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

@@ -1627,6 +1627,10 @@ func (cs *ControllerServer) ControllerExpandVolume(
 		}
 	}
 
+	if rbdVol.isBlockEncrypted() {
+		rbdVol.VolSize -= util.GetLuksHeaderSize()
+	}
+
 	return &csi.ControllerExpandVolumeResponse{
 		CapacityBytes:         rbdVol.VolSize,
 		NodeExpansionRequired: nodeExpansion,

internal/rbd/rbd_util.go

@@ -443,8 +443,12 @@ 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)
+	if pOpts.isBlockEncrypted() {
+		size += uint64(util.GetLuksHeaderSize())
+	}
+
+	err = librbd.CreateImage(pOpts.ioctx, pOpts.RbdImageName, size, options)
 	if err != nil {
 		return fmt.Errorf("failed to create rbd image: %w", err)
 	}
@@ -1846,7 +1850,12 @@ 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)
+	if ri.isBlockEncrypted() {
+		size += uint64(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() int64 {
+	size := int64((((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,