 	"strconv"
+	"strings"
 
 	"github.com/docker/docker/container"
 	"github.com/docker/docker/volume"
+	"github.com/docker/docker/volume/drivers"
+	"github.com/docker/docker/volume/local"
+	"github.com/pkg/errors"
 )
 
 // setupMounts iterates through each of the mount points for a container and
@@ -85,3 +91,74 @@ func setBindModeIfNull(bind *volume.MountPoint) *volume.MountPoint {
 	}
 	return bind
 }
+
+// migrateVolume links the contents of a volume created pre Docker 1.7
+// into the location expected by the local driver.
+// It creates a symlink from DOCKER_ROOT/vfs/dir/VOLUME_ID to DOCKER_ROOT/volumes/VOLUME_ID/_container_data.
+// It preserves the volume json configuration generated pre Docker 1.7 to be able to
+// downgrade from Docker 1.7 to Docker 1.6 without losing volume compatibility.
+func migrateVolume(id, vfs string) error {
+	l, err := volumedrivers.GetDriver(volume.DefaultDriverName)
+	if err != nil {
+		return err
+	}
+
+	newDataPath := l.(*local.Root).DataPath(id)
+	fi, err := os.Stat(newDataPath)
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+
+	if fi != nil && fi.IsDir() {
+		return nil
+	}
+
+	return os.Symlink(vfs, newDataPath)
+}
+
+// verifyVolumesInfo ports volumes configured for the containers pre docker 1.7.
+// It reads the container configuration and creates valid mount points for the old volumes.
+func (daemon *Daemon) verifyVolumesInfo(container *container.Container) error {
+	// Inspect old structures only when we're upgrading from old versions
+	// to versions >= 1.7 and the MountPoints has not been populated with volumes data.
+	type volumes struct {
+		Volumes   map[string]string
+		VolumesRW map[string]bool
+	}
+	cfgPath, err := container.ConfigPath()
+	if err != nil {
+		return err
+	}
+	f, err := os.Open(cfgPath)
+	if err != nil {
+		return errors.Wrap(err, "could not open container config")
+	}
+	var cv volumes
+	if err := json.NewDecoder(f).Decode(&cv); err != nil {
+		return errors.Wrap(err, "could not decode container config")
+	}
+
+	if len(container.MountPoints) == 0 && len(cv.Volumes) > 0 {
+		for destination, hostPath := range cv.Volumes {
+			vfsPath := filepath.Join(daemon.root, "vfs", "dir")
+			rw := cv.VolumesRW != nil && cv.VolumesRW[destination]
+
+			if strings.HasPrefix(hostPath, vfsPath) {
+				id := filepath.Base(hostPath)
+				v, err := daemon.volumes.CreateWithRef(id, volume.DefaultDriverName, container.ID, nil, nil)
+				if err != nil {
+					return err
+				}
+				if err := migrateVolume(id, hostPath); err != nil {
+					return err
+				}
+				container.AddMountPointWithVolume(destination, v, true)
+			} else { // Bind mount
+				m := volume.MountPoint{Source: hostPath, Destination: destination, RW: rw}
+				container.MountPoints[destination] = &m
+			}
+		}
+		return container.ToDisk()
+	}
+	return nil
+}