rbd: add additional space for encrypted volumes

issue: when a block-mode pvc is created with encryption enabled
there is some space reserved for the encryption metadata.
Which doesn't allows users to write extact amount of data that
they have requested for.

solution: create pvc with extra space needed for the encryption
metadata. `GetLuksHeaderSize()` function returns the luks2
encryption metadata(header size).

Signed-off-by: Praveen M <m.praveen@ibm.com>

internal/rbd/controllerserver.go

@@ -1217,6 +1217,11 @@ func (cs *ControllerServer) CreateSnapshot(
 		return nil, status.Error(codes.Internal, err.Error())
 	}
 
+	// remove the extra size of the LUKS header, if the volume is block encrypted.
+	if vol.isBlockEncrypted() {
+		vol.VolSize -= int64(util.GetLuksHeaderSize())
+	}
+
 	return &csi.CreateSnapshotResponse{
 		Snapshot: &csi.Snapshot{
 			SizeBytes:      vol.VolSize,

internal/rbd/rbd_util.go

@@ -443,8 +443,14 @@ func createImage(ctx context.Context, pOpts *rbdVolume, cr *util.Credentials) er
 		return fmt.Errorf("failed to get IOContext: %w", err)
 	}
 
-	err = librbd.CreateImage(pOpts.ioctx, pOpts.RbdImageName,
-		uint64(util.RoundOffVolSize(pOpts.VolSize)*helpers.MiB), options)
+	size := uint64(util.RoundOffVolSize(pOpts.VolSize) * helpers.MiB)
+
+	// add the extra size of the LUKS header to the image size if block encryption is enabled.
+	if pOpts.isBlockEncrypted() {
+		size += util.GetLuksHeaderSize()
+	}
+
+	err = librbd.CreateImage(pOpts.ioctx, pOpts.RbdImageName, size, options)
 	if err != nil {
 		return fmt.Errorf("failed to create rbd image: %w", err)
 	}
@@ -1598,6 +1604,11 @@ func (ri *rbdImage) getImageInfo() error {
 	// TODO: can rv.VolSize not be a uint64? Or initialize it to -1?
 	ri.VolSize = int64(imageInfo.Size)
 
+	// remove the extra size of the LUKS header, if the volume is block encrypted.
+	if ri.isBlockEncrypted() {
+		ri.VolSize -= int64(util.GetLuksHeaderSize())
+	}
+
 	features, err := image.GetFeatures()
 	if err != nil {
 		return err
@@ -1846,7 +1857,14 @@ func (ri *rbdImage) resize(newSize int64) error {
 	}
 	defer image.Close()
 
-	err = image.Resize(uint64(util.RoundOffVolSize(newSize) * helpers.MiB))
+	size := uint64(util.RoundOffVolSize(newSize) * helpers.MiB)
+
+	// add the extra size of the LUKS header to the image size if block encryption is enabled.
+	if ri.isBlockEncrypted() {
+		size += util.GetLuksHeaderSize()
+	}
+
+	err = image.Resize(size)
 	if err != nil {
 		return err
 	}

internal/util/cryptsetup.go

@@ -22,10 +22,22 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
+
+	"k8s.io/cloud-provider/volume/helpers"
 )
 
 // Limit memory used by Argon2i PBKDF to 32 MiB.
-const cryptsetupPBKDFMemoryLimit = 32 << 10 // 32768 KiB
+const (
+	cryptsetupPBKDFMemoryLimit = 32 << 10 // 32768 KiB
+	luks2MetadataSize          = 32 << 7  // 4096 KiB
+	luks2KeySlotsSize          = 32 << 8  // 8192 KiB
+)
+
+func GetLuksHeaderSize() uint64 {
+	size := uint64((((2 * luks2MetadataSize) + luks2KeySlotsSize) * helpers.KiB))
+
+	return size
+}
 
 // LuksFormat sets up volume as an encrypted LUKS partition.
 func LuksFormat(devicePath, passphrase string) (string, string, error) {
@@ -37,6 +49,10 @@ func LuksFormat(devicePath, passphrase string) (string, string, error) {
 		"luks2",
 		"--hash",
 		"sha256",
+		"--luks2-metadata-size",
+		strconv.Itoa(luks2MetadataSize)+"k",
+		"--luks2-keyslots-size",
+		strconv.Itoa(luks2KeySlotsSize)+"k",
 		"--pbkdf-memory",
 		strconv.Itoa(cryptsetupPBKDFMemoryLimit),
 		devicePath,