Merge pull request #8986 from vbatts/vbatts-pkg_devicemapper_bindings

devicemapper: split out devicemapper bindings

devicemapper/attach_loopback.go

@@ -0,0 +1,129 @@
+// +build linux
+
+package devicemapper
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+
+	log "github.com/Sirupsen/logrus"
+)
+
+func stringToLoopName(src string) [LoNameSize]uint8 {
+	var dst [LoNameSize]uint8
+	copy(dst[:], src[:])
+	return dst
+}
+
+func getNextFreeLoopbackIndex() (int, error) {
+	f, err := os.OpenFile("/dev/loop-control", os.O_RDONLY, 0644)
+	if err != nil {
+		return 0, err
+	}
+	defer f.Close()
+
+	index, err := ioctlLoopCtlGetFree(f.Fd())
+	if index < 0 {
+		index = 0
+	}
+	return index, err
+}
+
+func openNextAvailableLoopback(index int, sparseFile *os.File) (loopFile *os.File, err error) {
+	// Start looking for a free /dev/loop
+	for {
+		target := fmt.Sprintf("/dev/loop%d", index)
+		index++
+
+		fi, err := os.Stat(target)
+		if err != nil {
+			if os.IsNotExist(err) {
+				log.Errorf("There are no more loopback devices available.")
+			}
+			return nil, ErrAttachLoopbackDevice
+		}
+
+		if fi.Mode()&os.ModeDevice != os.ModeDevice {
+			log.Errorf("Loopback device %s is not a block device.", target)
+			continue
+		}
+
+		// OpenFile adds O_CLOEXEC
+		loopFile, err = os.OpenFile(target, os.O_RDWR, 0644)
+		if err != nil {
+			log.Errorf("Error opening loopback device: %s", err)
+			return nil, ErrAttachLoopbackDevice
+		}
+
+		// Try to attach to the loop file
+		if err := ioctlLoopSetFd(loopFile.Fd(), sparseFile.Fd()); err != nil {
+			loopFile.Close()
+
+			// If the error is EBUSY, then try the next loopback
+			if err != syscall.EBUSY {
+				log.Errorf("Cannot set up loopback device %s: %s", target, err)
+				return nil, ErrAttachLoopbackDevice
+			}
+
+			// Otherwise, we keep going with the loop
+			continue
+		}
+		// In case of success, we finished. Break the loop.
+		break
+	}
+
+	// This can't happen, but let's be sure
+	if loopFile == nil {
+		log.Errorf("Unreachable code reached! Error attaching %s to a loopback device.", sparseFile.Name())
+		return nil, ErrAttachLoopbackDevice
+	}
+
+	return loopFile, nil
+}
+
+// attachLoopDevice attaches the given sparse file to the next
+// available loopback device. It returns an opened *os.File.
+func AttachLoopDevice(sparseName string) (loop *os.File, err error) {
+
+	// Try to retrieve the next available loopback device via syscall.
+	// If it fails, we discard error and start loopking for a
+	// loopback from index 0.
+	startIndex, err := getNextFreeLoopbackIndex()
+	if err != nil {
+		log.Debugf("Error retrieving the next available loopback: %s", err)
+	}
+
+	// OpenFile adds O_CLOEXEC
+	sparseFile, err := os.OpenFile(sparseName, os.O_RDWR, 0644)
+	if err != nil {
+		log.Errorf("Error opening sparse file %s: %s", sparseName, err)
+		return nil, ErrAttachLoopbackDevice
+	}
+	defer sparseFile.Close()
+
+	loopFile, err := openNextAvailableLoopback(startIndex, sparseFile)
+	if err != nil {
+		return nil, err
+	}
+
+	// Set the status of the loopback device
+	loopInfo := &LoopInfo64{
+		loFileName: stringToLoopName(loopFile.Name()),
+		loOffset:   0,
+		loFlags:    LoFlagsAutoClear,
+	}
+
+	if err := ioctlLoopSetStatus64(loopFile.Fd(), loopInfo); err != nil {
+		log.Errorf("Cannot set up loopback device info: %s", err)
+
+		// If the call failed, then free the loopback device
+		if err := ioctlLoopClrFd(loopFile.Fd()); err != nil {
+			log.Errorf("Error while cleaning up the loopback device")
+		}
+		loopFile.Close()
+		return nil, ErrAttachLoopbackDevice
+	}
+
+	return loopFile, nil
+}

devicemapper/devmapper.go

@@ -0,0 +1,673 @@
+// +build linux
+
+package devicemapper
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"runtime"
+	"syscall"
+
+	log "github.com/Sirupsen/logrus"
+)
+
+type DevmapperLogger interface {
+	DMLog(level int, file string, line int, dmError int, message string)
+}
+
+const (
+	DeviceCreate TaskType = iota
+	DeviceReload
+	DeviceRemove
