// +build windows
 

 // Maintainer:  jhowardmsft
 // Locale:      en-gb
 // About:       Graph-driver for Linux Containers On Windows (LCOW)
 //
 // This graphdriver runs in two modes. Yet to be determined which one will
 // be the shipping mode. The global mode is where a single utility VM
 // is used for all service VM tool operations. This isn't safe security-wise
 // as it's attaching a sandbox of multiple containers to it, containing
 // untrusted data. This may be fine for client devops scenarios. In
 // safe mode, a unique utility VM is instantiated for all service VM tool
 // operations. The downside of safe-mode is that operations are slower as
 // a new service utility VM has to be started and torn-down when needed.
 //

 // Options (needs official documentation, but lets get full functionality first...) @jhowardmsft
 //
 // The following options are read by the graphdriver itself:
 //
 //   * lcow.globalmode - Enables global service VM Mode
 //        -- Possible values:     true/false
 //        -- Default if omitted:  false
 //
 //   * lcow.sandboxsize - Specifies a custom sandbox size in GB for starting a container
 //        -- Possible values:      >= default sandbox size (opengcs defined, currently 20)

 //        -- Default if omitted:  20

 //
 // The following options are read by opengcs:
 //
 //   * lcow.kirdpath - Specifies a custom path to a kernel/initrd pair
 //        -- Possible values:      Any local path that is not a mapped drive

 //        -- Default if omitted:  %ProgramFiles%\Linux Containers

 //
 //   * lcow.kernel - Specifies a custom kernel file located in the `lcow.kirdpath` path
 //        -- Possible values:      Any valid filename

 //        -- Default if omitted:  bootx64.efi

 //
 //   * lcow.initrd - Specifies a custom initrd file located in the `lcow.kirdpath` path
 //        -- Possible values:      Any valid filename

 //        -- Default if omitted:  initrd.img

 //
 //   * lcow.bootparameters - Specifies additional boot parameters for booting in kernel+initrd mode
 //        -- Possible values:      Any valid linux kernel boot options

 //        -- Default if omitted:  <nil>

 //
 //   * lcow.vhdx - Specifies a custom vhdx file to boot (instead of a kernel+initrd)
 //        -- Possible values:      Any valid filename

 //        -- Default if omitted:  uvm.vhdx under `lcow.kirdpath`

 //
 //   * lcow.timeout - Specifies a timeout for utility VM operations in seconds
 //        -- Possible values:      >=0

 //        -- Default if omitted:  300

 
 // TODO: Grab logs from SVM at terminate or errors

 package lcow

 
 import (
 	"encoding/json"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"

 	"strconv"

 	"strings"
 	"sync"

 	"syscall"

 	"time"
 

 	"github.com/Microsoft/hcsshim"

 	"github.com/Microsoft/opengcs/client"

 	"github.com/docker/docker/daemon/graphdriver"
 	"github.com/docker/docker/pkg/archive"

 	"github.com/docker/docker/pkg/containerfs"

 	"github.com/docker/docker/pkg/idtools"

 	"github.com/docker/docker/pkg/ioutils"

 	"github.com/docker/docker/pkg/system"

 	"github.com/sirupsen/logrus"

 )
 

 // init registers this driver to the register. It gets initialised by the
 // function passed in the second parameter, implemented in this file.

 func init() {

 	graphdriver.Register("lcow", InitDriver)

 }
 
 const (

 	// sandboxFilename is the name of the file containing a layer's sandbox (read-write layer).

 	sandboxFilename = "sandbox.vhdx"

 	// scratchFilename is the name of the scratch-space used by an SVM to avoid running out of memory.
 	scratchFilename = "scratch.vhdx"
 
 	// layerFilename is the name of the file containing a layer's read-only contents.
 	// Note this really is VHD format, not VHDX.
 	layerFilename = "layer.vhd"
 
 	// toolsScratchPath is a location in a service utility VM that the tools can use as a
 	// scratch space to avoid running out of memory.

 	toolsScratchPath = "/tmp/scratch"

 
 	// svmGlobalID is the ID used in the serviceVMs map for the global service VM when running in "global" mode.
 	svmGlobalID = "_lcow_global_svm_"
 
 	// cacheDirectory is the sub-folder under the driver's data-root used to cache blank sandbox and scratch VHDs.
 	cacheDirectory = "cache"
 
 	// scratchDirectory is the sub-folder under the driver's data-root used for scratch VHDs in service VMs
 	scratchDirectory = "scratch"

 	// errOperationPending is the HRESULT returned by the HCS when the VM termination operation is still pending.
 	errOperationPending syscall.Errno = 0xc0370103
 )

 
 // Driver represents an LCOW graph driver.
 type Driver struct {

 	dataRoot           string     // Root path on the host where we are storing everything.
 	cachedSandboxFile  string     // Location of the local default-sized cached sandbox.
 	cachedSandboxMutex sync.Mutex // Protects race conditions from multiple threads creating the cached sandbox.
 	cachedScratchFile  string     // Location of the local cached empty scratch space.
 	cachedScratchMutex sync.Mutex // Protects race conditions from multiple threads creating the cached scratch.
 	options            []string   // Graphdriver options we are initialised with.
 	globalMode         bool       // Indicates if running in an unsafe/global service VM mode.

