github.com/uriddle/docker@v0.0.0-20210926094723-4072e6aeb013/daemon/volumes_unix.go

// +build !windows

package daemon

import (
	"os"
	"sort"
	"strconv"

	"github.com/docker/docker/container"
	"github.com/docker/docker/daemon/execdriver"
	"github.com/docker/docker/volume"
	volumedrivers "github.com/docker/docker/volume/drivers"
	"github.com/docker/docker/volume/local"
)

// setupMounts iterates through each of the mount points for a container and
// calls Setup() on each. It also looks to see if is a network mount such as
// /etc/resolv.conf, and if it is not, appends it to the array of mounts.
func (daemon *Daemon) setupMounts(container *container.Container) ([]execdriver.Mount, error) {
	var mounts []execdriver.Mount
	for _, m := range container.MountPoints {
		if err := daemon.lazyInitializeVolume(container.ID, m); err != nil {
			return nil, err
		}
		path, err := m.Setup()
		if err != nil {
			return nil, err
		}
		if !container.TrySetNetworkMount(m.Destination, path) {
			mnt := execdriver.Mount{
				Source:      path,
				Destination: m.Destination,
				Writable:    m.RW,
				Propagation: m.Propagation,
			}
			if m.Volume != nil {
				attributes := map[string]string{
					"driver":      m.Volume.DriverName(),
					"container":   container.ID,
					"destination": m.Destination,
					"read/write":  strconv.FormatBool(m.RW),
					"propagation": m.Propagation,
				}
				daemon.LogVolumeEvent(m.Volume.Name(), "mount", attributes)
			}
			mounts = append(mounts, mnt)
		}
	}

	mounts = sortMounts(mounts)
	netMounts := container.NetworkMounts()
	// if we are going to mount any of the network files from container
	// metadata, the ownership must be set properly for potential container
	// remapped root (user namespaces)
	rootUID, rootGID := daemon.GetRemappedUIDGID()
	for _, mount := range netMounts {
		if err := os.Chown(mount.Source, rootUID, rootGID); err != nil {
			return nil, err
		}
	}
	return append(mounts, netMounts...), nil
}

// sortMounts sorts an array of mounts in lexicographic order. This ensure that
// when mounting, the mounts don't shadow other mounts. For example, if mounting
// /etc and /etc/resolv.conf, /etc/resolv.conf must not be mounted first.
func sortMounts(m []execdriver.Mount) []execdriver.Mount {
	sort.Sort(mounts(m))
	return m
}

// 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.Lookup(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)
}

// validVolumeLayout checks whether the volume directory layout
// is valid to work with Docker post 1.7 or not.
func validVolumeLayout(files []os.FileInfo) bool {
	if len(files) == 1 && files[0].Name() == local.VolumeDataPathName && files[0].IsDir() {
		return true
	}

	if len(files) != 2 {
		return false
	}

	for _, f := range files {
		if f.Name() == "config.json" ||
			(f.Name() == local.VolumeDataPathName && f.Mode()&os.ModeSymlink == os.ModeSymlink) {
			// Old volume configuration, we ignore it
			continue
		}
		return false
	}

	return true
}

// setBindModeIfNull is platform specific processing to ensure the
// shared mode is set to 'z' if it is null. This is called in the case
// of processing a named volume and not a typical bind.
func setBindModeIfNull(bind *volume.MountPoint) *volume.MountPoint {
	if bind.Mode == "" {
		bind.Mode = "z"
	}
	return bind
}