+	DeviceRemoveAll
+	DeviceSuspend
+	DeviceResume
+	DeviceInfo
+	DeviceDeps
+	DeviceRename
+	DeviceVersion
+	DeviceStatus
+	DeviceTable
+	DeviceWaitevent
+	DeviceList
+	DeviceClear
+	DeviceMknodes
+	DeviceListVersions
+	DeviceTargetMsg
+	DeviceSetGeometry
+)
+
+const (
+	AddNodeOnResume AddNodeType = iota
+	AddNodeOnCreate
+)
+
+var (
+	ErrTaskRun                = errors.New("dm_task_run failed")
+	ErrTaskSetName            = errors.New("dm_task_set_name failed")
+	ErrTaskSetMessage         = errors.New("dm_task_set_message failed")
+	ErrTaskSetAddNode         = errors.New("dm_task_set_add_node failed")
+	ErrTaskSetRo              = errors.New("dm_task_set_ro failed")
+	ErrTaskAddTarget          = errors.New("dm_task_add_target failed")
+	ErrTaskSetSector          = errors.New("dm_task_set_sector failed")
+	ErrTaskGetDeps            = errors.New("dm_task_get_deps failed")
+	ErrTaskGetInfo            = errors.New("dm_task_get_info failed")
+	ErrTaskGetDriverVersion   = errors.New("dm_task_get_driver_version failed")
+	ErrTaskSetCookie          = errors.New("dm_task_set_cookie failed")
+	ErrNilCookie              = errors.New("cookie ptr can't be nil")
+	ErrAttachLoopbackDevice   = errors.New("loopback mounting failed")
+	ErrGetBlockSize           = errors.New("Can't get block size")
+	ErrUdevWait               = errors.New("wait on udev cookie failed")
+	ErrSetDevDir              = errors.New("dm_set_dev_dir failed")
+	ErrGetLibraryVersion      = errors.New("dm_get_library_version failed")
+	ErrCreateRemoveTask       = errors.New("Can't create task of type DeviceRemove")
+	ErrRunRemoveDevice        = errors.New("running removeDevice failed")
+	ErrInvalidAddNode         = errors.New("Invalide AddNoce type")
+	ErrGetLoopbackBackingFile = errors.New("Unable to get loopback backing file")
+	ErrLoopbackSetCapacity    = errors.New("Unable set loopback capacity")
+	ErrBusy                   = errors.New("Device is Busy")
+
+	dmSawBusy  bool
+	dmSawExist bool
+)
+
+type (
+	Task struct {
+		unmanaged *CDmTask
+	}
+	Deps struct {
+		Count  uint32
+		Filler uint32
+		Device []uint64
+	}
+	Info struct {
+		Exists        int
+		Suspended     int
+		LiveTable     int
+		InactiveTable int
+		OpenCount     int32
+		EventNr       uint32
+		Major         uint32
+		Minor         uint32
+		ReadOnly      int
+		TargetCount   int32
+	}
+	TaskType    int
+	AddNodeType int
+)
+
+func (t *Task) destroy() {
+	if t != nil {
+		DmTaskDestroy(t.unmanaged)
+		runtime.SetFinalizer(t, nil)
+	}
+}
+
+func TaskCreate(tasktype TaskType) *Task {
+	Ctask := DmTaskCreate(int(tasktype))
+	if Ctask == nil {
+		return nil
+	}
+	task := &Task{unmanaged: Ctask}
+	runtime.SetFinalizer(task, (*Task).destroy)
+	return task
+}
+
+func (t *Task) Run() error {
+	if res := DmTaskRun(t.unmanaged); res != 1 {
+		return ErrTaskRun
+	}
+	return nil
+}
+
+func (t *Task) SetName(name string) error {
+	if res := DmTaskSetName(t.unmanaged, name); res != 1 {
+		return ErrTaskSetName
+	}
+	return nil
+}
+
+func (t *Task) SetMessage(message string) error {
+	if res := DmTaskSetMessage(t.unmanaged, message); res != 1 {
+		return ErrTaskSetMessage
+	}
+	return nil
+}
+
+func (t *Task) SetSector(sector uint64) error {
+	if res := DmTaskSetSector(t.unmanaged, sector); res != 1 {
+		return ErrTaskSetSector
+	}
+	return nil
+}
+
+func (t *Task) SetCookie(cookie *uint, flags uint16) error {
+	if cookie == nil {
+		return ErrNilCookie
+	}
+	if res := DmTaskSetCookie(t.unmanaged, cookie, flags); res != 1 {
+		return ErrTaskSetCookie
+	}
+	return nil
+}
+
+func (t *Task) SetAddNode(addNode AddNodeType) error {
+	if addNode != AddNodeOnResume && addNode != AddNodeOnCreate {
+		return ErrInvalidAddNode
+	}
+	if res := DmTaskSetAddNode(t.unmanaged, addNode); res != 1 {
+		return ErrTaskSetAddNode
+	}
+	return nil
+}
+
+func (t *Task) SetRo() error {
+	if res := DmTaskSetRo(t.unmanaged); res != 1 {
+		return ErrTaskSetRo
+	}
+	return nil
+}
+
+func (t *Task) AddTarget(start, size uint64, ttype, params string) error {