 
 	// NOTE: It is OK to use a cache here because Windows does not support

 	// restoring containers when the daemon dies.

 	serviceVms *serviceVMMap // Map of the configs representing the service VM(s) we are running.

 }
 

 // layerDetails is the structure returned by a helper function `getLayerDetails`
 // for getting information about a layer folder
 type layerDetails struct {
 	filename  string // \path\to\sandbox.vhdx or \path\to\layer.vhd
 	size      int64  // size of the above file
 	isSandbox bool   // true if sandbox.vhdx
 }
 

 // deletefiles is a helper function for initialisation where we delete any
 // left-over scratch files in case we were previously forcibly terminated.
 func deletefiles(path string, f os.FileInfo, err error) error {
 	if strings.HasSuffix(f.Name(), ".vhdx") {
 		logrus.Warnf("lcowdriver: init: deleting stale scratch file %s", path)
 		return os.Remove(path)
 	}
 	return nil
 }
 
 // InitDriver returns a new LCOW storage driver.
 func InitDriver(dataRoot string, options []string, _, _ []idtools.IDMap) (graphdriver.Driver, error) {

 	title := "lcowdriver: init:"

 
 	cd := filepath.Join(dataRoot, cacheDirectory)
 	sd := filepath.Join(dataRoot, scratchDirectory)

 
 	d := &Driver{

 		dataRoot:          dataRoot,
 		options:           options,
 		cachedSandboxFile: filepath.Join(cd, sandboxFilename),
 		cachedScratchFile: filepath.Join(cd, scratchFilename),

 		serviceVms: &serviceVMMap{
 			svms: make(map[string]*serviceVMMapItem),
 		},
 		globalMode: false,

 	}
 
 	// Looks for relevant options
 	for _, v := range options {
 		opt := strings.SplitN(v, "=", 2)
 		if len(opt) == 2 {
 			switch strings.ToLower(opt[0]) {
 			case "lcow.globalmode":
 				var err error
 				d.globalMode, err = strconv.ParseBool(opt[1])
 				if err != nil {
 					return nil, fmt.Errorf("%s failed to parse value for 'lcow.globalmode' - must be 'true' or 'false'", title)
 				}
 				break
 			}
 		}

 	}
 

 	// Make sure the dataRoot directory is created
 	if err := idtools.MkdirAllAs(dataRoot, 0700, 0, 0); err != nil {
 		return nil, fmt.Errorf("%s failed to create '%s': %v", title, dataRoot, err)

 	}
 

 	// Make sure the cache directory is created under dataRoot
 	if err := idtools.MkdirAllAs(cd, 0700, 0, 0); err != nil {
 		return nil, fmt.Errorf("%s failed to create '%s': %v", title, cd, err)

 	}
 

 	// Make sure the scratch directory is created under dataRoot
 	if err := idtools.MkdirAllAs(sd, 0700, 0, 0); err != nil {
 		return nil, fmt.Errorf("%s failed to create '%s': %v", title, sd, err)

 	}
 

 	// Delete any items in the scratch directory
 	filepath.Walk(sd, deletefiles)
 
 	logrus.Infof("%s dataRoot: %s globalMode: %t", title, dataRoot, d.globalMode)
 

 	return d, nil
 }
 

 func (d *Driver) getVMID(id string) string {
 	if d.globalMode {
 		return svmGlobalID
 	}
 	return id
 }
 

 // startServiceVMIfNotRunning starts a service utility VM if it is not currently running.
 // It can optionally be started with a mapped virtual disk. Returns a opengcs config structure
 // representing the VM.

 func (d *Driver) startServiceVMIfNotRunning(id string, mvdToAdd []hcsshim.MappedVirtualDisk, context string) (_ *serviceVM, err error) {

 	// Use the global ID if in global mode

 	id = d.getVMID(id)

 
 	title := fmt.Sprintf("lcowdriver: startservicevmifnotrunning %s:", id)

 	// Attempt to add ID to the service vm map
 	logrus.Debugf("%s: Adding entry to service vm map", title)
 	svm, exists, err := d.serviceVms.add(id)
 	if err != nil && err == errVMisTerminating {
 		// VM is in the process of terminating. Wait until it's done and and then try again
 		logrus.Debugf("%s: VM with current ID still in the process of terminating: %s", title, id)
 		if err := svm.getStopError(); err != nil {
 			logrus.Debugf("%s: VM %s did not stop succesfully: %s", title, id, err)
 			return nil, err
 		}
 		return d.startServiceVMIfNotRunning(id, mvdToAdd, context)
 	} else if err != nil {
 		logrus.Debugf("%s: failed to add service vm to map: %s", err)
 		return nil, fmt.Errorf("%s: failed to add to service vm map: %s", title, err)
 	}

 	if exists {
 		// Service VM is already up and running. In this case, just hot add the vhds.
 		logrus.Debugf("%s: service vm already exists. Just hot adding: %+v", title, mvdToAdd)
 		if err := svm.hotAddVHDs(mvdToAdd...); err != nil {
 			logrus.Debugf("%s: failed to hot add vhds on service vm creation: %s", title, err)
 			return nil, fmt.Errorf("%s: failed to hot add vhds on service vm: %s", title, err)

