Check custom volume size is a multiple of 512 bytes

libvirt/helper/suppress/volumes.go

@@ -0,0 +1,25 @@
+package suppress
+
+import (
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+	"strconv"
+)
+
+const qcow2SectorSize = 512
+
+// Suppress the diff if the specified volume size is qemu-img round up to sector size.
+func Qcow2SizeDiffSuppressFunc(_, oldSizeStr, newSizeStr string, k *schema.ResourceData) bool {
+	if format := k.Get("format"); format != "qcow2" {
+		return false
+	}
+
+	// On first apply these are nil strings, so there's always a diff.
+	if oldSizeStr == "" {
+		return false
+	}
+
+	oldSize, _ := strconv.ParseUint(oldSizeStr, 10, 64)
+	newSize, _ := strconv.ParseUint(newSizeStr, 10, 64)
+
+	return oldSize-newSize < qcow2SectorSize
+}

libvirt/resource_libvirt_volume.go

@@ -9,6 +9,8 @@ import (
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+
+	"github.com/dmacvicar/terraform-provider-libvirt/libvirt/helper/suppress"
 )
 
 func resourceLibvirtVolume() *schema.Resource {
@@ -38,6 +40,7 @@ func resourceLibvirtVolume() *schema.Resource {
 				Optional: true,
 				Computed: true,
 				ForceNew: true,
+				DiffSuppressFunc: suppress.Qcow2SizeDiffSuppressFunc,
 			},
 			"format": {
 				Type:     schema.TypeString,

libvirt/resource_libvirt_volume_test.go

@@ -125,6 +125,43 @@ func TestAccLibvirtVolume_Basic(t *testing.T) {
 	})
 }
 
+func TestAccLibvirtVolume_SizeRound(t *testing.T) {
+	var volume libvirt.StorageVol
+	randomVolumeResource := acctest.RandStringFromCharSet(10, acctest.CharSetAlpha)
+	randomVolumeName := acctest.RandStringFromCharSet(10, acctest.CharSetAlpha)
+	randomPoolName := acctest.RandStringFromCharSet(10, acctest.CharSetAlpha)
+	randomPoolPath := "/tmp/terraform-provider-libvirt-pool-" + randomPoolName
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckLibvirtVolumeDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: fmt.Sprintf(`
+                resource "libvirt_pool" "%s" {
+                    name = "%s"
+                    type = "dir"
+                    path = "%s"
+                }
+
+		resource "libvirt_volume" "%s" {
+		    name = "%s"
+		    size =  1073741823
+                    pool = "${libvirt_pool.%s.name}"
+				}`, randomPoolName, randomPoolName, randomPoolPath, randomVolumeResource, randomVolumeName, randomPoolName),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckLibvirtVolumeExists("libvirt_volume."+randomVolumeResource, &volume),
+					resource.TestCheckResourceAttr(
+						"libvirt_volume."+randomVolumeResource, "name", randomVolumeName),
+					resource.TestCheckResourceAttr(
+						"libvirt_volume."+randomVolumeResource, "size", "1073741824"),
+				),
+			},
+		},
+	})
+}
+
+
 func TestAccLibvirtVolume_BackingStoreTestByID(t *testing.T) {
 	var volume libvirt.StorageVol
 	random := acctest.RandStringFromCharSet(10, acctest.CharSetAlpha)