+	if res := DmTaskAddTarget(t.unmanaged, start, size,
+		ttype, params); res != 1 {
+		return ErrTaskAddTarget
+	}
+	return nil
+}
+
+func (t *Task) GetDeps() (*Deps, error) {
+	var deps *Deps
+	if deps = DmTaskGetDeps(t.unmanaged); deps == nil {
+		return nil, ErrTaskGetDeps
+	}
+	return deps, nil
+}
+
+func (t *Task) GetInfo() (*Info, error) {
+	info := &Info{}
+	if res := DmTaskGetInfo(t.unmanaged, info); res != 1 {
+		return nil, ErrTaskGetInfo
+	}
+	return info, nil
+}
+
+func (t *Task) GetDriverVersion() (string, error) {
+	res := DmTaskGetDriverVersion(t.unmanaged)
+	if res == "" {
+		return "", ErrTaskGetDriverVersion
+	}
+	return res, nil
+}
+
+func (t *Task) GetNextTarget(next uintptr) (nextPtr uintptr, start uint64,
+	length uint64, targetType string, params string) {
+
+	return DmGetNextTarget(t.unmanaged, next, &start, &length,
+			&targetType, &params),
+		start, length, targetType, params
+}
+
+func getLoopbackBackingFile(file *os.File) (uint64, uint64, error) {
+	loopInfo, err := ioctlLoopGetStatus64(file.Fd())
+	if err != nil {
+		log.Errorf("Error get loopback backing file: %s", err)
+		return 0, 0, ErrGetLoopbackBackingFile
+	}
+	return loopInfo.loDevice, loopInfo.loInode, nil
+}
+
+func LoopbackSetCapacity(file *os.File) error {
+	if err := ioctlLoopSetCapacity(file.Fd(), 0); err != nil {
+		log.Errorf("Error loopbackSetCapacity: %s", err)
+		return ErrLoopbackSetCapacity
+	}
+	return nil
+}
+
+func FindLoopDeviceFor(file *os.File) *os.File {
+	stat, err := file.Stat()
+	if err != nil {
+		return nil
+	}
+	targetInode := stat.Sys().(*syscall.Stat_t).Ino
+	targetDevice := stat.Sys().(*syscall.Stat_t).Dev
+
+	for i := 0; true; i++ {
+		path := fmt.Sprintf("/dev/loop%d", i)
+
+		file, err := os.OpenFile(path, os.O_RDWR, 0)
+		if err != nil {
+			if os.IsNotExist(err) {
+				return nil
+			}
+
+			// Ignore all errors until the first not-exist
+			// we want to continue looking for the file
+			continue
+		}
+
+		dev, inode, err := getLoopbackBackingFile(file)
+		if err == nil && dev == targetDevice && inode == targetInode {
+			return file
+		}
+		file.Close()
+	}
+
+	return nil
+}
+
+func UdevWait(cookie uint) error {
+	if res := DmUdevWait(cookie); res != 1 {
+		log.Debugf("Failed to wait on udev cookie %d", cookie)
+		return ErrUdevWait
+	}
+	return nil
+}
+
+func LogInitVerbose(level int) {
+	DmLogInitVerbose(level)
+}
+
+var dmLogger DevmapperLogger = nil
+
+// initialize the logger for the device mapper library
+func LogInit(logger DevmapperLogger) {
+	dmLogger = logger
+	LogWithErrnoInit()
+}
+
+func SetDevDir(dir string) error {
+	if res := DmSetDevDir(dir); res != 1 {
+		log.Debugf("Error dm_set_dev_dir")
+		return ErrSetDevDir
+	}
+	return nil
+}
+
+func GetLibraryVersion() (string, error) {
+	var version string
+	if res := DmGetLibraryVersion(&version); res != 1 {
+		return "", ErrGetLibraryVersion
+	}
+	return version, nil
+}
+
+// Useful helper for cleanup
+func RemoveDevice(name string) error {
+	// TODO(vbatts) just use the other removeDevice()
+	task := TaskCreate(DeviceRemove)
+	if task == nil {
+		return ErrCreateRemoveTask
+	}
+	if err := task.SetName(name); err != nil {
+		log.Debugf("Can't set task name %s", name)
+		return err
+	}
+	if err := task.Run(); err != nil {
+		return ErrRunRemoveDevice
+	}
+	return nil
+}
+
+func GetBlockDeviceSize(file *os.File) (uint64, error) {
+	size, err := ioctlBlkGetSize64(file.Fd())
+	if err != nil {
+		log.Errorf("Error getblockdevicesize: %s", err)
+		return 0, ErrGetBlockSize
+	}
+	return uint64(size), nil
+}
+
+func BlockDeviceDiscard(path string) error {
+	file, err := os.OpenFile(path, os.O_RDWR, 0)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	size, err := GetBlockDeviceSize(file)
+	if err != nil {
+		return err
+	}
+
+	if err := ioctlBlkDiscard(file.Fd(), 0, size); err != nil {
+		return err
+	}
+
+	// Without this sometimes the remove of the device that happens after
+	// discard fails with EBUSY.