 		}
 		return svm, nil
 	}
 

 	// We are the first service for this id, so we need to start it
 	logrus.Debugf("%s: service vm doesn't exist. Now starting it up: %s", title, id)

 	defer func() {
 		// Signal that start has finished, passing in the error if any.
 		svm.signalStartFinished(err)
 		if err != nil {
 			// We added a ref to the VM, since we failed, we should delete the ref.
 			d.terminateServiceVM(id, "error path on startServiceVMIfNotRunning", false)
 		}
 	}()

 	// Generate a default configuration
 	if err := svm.config.GenerateDefault(d.options); err != nil {
 		return nil, fmt.Errorf("%s failed to generate default gogcs configuration for global svm (%s): %s", title, context, err)

 	}
 

 	// For the name, we deliberately suffix if safe-mode to ensure that it doesn't
 	// clash with another utility VM which may be running for the container itself.
 	// This also makes it easier to correlate through Get-ComputeProcess.
 	if id == svmGlobalID {
 		svm.config.Name = svmGlobalID
 	} else {
 		svm.config.Name = fmt.Sprintf("%s_svm", id)
 	}
 
 	// Ensure we take the cached scratch mutex around the check to ensure the file is complete
 	// and not in the process of being created by another thread.
 	scratchTargetFile := filepath.Join(d.dataRoot, scratchDirectory, fmt.Sprintf("%s.vhdx", id))
 
 	logrus.Debugf("%s locking cachedScratchMutex", title)
 	d.cachedScratchMutex.Lock()
 	if _, err := os.Stat(d.cachedScratchFile); err == nil {
 		// Make a copy of cached scratch to the scratch directory
 		logrus.Debugf("lcowdriver: startServiceVmIfNotRunning: (%s) cloning cached scratch for mvd", context)
 		if err := client.CopyFile(d.cachedScratchFile, scratchTargetFile, true); err != nil {
 			logrus.Debugf("%s releasing cachedScratchMutex on err: %s", title, err)
 			d.cachedScratchMutex.Unlock()
 			return nil, err
 		}
 
 		// Add the cached clone as a mapped virtual disk
 		logrus.Debugf("lcowdriver: startServiceVmIfNotRunning: (%s) adding cloned scratch as mvd", context)

 		mvd := hcsshim.MappedVirtualDisk{

 			HostPath:          scratchTargetFile,

 			ContainerPath:     toolsScratchPath,
 			CreateInUtilityVM: true,
 		}

 		svm.config.MappedVirtualDisks = append(svm.config.MappedVirtualDisks, mvd)
 		svm.scratchAttached = true
 	}

 	logrus.Debugf("%s releasing cachedScratchMutex", title)
 	d.cachedScratchMutex.Unlock()
 
 	// If requested to start it with a mapped virtual disk, add it now.

 	svm.config.MappedVirtualDisks = append(svm.config.MappedVirtualDisks, mvdToAdd...)
 	for _, mvd := range svm.config.MappedVirtualDisks {
 		svm.attachedVHDs[mvd.HostPath] = 1

 	}
 
 	// Start it.
 	logrus.Debugf("lcowdriver: startServiceVmIfNotRunning: (%s) starting %s", context, svm.config.Name)

 	if err := svm.config.StartUtilityVM(); err != nil {

 		return nil, fmt.Errorf("failed to start service utility VM (%s): %s", context, err)
 	}
 

 	// defer function to terminate the VM if the next steps fail
 	defer func() {
 		if err != nil {
 			waitTerminate(svm, fmt.Sprintf("startServiceVmIfNotRunning: %s (%s)", id, context))
 		}
 	}()

 
 	// Now we have a running service VM, we can create the cached scratch file if it doesn't exist.
 	logrus.Debugf("%s locking cachedScratchMutex", title)
 	d.cachedScratchMutex.Lock()
 	if _, err := os.Stat(d.cachedScratchFile); err != nil {

 		logrus.Debugf("%s (%s): creating an SVM scratch", title, context)
 
 		// Don't use svm.CreateExt4Vhdx since that only works when the service vm is setup,
 		// but we're still in that process right now.

 		if err := svm.config.CreateExt4Vhdx(scratchTargetFile, client.DefaultVhdxSizeGB, d.cachedScratchFile); err != nil {

 			logrus.Debugf("%s (%s): releasing cachedScratchMutex on error path", title, context)
 			d.cachedScratchMutex.Unlock()

 			logrus.Debugf("%s: failed to create vm scratch %s: %s", title, scratchTargetFile, err)

 			return nil, fmt.Errorf("failed to create SVM scratch VHDX (%s): %s", context, err)
 		}

 	}

 	logrus.Debugf("%s (%s): releasing cachedScratchMutex", title, context)
 	d.cachedScratchMutex.Unlock()

 
 	// Hot-add the scratch-space if not already attached

 	if !svm.scratchAttached {

 		logrus.Debugf("lcowdriver: startServiceVmIfNotRunning: (%s) hot-adding scratch %s", context, scratchTargetFile)
 		if err := svm.hotAddVHDsAtStart(hcsshim.MappedVirtualDisk{
 			HostPath:          scratchTargetFile,
 			ContainerPath:     toolsScratchPath,
 			CreateInUtilityVM: true,
 		}); err != nil {
 			logrus.Debugf("%s: failed to hot-add scratch %s: %s", title, scratchTargetFile, err)

 			return nil, fmt.Errorf("failed to hot-add %s failed: %s", scratchTargetFile, err)

