persist source dev size

Signed-off-by: Lyndon-Li <lyonghui@vmware.com>

pkg/uploader/block/snapshot.go

@@ -222,7 +222,17 @@ func Restore(ctx context.Context, blkUp Uploader, rep udmrepo.BackupRepo, snapsh
 
 	defer destDev.Close()
 
-	size, err := blkUp.Restore(snapshot, destInfo{dev: destDev, path: destPath}, bitmap.Iterator(), uploaderCfg)
+	destSize, err := destDev.Seek(0, io.SeekEnd)
+	if err != nil {
+		return 0, errors.Wrapf(err, "error getting length of block device %s", dest)
+	}
+
+	_, err = destDev.Seek(0, io.SeekStart)
+	if err != nil {
+		return 0, errors.Wrapf(err, "error reset pos of block device %s", dest)
+	}
+
+	size, err := blkUp.Restore(snapshot, destInfo{dev: destDev, path: destPath, size: destSize}, bitmap.Iterator(), uploaderCfg)
 	if err != nil {
 		return 0, errors.Wrapf(err, "error restoring to block dev %s", destPath)
 	}

pkg/uploader/block/uploader.go

@@ -21,6 +21,7 @@ import (
 	"io"
 	"os"
 	"runtime"
+	"strconv"
 	"strings"
 
 	"github.com/cockroachdb/errors"
@@ -35,8 +36,9 @@ import (
 var ErrCanceled = errors.New("uploader is canceled")
 
 const (
-	blockSize  = (1 << 20)
-	bufferSize = 100 << 20
+	blockSize         = (1 << 20)
+	bufferSize        = 100 << 20
+	bdevSourceSizeTag = "bdev-source-size"
 )
 
 type sourceInfo struct {
@@ -48,6 +50,7 @@ type sourceInfo struct {
 type destInfo struct {
 	dev  *os.File
 	path string
+	size int64
 }
 
 type Uploader interface {
@@ -134,6 +137,9 @@ func (blkup *blockUploader) Backup(source sourceInfo, parentObject udmrepo.ID, b
 			Type:        udmrepo.ObjectDataTypeMetadata,
 			Permissions: 0o777,
 		},
+		Tags: map[string]string{
+			bdevSourceSizeTag: strconv.FormatInt(source.size, 10),
+		},
 	}, backupSize, nil
 }