func (a *Driver) aufsMount(ro []string, rw, target, mountLabel string) (err error) {
defer func() {
if err != nil {
Unmount(target)
}
}()
// Mount options are clipped to page size(4096 bytes). If there are more
// layers then these are remounted individually using append.
b := make([]byte, syscall.Getpagesize()-len(mountLabel)-54) // room for xino & mountLabel
bp := copy(b, fmt.Sprintf("br:%s=rw", rw))
firstMount := true
i := 0
for {
for ; i < len(ro); i++ {
layer := fmt.Sprintf(":%s=ro+wh", ro[i])
if firstMount {
if bp+len(layer) > len(b) {
break
}
bp += copy(b[bp:], layer)
} else {
data := label.FormatMountLabel(fmt.Sprintf("append%s", layer), mountLabel)
if err = mount("none", target, "aufs", MsRemount, data); err != nil {
return
}
}
}
if firstMount {
data := label.FormatMountLabel(fmt.Sprintf("%s,dio,xino=/dev/shm/aufs.xino", string(b[:bp])), mountLabel)
if err = mount("none", target, "aufs", 0, data); err != nil {
return
}
firstMount = false
}
if i == len(ro) {
break
}
}
return
}
// Try to mount using the aufs fast path, if this fails then
// append ro layers.
func (a *Driver) tryMount(ro []string, rw, target, mountLabel string) (err error) {
var (
rwBranch = fmt.Sprintf("%s=rw", rw)
roBranches = fmt.Sprintf("%s=ro+wh:", strings.Join(ro, "=ro+wh:"))
data = label.FormatMountLabel(fmt.Sprintf("br:%v:%v,xino=/dev/shm/aufs.xino", rwBranch, roBranches), mountLabel)
)
return mount("none", target, "aufs", 0, data)
}
func (devices *DeviceSet) MountDevice(hash, path, mountLabel string) error {
info, err := devices.lookupDevice(hash)
if err != nil {
return err
}
info.lock.Lock()
defer info.lock.Unlock()
devices.Lock()
defer devices.Unlock()
if info.mountCount > 0 {
if path != info.mountPath {
return fmt.Errorf("Trying to mount devmapper device in multple places (%s, %s)", info.mountPath, path)
}
info.mountCount++
return nil
}
if err := devices.activateDeviceIfNeeded(info); err != nil {
return fmt.Errorf("Error activating devmapper device for '%s': %s", hash, err)
}
var flags uintptr = syscall.MS_MGC_VAL
fstype, err := ProbeFsType(info.DevName())
if err != nil {
return err
}
options := ""
if fstype == "xfs" {
// XFS needs nouuid or it can't mount filesystems with the same fs
options = joinMountOptions(options, "nouuid")
}
options = joinMountOptions(options, devices.mountOptions)
options = joinMountOptions(options, label.FormatMountLabel("", mountLabel))
err = syscall.Mount(info.DevName(), path, fstype, flags, joinMountOptions("discard", options))
if err != nil && err == syscall.EINVAL {
err = syscall.Mount(info.DevName(), path, fstype, flags, options)
}
if err != nil {
return fmt.Errorf("Error mounting '%s' on '%s': %s", info.DevName(), path, err)
}
info.mountCount = 1
info.mountPath = path
return nil
}
func (d *Driver) Get(id string, mountLabel string) (string, error) {
// Protect the d.active from concurrent access
d.Lock()
defer d.Unlock()
mount := d.active[id]
if mount != nil {
mount.count++
return mount.path, nil
}
mount = &ActiveMount{count: 1}
dir := d.dir(id)
if _, err := os.Stat(dir); err != nil {
return "", err
}
// If id has a root, just return it
rootDir := path.Join(dir, "root")
if _, err := os.Stat(rootDir); err == nil {
mount.path = rootDir
d.active[id] = mount
return mount.path, nil
}
lowerId, err := ioutil.ReadFile(path.Join(dir, "lower-id"))
if err != nil {
return "", err
}
lowerDir := path.Join(d.dir(string(lowerId)), "root")
upperDir := path.Join(dir, "upper")
workDir := path.Join(dir, "work")
mergedDir := path.Join(dir, "merged")
opts := fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", lowerDir, upperDir, workDir)
if err := syscall.Mount("overlay", mergedDir, "overlay", 0, label.FormatMountLabel(opts, mountLabel)); err != nil {
return "", fmt.Errorf("error creating overlay mount to %s: %v", mergedDir, err)
}
mount.path = mergedDir
mount.mounted = true
d.active[id] = mount
return mount.path, nil
}
func (a *Driver) aufsMount(ro []string, rw, target, mountLabel string) (err error) {
defer func() {
if err != nil {
Unmount(target)
}
}()
if err = a.tryMount(ro, rw, target, mountLabel); err != nil {
if err = a.mountRw(rw, target, mountLabel); err != nil {
return
}
for _, layer := range ro {
data := label.FormatMountLabel(fmt.Sprintf("append:%s=ro+wh", layer), mountLabel)
if err = mount("none", target, "aufs", MsRemount, data); err != nil {
return
}
}
}
return
}
func (a *Driver) mountRw(rw, target, mountLabel string) error {
data := label.FormatMountLabel(fmt.Sprintf("br:%s,xino=/dev/shm/aufs.xino", rw), mountLabel)
return mount("none", target, "aufs", 0, data)
}