 		}

 		svm.scratchAttached = true

 	}

 
 	logrus.Debugf("lcowdriver: startServiceVmIfNotRunning: (%s) success", context)
 	return svm, nil

 }
 

 // terminateServiceVM terminates a service utility VM if its running if it's,
 // not being used by any goroutine, but does nothing when in global mode as it's
 // lifetime is limited to that of the daemon. If the force flag is set, then
 // the VM will be killed regardless of the ref count or if it's global.
 func (d *Driver) terminateServiceVM(id, context string, force bool) (err error) {
 	// We don't do anything in safe mode unless the force flag has been passed, which
 	// is only the case for cleanup at driver termination.
 	if d.globalMode && !force {
 		logrus.Debugf("lcowdriver: terminateservicevm: %s (%s) - doing nothing as in global mode", id, context)
 		return nil

 	}
 

 	id = d.getVMID(id)

 	var svm *serviceVM
 	var lastRef bool
 	if !force {
 		// In the not force case, we ref count
 		svm, lastRef, err = d.serviceVms.decrementRefCount(id)
 	} else {
 		// In the force case, we ignore the ref count and just set it to 0
 		svm, err = d.serviceVms.setRefCountZero(id)
 		lastRef = true

 	}

 	if err == errVMUnknown {
 		return nil
 	} else if err == errVMisTerminating {
 		return svm.getStopError()
 	} else if !lastRef {
 		return nil

 	}
 

 	// We run the deletion of the scratch as a deferred function to at least attempt
 	// clean-up in case of errors.
 	defer func() {
 		if svm.scratchAttached {
 			scratchTargetFile := filepath.Join(d.dataRoot, scratchDirectory, fmt.Sprintf("%s.vhdx", id))
 			logrus.Debugf("lcowdriver: terminateservicevm: %s (%s) - deleting scratch %s", id, context, scratchTargetFile)

 			if errRemove := os.Remove(scratchTargetFile); errRemove != nil {
 				logrus.Warnf("failed to remove scratch file %s (%s): %s", scratchTargetFile, context, errRemove)
 				err = errRemove

 			}
 		}

 
 		// This function shouldn't actually return error unless there is a bug
 		if errDelete := d.serviceVms.deleteID(id); errDelete != nil {
 			logrus.Warnf("failed to service vm from svm map %s (%s): %s", id, context, errDelete)
 		}
 
 		// Signal that this VM has stopped
 		svm.signalStopFinished(err)

 	}()
 

 	// Now it's possible that the serivce VM failed to start and now we are trying to termiante it.
 	// In this case, we will relay the error to the goroutines waiting for this vm to stop.
 	if err := svm.getStartError(); err != nil {
 		logrus.Debugf("lcowdriver: terminateservicevm: %s had failed to start up: %s", id, err)
 		return err
 	}
 
 	if err := waitTerminate(svm, fmt.Sprintf("terminateservicevm: %s (%s)", id, context)); err != nil {
 		return err
 	}
 
 	logrus.Debugf("lcowdriver: terminateservicevm: %s (%s) - success", id, context)
 	return nil
 }
 
 func waitTerminate(svm *serviceVM, context string) error {
 	if svm.config == nil {
 		return fmt.Errorf("lcowdriver: waitTermiante: Nil utility VM. %s", context)
 	}
 
 	logrus.Debugf("lcowdriver: waitTerminate: Calling terminate: %s", context)
 	if err := svm.config.Uvm.Terminate(); err != nil {
 		// We might get operation still pending from the HCS. In that case, we shouldn't return
 		// an error since we call wait right after.
 		underlyingError := err
 		if conterr, ok := err.(*hcsshim.ContainerError); ok {
 			underlyingError = conterr.Err

 		}
 

 		if syscallErr, ok := underlyingError.(syscall.Errno); ok {
 			underlyingError = syscallErr
 		}
 
 		if underlyingError != errOperationPending {
 			return fmt.Errorf("failed to terminate utility VM (%s): %s", context, err)

 		}

 		logrus.Debugf("lcowdriver: waitTerminate: uvm.Terminate() returned operation pending (%s)", context)

 	}
 

 	logrus.Debugf("lcowdriver: waitTerminate: (%s) - waiting for utility VM to terminate", context)
 	if err := svm.config.Uvm.WaitTimeout(time.Duration(svm.config.UvmTimeoutSeconds) * time.Second); err != nil {
 		return fmt.Errorf("failed waiting for utility VM to terminate (%s): %s", context, err)
 	}

 	return nil
 }
 
 // String returns the string representation of a driver. This should match
 // the name the graph driver has been registered with.
 func (d *Driver) String() string {
 	return "lcow"
 }
 
 // Status returns the status of the driver.
 func (d *Driver) Status() [][2]string {
 	return [][2]string{
 		{"LCOW", ""},

 		// TODO: Add some more info here - mode, home, ....

