incusd/storage/lvm: Require 512-bytes physical block size for VM images

Closes #1375

Signed-off-by: Stéphane Graber <[email protected]>

internal/server/storage/drivers/driver_lvm_utils.go

@@ -9,6 +9,9 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
 
 	internalInstance "github.com/lxc/incus/v6/internal/instance"
 	"github.com/lxc/incus/v6/internal/linux"
@@ -879,3 +882,22 @@ func (d *lvm) deactivateVolume(vol Volume) (bool, error) {
 
 	return false, nil
 }
+
+func (d *lvm) getBlockSize(path string) (int, error) {
+	// Open the block device.
+	f, err := os.Open(path)
+	if err != nil {
+		return -1, err
+	}
+
+	defer func() { _ = f.Close() }()
+
+	// Query the physical block size.
+	var res int32
+	_, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(f.Fd()), unix.BLKPBSZGET, uintptr(unsafe.Pointer(&res)))
+	if errno != 0 {
+		return -1, fmt.Errorf("Failed to BLKPBSZGET: %w", unix.Errno(errno))
+	}
+
+	return int(res), nil
+}

internal/server/storage/drivers/driver_lvm_volumes.go

@@ -70,6 +70,18 @@ func (d *lvm) CreateVolume(vol Volume, filler *VolumeFiller, op *operations.Oper
 				if err != nil {
 					return err
 				}
+
+				// Check the block size for image volumes.
+				if vol.volType == VolumeTypeImage {
+					blockSize, err := d.getBlockSize(devPath)
+					if err != nil {
+						return err
+					}
+
+					if blockSize != 512 {
+						return fmt.Errorf("Underlying storage uses %d bytes sector size when virtual machine images require 512 bytes", blockSize)
+					}
+				}
 			}
 
 			allowUnsafeResize := false