+	syscall.Sync()
+
+	return nil
+}
+
+// This is the programmatic example of "dmsetup create"
+func CreatePool(poolName string, dataFile, metadataFile *os.File, poolBlockSize uint32) error {
+	task, err := createTask(DeviceCreate, poolName)
+	if task == nil {
+		return err
+	}
+
+	size, err := GetBlockDeviceSize(dataFile)
+	if err != nil {
+		return fmt.Errorf("Can't get data size %s", err)
+	}
+
+	params := fmt.Sprintf("%s %s %d 32768 1 skip_block_zeroing", metadataFile.Name(), dataFile.Name(), poolBlockSize)
+	if err := task.AddTarget(0, size/512, "thin-pool", params); err != nil {
+		return fmt.Errorf("Can't add target %s", err)
+	}
+
+	var cookie uint = 0
+	if err := task.SetCookie(&cookie, 0); err != nil {
+		return fmt.Errorf("Can't set cookie %s", err)
+	}
+
+	if err := task.Run(); err != nil {
+		return fmt.Errorf("Error running DeviceCreate (CreatePool) %s", err)
+	}
+
+	UdevWait(cookie)
+
+	return nil
+}
+
+func ReloadPool(poolName string, dataFile, metadataFile *os.File, poolBlockSize uint32) error {
+	task, err := createTask(DeviceReload, poolName)
+	if task == nil {
+		return err
+	}
+
+	size, err := GetBlockDeviceSize(dataFile)
+	if err != nil {
+		return fmt.Errorf("Can't get data size %s", err)
+	}
+
+	params := fmt.Sprintf("%s %s %d 32768 1 skip_block_zeroing", metadataFile.Name(), dataFile.Name(), poolBlockSize)
+	if err := task.AddTarget(0, size/512, "thin-pool", params); err != nil {
+		return fmt.Errorf("Can't add target %s", err)
+	}
+
+	if err := task.Run(); err != nil {
+		return fmt.Errorf("Error running DeviceCreate %s", err)
+	}
+
+	return nil
+}
+
+func createTask(t TaskType, name string) (*Task, error) {
+	task := TaskCreate(t)
+	if task == nil {
+		return nil, fmt.Errorf("Can't create task of type %d", int(t))
+	}
+	if err := task.SetName(name); err != nil {
+		return nil, fmt.Errorf("Can't set task name %s", name)
+	}
+	return task, nil
+}
+
+func GetDeps(name string) (*Deps, error) {
+	task, err := createTask(DeviceDeps, name)
+	if task == nil {
+		return nil, err
+	}
+	if err := task.Run(); err != nil {
+		return nil, err
+	}
+	return task.GetDeps()
+}
+
+func GetInfo(name string) (*Info, error) {
+	task, err := createTask(DeviceInfo, name)
+	if task == nil {
+		return nil, err
+	}
+	if err := task.Run(); err != nil {
+		return nil, err
+	}
+	return task.GetInfo()
+}
+
+func GetDriverVersion() (string, error) {
+	task := TaskCreate(DeviceVersion)
+	if task == nil {
+		return "", fmt.Errorf("Can't create DeviceVersion task")
+	}
+	if err := task.Run(); err != nil {
+		return "", err
+	}
+	return task.GetDriverVersion()
+}
+
+func GetStatus(name string) (uint64, uint64, string, string, error) {
+	task, err := createTask(DeviceStatus, name)
+	if task == nil {
+		log.Debugf("GetStatus: Error createTask: %s", err)
+		return 0, 0, "", "", err
+	}
+	if err := task.Run(); err != nil {
+		log.Debugf("GetStatus: Error Run: %s", err)
+		return 0, 0, "", "", err
+	}
+
+	devinfo, err := task.GetInfo()
+	if err != nil {
+		log.Debugf("GetStatus: Error GetInfo: %s", err)
+		return 0, 0, "", "", err
+	}
+	if devinfo.Exists == 0 {
+		log.Debugf("GetStatus: Non existing device %s", name)
+		return 0, 0, "", "", fmt.Errorf("Non existing device %s", name)
+	}
+
+	_, start, length, targetType, params := task.GetNextTarget(0)
+	return start, length, targetType, params, nil
+}
+
+func SetTransactionId(poolName string, oldId uint64, newId uint64) error {
+	task, err := createTask(DeviceTargetMsg, poolName)
+	if task == nil {
+		return err
+	}
+
+	if err := task.SetSector(0); err != nil {
+		return fmt.Errorf("Can't set sector %s", err)