 	}
 }
 
 // Exists returns true if the given id is registered with this driver.
 func (d *Driver) Exists(id string) bool {
 	_, err := os.Lstat(d.dir(id))
 	logrus.Debugf("lcowdriver: exists: id %s %t", id, err == nil)
 	return err == nil
 }
 
 // CreateReadWrite creates a layer that is writable for use as a container

 // file system. That equates to creating a sandbox.

 func (d *Driver) CreateReadWrite(id, parent string, opts *graphdriver.CreateOpts) error {

 	title := fmt.Sprintf("lcowdriver: createreadwrite: id %s", id)
 	logrus.Debugf(title)

 	// First we need to create the folder
 	if err := d.Create(id, parent, opts); err != nil {

 		return err
 	}
 

 	// Look for an explicit sandbox size option.
 	sandboxSize := uint64(client.DefaultVhdxSizeGB)
 	for k, v := range opts.StorageOpt {
 		switch strings.ToLower(k) {
 		case "lcow.sandboxsize":
 			var err error
 			sandboxSize, err = strconv.ParseUint(v, 10, 32)
 			if err != nil {
 				return fmt.Errorf("%s failed to parse value '%s' for 'lcow.sandboxsize'", title, v)
 			}
 			if sandboxSize < client.DefaultVhdxSizeGB {
 				return fmt.Errorf("%s 'lcow.sandboxsize' option cannot be less than %d", title, client.DefaultVhdxSizeGB)
 			}
 			break
 		}
 	}
 

 	// Massive perf optimisation here. If we know that the RW layer is the default size,
 	// and that the cached sandbox already exists, and we are running in safe mode, we
 	// can just do a simple copy into the layers sandbox file without needing to start a

 	// unique service VM. For a global service VM, it doesn't really matter. Of course,
 	// this is only the case where the sandbox is the default size.

 	//
 	// Make sure we have the sandbox mutex taken while we are examining it.

 	if sandboxSize == client.DefaultVhdxSizeGB {
 		logrus.Debugf("%s: locking cachedSandboxMutex", title)
 		d.cachedSandboxMutex.Lock()
 		_, err := os.Stat(d.cachedSandboxFile)
 		logrus.Debugf("%s: releasing cachedSandboxMutex", title)
 		d.cachedSandboxMutex.Unlock()
 		if err == nil {
 			logrus.Debugf("%s: using cached sandbox to populate", title)
 			if err := client.CopyFile(d.cachedSandboxFile, filepath.Join(d.dir(id), sandboxFilename), true); err != nil {
 				return err
 			}
 			return nil

 		}
 	}
 
 	logrus.Debugf("%s: creating SVM to create sandbox", title)
 	svm, err := d.startServiceVMIfNotRunning(id, nil, "createreadwrite")
 	if err != nil {
 		return err
 	}
 	defer d.terminateServiceVM(id, "createreadwrite", false)
 

 	// So the sandbox needs creating. If default size ensure we are the only thread populating the cache.
 	// Non-default size we don't store, just create them one-off so no need to lock the cachedSandboxMutex.
 	if sandboxSize == client.DefaultVhdxSizeGB {
 		logrus.Debugf("%s: locking cachedSandboxMutex for creation", title)
 		d.cachedSandboxMutex.Lock()
 		defer func() {
 			logrus.Debugf("%s: releasing cachedSandboxMutex for creation", title)
 			d.cachedSandboxMutex.Unlock()
 		}()
 	}

 	// Make sure we don't write to our local cached copy if this is for a non-default size request.
 	targetCacheFile := d.cachedSandboxFile
 	if sandboxSize != client.DefaultVhdxSizeGB {
 		targetCacheFile = ""
 	}
 

 	// Create the ext4 vhdx
 	logrus.Debugf("%s: creating sandbox ext4 vhdx", title)
 	if err := svm.createExt4VHDX(filepath.Join(d.dir(id), sandboxFilename), uint32(sandboxSize), targetCacheFile); err != nil {
 		logrus.Debugf("%s: failed to create sandbox vhdx for %s: %s", title, id, err)

 		return err
 	}

 	return nil

 }
 

 // Create creates the folder for the layer with the given id, and
 // adds it to the layer chain.

 func (d *Driver) Create(id, parent string, opts *graphdriver.CreateOpts) error {
 	logrus.Debugf("lcowdriver: create: id %s parent: %s", id, parent)
 
 	parentChain, err := d.getLayerChain(parent)
 	if err != nil {
 		return err
 	}
 
 	var layerChain []string
 	if parent != "" {
 		if !d.Exists(parent) {

 			return fmt.Errorf("lcowdriver: cannot create layer folder with missing parent %s", parent)

 		}
 		layerChain = []string{d.dir(parent)}
 	}
 	layerChain = append(layerChain, parentChain...)
 
