vss: Add "timeout" option

Changing multiple "callAsyncFunctionAndWait" with fixed timeout
to calculated timeout based on deadline.

internal/fs/fs_local_vss.go

@@ -6,6 +6,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/options"
@@ -13,6 +14,7 @@ import (
 
 // VSSConfig holds extended options of windows volume shadow copy service.
 type VSSConfig struct {
+	Timeout time.Duration `option:"timeout" help:"time that the VSS can spend creating snapshots before timing out"`
 }
 
 func init() {
@@ -23,7 +25,9 @@ func init() {
 
 // NewVSSConfig returns a new VSSConfig with the default values filled in.
 func NewVSSConfig() VSSConfig {
-	return VSSConfig{}
+	return VSSConfig{
+		Timeout: time.Second * 120,
+	}
 }
 
 // ParseVSSConfig parses a VSS extended options to VSSConfig struct.
@@ -52,6 +56,7 @@ type LocalVss struct {
 	mutex           sync.RWMutex
 	msgError        ErrorHandler
 	msgMessage      MessageHandler
+	timeout         time.Duration
 }
 
 // statically ensure that LocalVss implements FS.
@@ -66,6 +71,7 @@ func NewLocalVss(msgError ErrorHandler, msgMessage MessageHandler, cfg VSSConfig
 		failedSnapshots: make(map[string]struct{}),
 		msgError:        msgError,
 		msgMessage:      msgMessage,
+		timeout:         cfg.Timeout,
 	}
 }
 
@@ -144,7 +150,7 @@ func (fs *LocalVss) snapshotPath(path string) string {
 			vssVolume := volumeNameLower + string(filepath.Separator)
 			fs.msgMessage("creating VSS snapshot for [%s]\n", vssVolume)
 
-			if snapshot, err := NewVssSnapshot(vssVolume, 120, fs.msgError); err != nil {
+			if snapshot, err := NewVssSnapshot(vssVolume, fs.timeout, fs.msgError); err != nil {
 				_ = fs.msgError(vssVolume, errors.Errorf("failed to create snapshot for [%s]: %s",
 					vssVolume, err))
 				fs.failedSnapshots[volumeNameLower] = struct{}{}

internal/fs/vss.go

@@ -4,6 +4,8 @@
 package fs
 
 import (
+	"time"
+
 	"github.com/restic/restic/internal/errors"
 )
 
@@ -34,7 +36,7 @@ func HasSufficientPrivilegesForVSS() error {
 // NewVssSnapshot creates a new vss snapshot. If creating the snapshots doesn't
 // finish within the timeout an error is returned.
 func NewVssSnapshot(
-	_ string, _ uint, _ ErrorHandler) (VssSnapshot, error) {
+	_ string, _ time.Duration, _ ErrorHandler) (VssSnapshot, error) {
 	return VssSnapshot{}, errors.New("VSS snapshots are only supported on windows")
 }
 

internal/fs/vss_windows.go

@@ -9,6 +9,7 @@ import (
 	"runtime"
 	"strings"
 	"syscall"
+	"time"
 	"unsafe"
 
 	ole "github.com/go-ole/go-ole"
@@ -617,8 +618,13 @@ func (vssAsync *IVSSAsync) QueryStatus() (HRESULT, uint32) {
 
 // WaitUntilAsyncFinished waits until either the async call is finished or
 // the given timeout is reached.
-func (vssAsync *IVSSAsync) WaitUntilAsyncFinished(millis uint32) error {
-	hresult := vssAsync.Wait(millis)
+func (vssAsync *IVSSAsync) WaitUntilAsyncFinished(timeout time.Duration) error {
+	const maxTimeout = 2147483647 * time.Millisecond
+	if timeout > maxTimeout {
+		timeout = maxTimeout
+	}
+
+	hresult := vssAsync.Wait(uint32(timeout.Milliseconds()))
 	err := newVssErrorIfResultNotOK("Wait() failed", hresult)
 	if err != nil {
 		vssAsync.Cancel()
@@ -677,7 +683,7 @@ type VssSnapshot struct {
 	snapshotProperties   VssSnapshotProperties
 	snapshotDeviceObject string
 	mountPointInfo       map[string]MountPoint
-	timeoutInMillis      uint32
+	timeout              time.Duration
 }
 