+	}
+
+	if err := task.SetMessage(fmt.Sprintf("set_transaction_id %d %d", oldId, newId)); err != nil {
+		return fmt.Errorf("Can't set message %s", err)
+	}
+
+	if err := task.Run(); err != nil {
+		return fmt.Errorf("Error running SetTransactionId %s", err)
+	}
+	return nil
+}
+
+func SuspendDevice(name string) error {
+	task, err := createTask(DeviceSuspend, name)
+	if task == nil {
+		return err
+	}
+	if err := task.Run(); err != nil {
+		return fmt.Errorf("Error running DeviceSuspend %s", err)
+	}
+	return nil
+}
+
+func ResumeDevice(name string) error {
+	task, err := createTask(DeviceResume, name)
+	if task == nil {
+		return err
+	}
+
+	var cookie uint = 0
+	if err := task.SetCookie(&cookie, 0); err != nil {
+		return fmt.Errorf("Can't set cookie %s", err)
+	}
+
+	if err := task.Run(); err != nil {
+		return fmt.Errorf("Error running DeviceResume %s", err)
+	}
+
+	UdevWait(cookie)
+
+	return nil
+}
+
+func CreateDevice(poolName string, deviceId *int) error {
+	log.Debugf("[devmapper] CreateDevice(poolName=%v, deviceId=%v)", poolName, *deviceId)
+
+	for {
+		task, err := createTask(DeviceTargetMsg, poolName)
+		if task == nil {
+			return err
+		}
+
+		if err := task.SetSector(0); err != nil {
+			return fmt.Errorf("Can't set sector %s", err)
+		}
+
+		if err := task.SetMessage(fmt.Sprintf("create_thin %d", *deviceId)); err != nil {
+			return fmt.Errorf("Can't set message %s", err)
+		}
+
+		dmSawExist = false
+		if err := task.Run(); err != nil {
+			if dmSawExist {
+				// Already exists, try next id
+				*deviceId++
+				continue
+			}
+			return fmt.Errorf("Error running CreateDevice %s", err)
+		}
+		break
+	}
+	return nil
+}
+
+func DeleteDevice(poolName string, deviceId int) error {
+	task, err := createTask(DeviceTargetMsg, poolName)
+	if task == nil {
+		return err
+	}
+
+	if err := task.SetSector(0); err != nil {
+		return fmt.Errorf("Can't set sector %s", err)
+	}
+
+	if err := task.SetMessage(fmt.Sprintf("delete %d", deviceId)); err != nil {
+		return fmt.Errorf("Can't set message %s", err)
+	}
+
+	if err := task.Run(); err != nil {
+		return fmt.Errorf("Error running DeleteDevice %s", err)
+	}
+	return nil
+}
+
+func removeDevice(name string) error {
+	log.Debugf("[devmapper] RemoveDevice START")
+	defer log.Debugf("[devmapper] RemoveDevice END")
+	task, err := createTask(DeviceRemove, name)
+	if task == nil {
+		return err
+	}
+	dmSawBusy = false
+	if err = task.Run(); err != nil {
+		if dmSawBusy {
+			return ErrBusy
+		}
+		return fmt.Errorf("Error running RemoveDevice %s", err)
+	}
+	return nil
+}
+
+func ActivateDevice(poolName string, name string, deviceId int, size uint64) error {
+	task, err := createTask(DeviceCreate, name)
+	if task == nil {
+		return err
+	}
+
+	params := fmt.Sprintf("%s %d", poolName, deviceId)
+	if err := task.AddTarget(0, size/512, "thin", params); err != nil {
+		return fmt.Errorf("Can't add target %s", err)
+	}
+	if err := task.SetAddNode(AddNodeOnCreate); err != nil {
+		return fmt.Errorf("Can't add node %s", err)
+	}
+
+	var cookie uint = 0
+	if err := task.SetCookie(&cookie, 0); err != nil {
+		return fmt.Errorf("Can't set cookie %s", err)
+	}
+
+	if err := task.Run(); err != nil {
+		return fmt.Errorf("Error running DeviceCreate (ActivateDevice) %s", err)
+	}
+
+	UdevWait(cookie)
+
+	return nil
+}
+
+func CreateSnapDevice(poolName string, deviceId *int, baseName string, baseDeviceId int) error {
+	devinfo, _ := GetInfo(baseName)
+	doSuspend := devinfo != nil && devinfo.Exists != 0
+
+	if doSuspend {
+		if err := SuspendDevice(baseName); err != nil {