 	// Make sure layers are created with the correct ACL so that VMs can access them.
 	layerPath := d.dir(id)

 	logrus.Debugf("lcowdriver: create: id %s: creating %s", id, layerPath)

 	if err := system.MkdirAllWithACL(layerPath, 755, system.SddlNtvmAdministratorsLocalSystem); err != nil {
 		return err
 	}
 
 	if err := d.setLayerChain(id, layerChain); err != nil {
 		if err2 := os.RemoveAll(layerPath); err2 != nil {

 			logrus.Warnf("failed to remove layer %s: %s", layerPath, err2)

 		}
 		return err
 	}

 	logrus.Debugf("lcowdriver: create: id %s: success", id)

 
 	return nil
 }
 
 // Remove unmounts and removes the dir information.
 func (d *Driver) Remove(id string) error {
 	logrus.Debugf("lcowdriver: remove: id %s", id)
 	tmpID := fmt.Sprintf("%s-removing", id)
 	tmpLayerPath := d.dir(tmpID)
 	layerPath := d.dir(id)
 
 	logrus.Debugf("lcowdriver: remove: id %s: layerPath %s", id, layerPath)

 
 	// Unmount all the layers
 	err := d.Put(id)
 	if err != nil {
 		logrus.Debugf("lcowdriver: remove id %s: failed to unmount: %s", id, err)
 		return err
 	}
 
 	// for non-global case just kill the vm
 	if !d.globalMode {
 		if err := d.terminateServiceVM(id, fmt.Sprintf("Remove %s", id), true); err != nil {
 			return err
 		}
 	}
 

 	if err := os.Rename(layerPath, tmpLayerPath); err != nil && !os.IsNotExist(err) {
 		return err
 	}
 
 	if err := os.RemoveAll(tmpLayerPath); err != nil {
 		return err
 	}
 
 	logrus.Debugf("lcowdriver: remove: id %s: layerPath %s succeeded", id, layerPath)
 	return nil
 }
 
 // Get returns the rootfs path for the id. It is reference counted and
 // effectively can be thought of as a "mount the layer into the utility

 // vm if it isn't already". The contract from the caller of this is that
 // all Gets and Puts are matched. It -should- be the case that on cleanup,
 // nothing is mounted.
 //
 // For optimisation, we don't actually mount the filesystem (which in our
 // case means [hot-]adding it to a service VM. But we track that and defer
 // the actual adding to the point we need to access it.

 func (d *Driver) Get(id, mountLabel string) (containerfs.ContainerFS, error) {

 	title := fmt.Sprintf("lcowdriver: get: %s", id)
 	logrus.Debugf(title)

 	// Generate the mounts needed for the defered operation.
 	disks, err := d.getAllMounts(id)

 	if err != nil {

 		logrus.Debugf("%s failed to get all layer details for %s: %s", title, d.dir(id), err)
 		return nil, fmt.Errorf("%s failed to get layer details for %s: %s", title, d.dir(id), err)

 	}
 

 	logrus.Debugf("%s: got layer mounts: %+v", title, disks)
 	return &lcowfs{
 		root:        unionMountName(disks),
 		d:           d,
 		mappedDisks: disks,
 		vmID:        d.getVMID(id),
 	}, nil

 }
 
 // Put does the reverse of get. If there are no more references to
 // the layer, it unmounts it from the utility VM.
 func (d *Driver) Put(id string) error {

 	title := fmt.Sprintf("lcowdriver: put: %s", id)

 	// Get the service VM that we need to remove from
 	svm, err := d.serviceVms.get(d.getVMID(id))
 	if err == errVMUnknown {

 		return nil

 	} else if err == errVMisTerminating {
 		return svm.getStopError()

 	}

 	// Generate the mounts that Get() might have mounted
 	disks, err := d.getAllMounts(id)
 	if err != nil {
 		logrus.Debugf("%s failed to get all layer details for %s: %s", title, d.dir(id), err)
 		return fmt.Errorf("%s failed to get layer details for %s: %s", title, d.dir(id), err)
 	}

 	// Now, we want to perform the unmounts, hot-remove and stop the service vm.
 	// We want to go though all the steps even if we have an error to clean up properly
 	err = svm.deleteUnionMount(unionMountName(disks), disks...)
 	if err != nil {
 		logrus.Debugf("%s failed to delete union mount %s: %s", title, id, err)
 	}

 	err1 := svm.hotRemoveVHDs(disks...)
 	if err1 != nil {
 		logrus.Debugf("%s failed to hot remove vhds %s: %s", title, id, err)
 		if err == nil {
 			err = err1

 		}
 	}
 

 	err1 = d.terminateServiceVM(id, fmt.Sprintf("Put %s", id), false)
 	if err1 != nil {
 		logrus.Debugf("%s failed to terminate service vm %s: %s", title, id, err1)
 		if err == nil {
 			err = err1
 		}
 	}
 	logrus.Debugf("Put succeeded on id %s", id)
 	return err

 }
 
 // Cleanup ensures the information the driver stores is properly removed.
 // We use this opportunity to cleanup any -removing folders which may be
 // still left if the daemon was killed while it was removing a layer.
 func (d *Driver) Cleanup() error {
 	title := "lcowdriver: cleanup"
 

 	items, err := ioutil.ReadDir(d.dataRoot)

 	if err != nil {
 		if os.IsNotExist(err) {
 			return nil
 		}
 		return err
 	}
 
 	// Note we don't return an error below - it's possible the files
 	// are locked. However, next time around after the daemon exits,
 	// we likely will be able to to cleanup successfully. Instead we log
 	// warnings if there are errors.
 	for _, item := range items {
 		if item.IsDir() && strings.HasSuffix(item.Name(), "-removing") {

 			if err := os.RemoveAll(filepath.Join(d.dataRoot, item.Name())); err != nil {

 				logrus.Warnf("%s failed to cleanup %s: %s", title, item.Name(), err)
 			} else {
 				logrus.Infof("%s cleaned up %s", title, item.Name())
 			}
 		}
 	}

