disk: Round up disk size to 512 bytes

Apple virtualization framework rejects disks if the disk size is not
aligned to 512 bytes. QEMU block layer round the size up when creating
or resizing disks. Let's do the same to ensure that we don't create or
resize disk to unusable size.

I added only trivial tests fro the RoundUp helper since this kind of
code is easy to get wrong. We need to add more tests for creating and
resizing disk images.

Fixes #3390

Signed-off-by: Nir Soffer <[email protected]>

Author: nirs

pkg/nativeimgutil/nativeimgutil.go

@@ -23,6 +23,17 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// Disk image size must be aigned to sector size. Qemu block layer is rounding
+// up the size to 512 bytes. Apple virtualization framework reject disks not
+// aligned to 512 bytes.
+const sectorSize = 512
+
+// RoundUp rounds size up to sectorSize.
+func RoundUp(size int) int {
+	sectors := (size + sectorSize - 1) / sectorSize
+	return sectors * sectorSize
+}
+
 // CreateRawDataDisk creates an empty raw data disk.
 func CreateRawDataDisk(dir string, size int) error {
 	dataDisk := filepath.Join(dir, filenames.DataDisk)
@@ -34,13 +45,15 @@ func CreateRawDataDisk(dir string, size int) error {
 		return err
 	}
 	defer f.Close()
-	return f.Truncate(int64(size))
+	roundedSize := RoundUp(size)
+	return f.Truncate(int64(roundedSize))
 }
 
 // ResizeRawDataDisk resizes a raw data disk.
 func ResizeRawDataDisk(dir string, size int) error {
 	dataDisk := filepath.Join(dir, filenames.DataDisk)
-	return os.Truncate(dataDisk, int64(size))
+	roundedSize := RoundUp(size)
+	return os.Truncate(dataDisk, int64(roundedSize))
 }
 
 // ConvertToRaw converts a source disk into a raw disk.

pkg/nativeimgutil/nativeimgutil_test.go

@@ -13,6 +13,24 @@ import (
 	"gotest.tools/v3/assert"
 )
 
+func TestRoundUp(t *testing.T) {
+	tests := []struct {
+		Size    int
+		Rounded int
+	}{
+		{0, 0},
+		{1, 512},
+		{511, 512},
+		{512, 512},
+		{123456789, 123457024},
+	}
+	for _, tc := range tests {
+		if RoundUp(tc.Size) != tc.Rounded {
+			t.Errorf("expected %d, got %d", tc.Rounded, tc.Size)
+		}
+	}
+}
+
 func createImg(name, format, size string) error {
 	return exec.Command("qemu-img", "create", name, "-f", format, size).Run()
 }