+			return err
+		}
+	}
+
+	for {
+		task, err := createTask(DeviceTargetMsg, poolName)
+		if task == nil {
+			if doSuspend {
+				ResumeDevice(baseName)
+			}
+			return err
+		}
+
+		if err := task.SetSector(0); err != nil {
+			if doSuspend {
+				ResumeDevice(baseName)
+			}
+			return fmt.Errorf("Can't set sector %s", err)
+		}
+
+		if err := task.SetMessage(fmt.Sprintf("create_snap %d %d", *deviceId, baseDeviceId)); err != nil {
+			if doSuspend {
+				ResumeDevice(baseName)
+			}
+			return fmt.Errorf("Can't set message %s", err)
+		}
+
+		dmSawExist = false
+		if err := task.Run(); err != nil {
+			if dmSawExist {
+				// Already exists, try next id
+				*deviceId++
+				continue
+			}
+
+			if doSuspend {
+				ResumeDevice(baseName)
+			}
+			return fmt.Errorf("Error running DeviceCreate (createSnapDevice) %s", err)
+		}
+
+		break
+	}
+
+	if doSuspend {
+		if err := ResumeDevice(baseName); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

devicemapper/devmapper_log.go

@@ -0,0 +1,30 @@
+// +build linux
+
+package devicemapper
+
+import "C"
+
+import (
+	"strings"
+)
+
+// Due to the way cgo works this has to be in a separate file, as devmapper.go has
+// definitions in the cgo block, which is incompatible with using "//export"
+
+//export DevmapperLogCallback
+func DevmapperLogCallback(level C.int, file *C.char, line C.int, dm_errno_or_class C.int, message *C.char) {
+	msg := C.GoString(message)
+	if level < 7 {
+		if strings.Contains(msg, "busy") {
+			dmSawBusy = true
+		}
+
+		if strings.Contains(msg, "File exists") {
+			dmSawExist = true
+		}
+	}
+
+	if dmLogger != nil {
+		dmLogger.DMLog(int(level), C.GoString(file), int(line), int(dm_errno_or_class), msg)
+	}
+}

devicemapper/devmapper_wrapper.go

@@ -0,0 +1,254 @@
+// +build linux
+
+package devicemapper
+
+/*
+#cgo LDFLAGS: -L. -ldevmapper
+#include <libdevmapper.h>
+#include <linux/loop.h> // FIXME: present only for defines, maybe we can remove it?
+#include <linux/fs.h>   // FIXME: present only for BLKGETSIZE64, maybe we can remove it?
+
+#ifndef LOOP_CTL_GET_FREE
+  #define LOOP_CTL_GET_FREE 0x4C82
+#endif
+
+#ifndef LO_FLAGS_PARTSCAN
+  #define LO_FLAGS_PARTSCAN 8
+#endif
+
+// FIXME: Can't we find a way to do the logging in pure Go?
+extern void DevmapperLogCallback(int level, char *file, int line, int dm_errno_or_class, char *str);
+
+static void	log_cb(int level, const char *file, int line, int dm_errno_or_class, const char *f, ...)
+{
+  char buffer[256];
+  va_list ap;
+
+  va_start(ap, f);
+  vsnprintf(buffer, 256, f, ap);
+  va_end(ap);
+
+  DevmapperLogCallback(level, (char *)file, line, dm_errno_or_class, buffer);
+}
+
+static void	log_with_errno_init()
+{
+  dm_log_with_errno_init(log_cb);
+}
+*/
+import "C"
+
+import "unsafe"
+
+type (
+	CDmTask C.struct_dm_task
+
+	CLoopInfo64 C.struct_loop_info64
+	LoopInfo64  struct {
+		loDevice           uint64 /* ioctl r/o */
+		loInode            uint64 /* ioctl r/o */
+		loRdevice          uint64 /* ioctl r/o */
+		loOffset           uint64
+		loSizelimit        uint64 /* bytes, 0 == max available */
+		loNumber           uint32 /* ioctl r/o */
+		loEncrypt_type     uint32
+		loEncrypt_key_size uint32 /* ioctl w/o */
+		loFlags            uint32 /* ioctl r/o */
+		loFileName         [LoNameSize]uint8
+		loCryptName        [LoNameSize]uint8
+		loEncryptKey       [LoKeySize]uint8 /* ioctl w/o */
+		loInit             [2]uint64
+	}
+)
+
+// IOCTL consts
+const (
+	BlkGetSize64 = C.BLKGETSIZE64
+	BlkDiscard   = C.BLKDISCARD
+
+	LoopSetFd       = C.LOOP_SET_FD
+	LoopCtlGetFree  = C.LOOP_CTL_GET_FREE