 
 	// Cleanup any service VMs we have running, along with their scratch spaces.
 	// We don't take the lock for this as it's taken in terminateServiceVm.

 	for k, v := range d.serviceVms.svms {
 		logrus.Debugf("%s svm entry: %s: %+v", title, k, v)

 		d.terminateServiceVM(k, "cleanup", true)
 	}
 

 	return nil
 }
 
 // Diff takes a layer (and it's parent layer which may be null, but
 // is ignored by this implementation below) and returns a reader for
 // a tarstream representing the layers contents. The id could be
 // a read-only "layer.vhd" or a read-write "sandbox.vhdx". The semantics
 // of this function dictate that the layer is already mounted.

 // However, as we do lazy mounting as a performance optimisation,
 // this will likely not be the case.

 func (d *Driver) Diff(id, parent string) (io.ReadCloser, error) {

 	title := fmt.Sprintf("lcowdriver: diff: %s", id)

 	// Get VHDX info
 	ld, err := getLayerDetails(d.dir(id))

 	if err != nil {

 		logrus.Debugf("%s: failed to get vhdx information of %s: %s", title, d.dir(id), err)
 		return nil, err

 	}
 

 	// Start the SVM with a mapped virtual disk. Note that if the SVM is

 	// already running and we are in global mode, this will be

 	// hot-added.

 	mvd := hcsshim.MappedVirtualDisk{
 		HostPath:          ld.filename,
 		ContainerPath:     hostToGuest(ld.filename),

 		CreateInUtilityVM: true,
 		ReadOnly:          true,
 	}
 
 	logrus.Debugf("%s: starting service VM", title)

 	svm, err := d.startServiceVMIfNotRunning(id, []hcsshim.MappedVirtualDisk{mvd}, fmt.Sprintf("diff %s", id))

 	if err != nil {
 		return nil, err
 	}
 

 	logrus.Debugf("lcowdriver: diff: waiting for svm to finish booting")
 	err = svm.getStartError()
 	if err != nil {

 		d.terminateServiceVM(id, fmt.Sprintf("diff %s", id), false)

 		return nil, fmt.Errorf("lcowdriver: diff: svm failed to boot: %s", err)

 	}
 
 	// Obtain the tar stream for it

 	logrus.Debugf("%s: %s %s, size %d, ReadOnly %t", title, ld.filename, mvd.ContainerPath, ld.size, ld.isSandbox)
 	tarReadCloser, err := svm.config.VhdToTar(mvd.HostPath, mvd.ContainerPath, ld.isSandbox, ld.size)

 	if err != nil {

 		svm.hotRemoveVHDs(mvd)

 		d.terminateServiceVM(id, fmt.Sprintf("diff %s", id), false)

 		return nil, fmt.Errorf("%s failed to export layer to tar stream for id: %s, parent: %s : %s", title, id, parent, err)
 	}

 	logrus.Debugf("%s id %s parent %s completed successfully", title, id, parent)

 
 	// In safe/non-global mode, we can't tear down the service VM until things have been read.

 	return ioutils.NewReadCloserWrapper(tarReadCloser, func() error {
 		tarReadCloser.Close()
 		svm.hotRemoveVHDs(mvd)
 		d.terminateServiceVM(id, fmt.Sprintf("diff %s", id), false)
 		return nil
 	}), nil

 }
 
 // ApplyDiff extracts the changeset from the given diff into the
 // layer with the specified id and parent, returning the size of the
 // new layer in bytes. The layer should not be mounted when calling
 // this function. Another way of describing this is that ApplyDiff writes
 // to a new layer (a VHD in LCOW) the contents of a tarstream it's given.
 func (d *Driver) ApplyDiff(id, parent string, diff io.Reader) (int64, error) {
 	logrus.Debugf("lcowdriver: applydiff: id %s", id)
 

 	svm, err := d.startServiceVMIfNotRunning(id, nil, fmt.Sprintf("applydiff %s", id))
 	if err != nil {

 		return 0, err
 	}

 	defer d.terminateServiceVM(id, fmt.Sprintf("applydiff %s", id), false)
 

 	logrus.Debugf("lcowdriver: applydiff: waiting for svm to finish booting")
 	err = svm.getStartError()
 	if err != nil {
 		return 0, fmt.Errorf("lcowdriver: applydiff: svm failed to boot: %s", err)
 	}
 

 	// TODO @jhowardmsft - the retries are temporary to overcome platform reliablity issues.
 	// Obviously this will be removed as platform bugs are fixed.
 	retries := 0
 	for {
 		retries++
 		size, err := svm.config.TarToVhd(filepath.Join(d.dataRoot, id, layerFilename), diff)
 		if err != nil {
 			if retries <= 10 {
 				continue
 			}
 			return 0, err
 		}
 		return size, err
 	}