 // GetSnapshotDeviceObject returns root path to access the snapshot files
@@ -730,7 +736,7 @@ func HasSufficientPrivilegesForVSS() error {
 // NewVssSnapshot creates a new vss snapshot. If creating the snapshots doesn't
 // finish within the timeout an error is returned.
 func NewVssSnapshot(
-	volume string, timeoutInSeconds uint, msgError ErrorHandler) (VssSnapshot, error) {
+	volume string, timeout time.Duration, msgError ErrorHandler) (VssSnapshot, error) {
 	is64Bit, err := isRunningOn64BitWindows()
 
 	if err != nil {
@@ -744,7 +750,7 @@ func NewVssSnapshot(
 			runtime.GOARCH))
 	}
 
-	timeoutInMillis := uint32(timeoutInSeconds * 1000)
+	deadline := time.Now().Add(timeout)
 
 	oleIUnknown, err := initializeVssCOMInterface()
 	if oleIUnknown != nil {
@@ -796,7 +802,7 @@ func NewVssSnapshot(
 	}
 
 	err = callAsyncFunctionAndWait(iVssBackupComponents.GatherWriterMetadata,
-		"GatherWriterMetadata", timeoutInMillis)
+		"GatherWriterMetadata", deadline)
 	if err != nil {
 		iVssBackupComponents.Release()
 		return VssSnapshot{}, err
@@ -854,7 +860,7 @@ func NewVssSnapshot(
 	}
 
 	err = callAsyncFunctionAndWait(iVssBackupComponents.PrepareForBackup, "PrepareForBackup",
-		timeoutInMillis)
+		deadline)
 	if err != nil {
 		// After calling PrepareForBackup one needs to call AbortBackup() before releasing the VSS
 		// instance for proper cleanup.
@@ -865,7 +871,7 @@ func NewVssSnapshot(
 	}
 
 	err = callAsyncFunctionAndWait(iVssBackupComponents.DoSnapshotSet, "DoSnapshotSet",
-		timeoutInMillis)
+		deadline)
 	if err != nil {
 		iVssBackupComponents.AbortBackup()
 		iVssBackupComponents.Release()
@@ -901,7 +907,7 @@ func NewVssSnapshot(
 	}
 
 	return VssSnapshot{iVssBackupComponents, snapshotSetID, snapshotProperties,
-		snapshotProperties.GetSnapshotDeviceObject(), mountPointInfo, timeoutInMillis}, nil
+		snapshotProperties.GetSnapshotDeviceObject(), mountPointInfo, time.Until(deadline)}, nil
 }
 
 // Delete deletes the created snapshot.
@@ -922,8 +928,10 @@ func (p *VssSnapshot) Delete() error {
 	if p.iVssBackupComponents != nil {
 		defer p.iVssBackupComponents.Release()
 
+		deadline := time.Now().Add(p.timeout)
+
 		err = callAsyncFunctionAndWait(p.iVssBackupComponents.BackupComplete, "BackupComplete",
-			p.timeoutInMillis)
+			deadline)
 		if err != nil {
 			return err
 		}
@@ -945,7 +953,7 @@ type asyncCallFunc func() (*IVSSAsync, error)
 
 // callAsyncFunctionAndWait calls an async functions and waits for it to either
 // finish or timeout.
-func callAsyncFunctionAndWait(function asyncCallFunc, name string, timeoutInMillis uint32) error {
+func callAsyncFunctionAndWait(function asyncCallFunc, name string, deadline time.Time) error {
 	iVssAsync, err := function()
 	if err != nil {
 		return err
@@ -955,7 +963,12 @@ func callAsyncFunctionAndWait(function asyncCallFunc, name string, timeoutInMill
 		return newVssTextError(fmt.Sprintf("%s() returned nil", name))
 	}
 
-	err = iVssAsync.WaitUntilAsyncFinished(timeoutInMillis)
+	timeout := time.Until(deadline)
+	if timeout <= 0 {
+		return newVssTextError(fmt.Sprintf("%s() deadline exceeded", name))
+	}
+
+	err = iVssAsync.WaitUntilAsyncFinished(timeout)
 	iVssAsync.Release()
 	return err
 }