+	LoopGetStatus64 = C.LOOP_GET_STATUS64
+	LoopSetStatus64 = C.LOOP_SET_STATUS64
+	LoopClrFd       = C.LOOP_CLR_FD
+	LoopSetCapacity = C.LOOP_SET_CAPACITY
+)
+
+const (
+	LoFlagsAutoClear = C.LO_FLAGS_AUTOCLEAR
+	LoFlagsReadOnly  = C.LO_FLAGS_READ_ONLY
+	LoFlagsPartScan  = C.LO_FLAGS_PARTSCAN
+	LoKeySize        = C.LO_KEY_SIZE
+	LoNameSize       = C.LO_NAME_SIZE
+)
+
+var (
+	DmGetLibraryVersion    = dmGetLibraryVersionFct
+	DmGetNextTarget        = dmGetNextTargetFct
+	DmLogInitVerbose       = dmLogInitVerboseFct
+	DmSetDevDir            = dmSetDevDirFct
+	DmTaskAddTarget        = dmTaskAddTargetFct
+	DmTaskCreate           = dmTaskCreateFct
+	DmTaskDestroy          = dmTaskDestroyFct
+	DmTaskGetDeps          = dmTaskGetDepsFct
+	DmTaskGetInfo          = dmTaskGetInfoFct
+	DmTaskGetDriverVersion = dmTaskGetDriverVersionFct
+	DmTaskRun              = dmTaskRunFct
+	DmTaskSetAddNode       = dmTaskSetAddNodeFct
+	DmTaskSetCookie        = dmTaskSetCookieFct
+	DmTaskSetMessage       = dmTaskSetMessageFct
+	DmTaskSetName          = dmTaskSetNameFct
+	DmTaskSetRo            = dmTaskSetRoFct
+	DmTaskSetSector        = dmTaskSetSectorFct
+	DmUdevWait             = dmUdevWaitFct
+	LogWithErrnoInit       = logWithErrnoInitFct
+)
+
+func free(p *C.char) {
+	C.free(unsafe.Pointer(p))
+}
+
+func dmTaskDestroyFct(task *CDmTask) {
+	C.dm_task_destroy((*C.struct_dm_task)(task))
+}
+
+func dmTaskCreateFct(taskType int) *CDmTask {
+	return (*CDmTask)(C.dm_task_create(C.int(taskType)))
+}
+
+func dmTaskRunFct(task *CDmTask) int {
+	ret, _ := C.dm_task_run((*C.struct_dm_task)(task))
+	return int(ret)
+}
+
+func dmTaskSetNameFct(task *CDmTask, name string) int {
+	Cname := C.CString(name)
+	defer free(Cname)
+
+	return int(C.dm_task_set_name((*C.struct_dm_task)(task), Cname))
+}
+
+func dmTaskSetMessageFct(task *CDmTask, message string) int {
+	Cmessage := C.CString(message)
+	defer free(Cmessage)
+
+	return int(C.dm_task_set_message((*C.struct_dm_task)(task), Cmessage))
+}
+
+func dmTaskSetSectorFct(task *CDmTask, sector uint64) int {
+	return int(C.dm_task_set_sector((*C.struct_dm_task)(task), C.uint64_t(sector)))
+}
+
+func dmTaskSetCookieFct(task *CDmTask, cookie *uint, flags uint16) int {
+	cCookie := C.uint32_t(*cookie)
+	defer func() {
+		*cookie = uint(cCookie)
+	}()
+	return int(C.dm_task_set_cookie((*C.struct_dm_task)(task), &cCookie, C.uint16_t(flags)))
+}
+
+func dmTaskSetAddNodeFct(task *CDmTask, addNode AddNodeType) int {
+	return int(C.dm_task_set_add_node((*C.struct_dm_task)(task), C.dm_add_node_t(addNode)))
+}
+
+func dmTaskSetRoFct(task *CDmTask) int {
+	return int(C.dm_task_set_ro((*C.struct_dm_task)(task)))
+}
+
+func dmTaskAddTargetFct(task *CDmTask,
+	start, size uint64, ttype, params string) int {
+
+	Cttype := C.CString(ttype)
+	defer free(Cttype)
+
+	Cparams := C.CString(params)
+	defer free(Cparams)
+
+	return int(C.dm_task_add_target((*C.struct_dm_task)(task), C.uint64_t(start), C.uint64_t(size), Cttype, Cparams))
+}
+
+func dmTaskGetDepsFct(task *CDmTask) *Deps {
+	Cdeps := C.dm_task_get_deps((*C.struct_dm_task)(task))
+	if Cdeps == nil {
+		return nil
+	}
+	deps := &Deps{
+		Count:  uint32(Cdeps.count),
+		Filler: uint32(Cdeps.filler),
+	}
+	for _, device := range Cdeps.device {
+		deps.Device = append(deps.Device, (uint64)(device))
+	}
+	return deps
+}
+
+func dmTaskGetInfoFct(task *CDmTask, info *Info) int {
+	Cinfo := C.struct_dm_info{}
+	defer func() {
+		info.Exists = int(Cinfo.exists)
+		info.Suspended = int(Cinfo.suspended)
+		info.LiveTable = int(Cinfo.live_table)
+		info.InactiveTable = int(Cinfo.inactive_table)