 }
 
 // Changes produces a list of changes between the specified layer
 // and its parent layer. If parent is "", then all changes will be ADD changes.
 // The layer should not be mounted when calling this function.
 func (d *Driver) Changes(id, parent string) ([]archive.Change, error) {
 	logrus.Debugf("lcowdriver: changes: id %s parent %s", id, parent)
 	// TODO @gupta-ak. Needs implementation with assistance from service VM
 	return nil, nil
 }
 
 // DiffSize calculates the changes between the specified layer
 // and its parent and returns the size in bytes of the changes
 // relative to its base filesystem directory.
 func (d *Driver) DiffSize(id, parent string) (size int64, err error) {
 	logrus.Debugf("lcowdriver: diffsize: id %s", id)
 	// TODO @gupta-ak. Needs implementation with assistance from service VM
 	return 0, nil
 }
 
 // GetMetadata returns custom driver information.
 func (d *Driver) GetMetadata(id string) (map[string]string, error) {
 	logrus.Debugf("lcowdriver: getmetadata: id %s", id)
 	m := make(map[string]string)
 	m["dir"] = d.dir(id)
 	return m, nil
 }
 

 // GetLayerPath gets the layer path on host (path to VHD/VHDX)
 func (d *Driver) GetLayerPath(id string) (string, error) {
 	return d.dir(id), nil
 }
 

 // dir returns the absolute path to the layer.
 func (d *Driver) dir(id string) string {

 	return filepath.Join(d.dataRoot, filepath.Base(id))

 }
 
 // getLayerChain returns the layer chain information.
 func (d *Driver) getLayerChain(id string) ([]string, error) {
 	jPath := filepath.Join(d.dir(id), "layerchain.json")
 	logrus.Debugf("lcowdriver: getlayerchain: id %s json %s", id, jPath)
 	content, err := ioutil.ReadFile(jPath)
 	if os.IsNotExist(err) {
 		return nil, nil
 	} else if err != nil {
 		return nil, fmt.Errorf("lcowdriver: getlayerchain: %s unable to read layerchain file %s: %s", id, jPath, err)
 	}
 
 	var layerChain []string
 	err = json.Unmarshal(content, &layerChain)
 	if err != nil {
 		return nil, fmt.Errorf("lcowdriver: getlayerchain: %s failed to unmarshall layerchain file %s: %s", id, jPath, err)
 	}
 	return layerChain, nil
 }
 
 // setLayerChain stores the layer chain information on disk.
 func (d *Driver) setLayerChain(id string, chain []string) error {
 	content, err := json.Marshal(&chain)
 	if err != nil {
 		return fmt.Errorf("lcowdriver: setlayerchain: %s failed to marshall layerchain json: %s", id, err)
 	}
 
 	jPath := filepath.Join(d.dir(id), "layerchain.json")
 	logrus.Debugf("lcowdriver: setlayerchain: id %s json %s", id, jPath)
 	err = ioutil.WriteFile(jPath, content, 0600)
 	if err != nil {
 		return fmt.Errorf("lcowdriver: setlayerchain: %s failed to write layerchain file: %s", id, err)
 	}
 	return nil
 }

 
 // getLayerDetails is a utility for getting a file name, size and indication of
 // sandbox for a VHD(x) in a folder. A read-only layer will be layer.vhd. A
 // read-write layer will be sandbox.vhdx.

 func getLayerDetails(folder string) (*layerDetails, error) {

 	var fileInfo os.FileInfo

 	ld := &layerDetails{
 		isSandbox: false,
 		filename:  filepath.Join(folder, layerFilename),
 	}
 
 	fileInfo, err := os.Stat(ld.filename)
 	if err != nil {
 		ld.filename = filepath.Join(folder, sandboxFilename)
 		if fileInfo, err = os.Stat(ld.filename); err != nil {
 			return nil, fmt.Errorf("failed to locate layer or sandbox in %s", folder)

 		}

 		ld.isSandbox = true

 	}

 	ld.size = fileInfo.Size()
 
 	return ld, nil

 }

 
 func (d *Driver) getAllMounts(id string) ([]hcsshim.MappedVirtualDisk, error) {
 	layerChain, err := d.getLayerChain(id)
 	if err != nil {
 		return nil, err
 	}
 	layerChain = append([]string{d.dir(id)}, layerChain...)
 
 	logrus.Debugf("getting all  layers: %v", layerChain)
 	disks := make([]hcsshim.MappedVirtualDisk, len(layerChain), len(layerChain))
 	for i := range layerChain {
 		ld, err := getLayerDetails(layerChain[i])
 		if err != nil {
 			logrus.Debugf("Failed to get LayerVhdDetails from %s: %s", layerChain[i], err)
 			return nil, err
 		}
 		disks[i].HostPath = ld.filename
 		disks[i].ContainerPath = hostToGuest(ld.filename)
 		disks[i].CreateInUtilityVM = true
 		disks[i].ReadOnly = !ld.isSandbox
 	}
 	return disks, nil
 }
 
 func hostToGuest(hostpath string) string {
 	return fmt.Sprintf("/tmp/%s", filepath.Base(filepath.Dir(hostpath)))
 }
 
 func unionMountName(disks []hcsshim.MappedVirtualDisk) string {
 	return fmt.Sprintf("%s-mount", disks[0].ContainerPath)
 }