+		info.OpenCount = int32(Cinfo.open_count)
+		info.EventNr = uint32(Cinfo.event_nr)
+		info.Major = uint32(Cinfo.major)
+		info.Minor = uint32(Cinfo.minor)
+		info.ReadOnly = int(Cinfo.read_only)
+		info.TargetCount = int32(Cinfo.target_count)
+	}()
+	return int(C.dm_task_get_info((*C.struct_dm_task)(task), &Cinfo))
+}
+
+func dmTaskGetDriverVersionFct(task *CDmTask) string {
+	buffer := C.malloc(128)
+	defer C.free(buffer)
+	res := C.dm_task_get_driver_version((*C.struct_dm_task)(task), (*C.char)(buffer), 128)
+	if res == 0 {
+		return ""
+	}
+	return C.GoString((*C.char)(buffer))
+}
+
+func dmGetNextTargetFct(task *CDmTask, next uintptr, start, length *uint64, target, params *string) uintptr {
+	var (
+		Cstart, Clength      C.uint64_t
+		CtargetType, Cparams *C.char
+	)
+	defer func() {
+		*start = uint64(Cstart)
+		*length = uint64(Clength)
+		*target = C.GoString(CtargetType)
+		*params = C.GoString(Cparams)
+	}()
+
+	nextp := C.dm_get_next_target((*C.struct_dm_task)(task), unsafe.Pointer(next), &Cstart, &Clength, &CtargetType, &Cparams)
+	return uintptr(nextp)
+}
+
+func dmUdevWaitFct(cookie uint) int {
+	return int(C.dm_udev_wait(C.uint32_t(cookie)))
+}
+
+func dmLogInitVerboseFct(level int) {
+	C.dm_log_init_verbose(C.int(level))
+}
+
+func logWithErrnoInitFct() {
+	C.log_with_errno_init()
+}
+
+func dmSetDevDirFct(dir string) int {
+	Cdir := C.CString(dir)
+	defer free(Cdir)
+
+	return int(C.dm_set_dev_dir(Cdir))
+}
+
+func dmGetLibraryVersionFct(version *string) int {
+	buffer := C.CString(string(make([]byte, 128)))
+	defer free(buffer)
+	defer func() {
+		*version = C.GoString(buffer)
+	}()
+	return int(C.dm_get_library_version(buffer, 128))
+}

devicemapper/ioctl.go

@@ -0,0 +1,72 @@
+// +build linux
+
+package devicemapper
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func ioctlLoopCtlGetFree(fd uintptr) (int, error) {
+	index, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, LoopCtlGetFree, 0)
+	if err != 0 {
+		return 0, err
+	}
+	return int(index), nil
+}
+
+func ioctlLoopSetFd(loopFd, sparseFd uintptr) error {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, loopFd, LoopSetFd, sparseFd); err != 0 {
+		return err
+	}
+	return nil
+}
+
+func ioctlLoopSetStatus64(loopFd uintptr, loopInfo *LoopInfo64) error {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, loopFd, LoopSetStatus64, uintptr(unsafe.Pointer(loopInfo))); err != 0 {
+		return err
+	}
+	return nil
+}
+
+func ioctlLoopClrFd(loopFd uintptr) error {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, loopFd, LoopClrFd, 0); err != 0 {
+		return err
+	}
+	return nil
+}
+
+func ioctlLoopGetStatus64(loopFd uintptr) (*LoopInfo64, error) {
+	loopInfo := &LoopInfo64{}
+
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, loopFd, LoopGetStatus64, uintptr(unsafe.Pointer(loopInfo))); err != 0 {
+		return nil, err
+	}
+	return loopInfo, nil
+}
+
+func ioctlLoopSetCapacity(loopFd uintptr, value int) error {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, loopFd, LoopSetCapacity, uintptr(value)); err != 0 {
+		return err
+	}
+	return nil
+}
+
+func ioctlBlkGetSize64(fd uintptr) (int64, error) {
+	var size int64
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, BlkGetSize64, uintptr(unsafe.Pointer(&size))); err != 0 {
+		return 0, err
+	}
+	return size, nil
+}
+
+func ioctlBlkDiscard(fd uintptr, offset, length uint64) error {
+	var r [2]uint64
+	r[0] = offset
+	r[1] = length
+
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, BlkDiscard, uintptr(unsafe.Pointer(&r[0]))); err != 0 {
+		return err
+	}
+	return nil
+}