disk: test relayout() function fix

Add two new test cases, dos and gpt with LVM, that force the VG
partition and partition table to grow to fit the LVs.  The partition
size calculation can be a bit hard to follow with metadata and rounding,
but the comments should help.

pkg/disk/partition_table_internal_test.go

@@ -478,7 +478,6 @@ func TestRelayout(t *testing.T) {
 									Payload: &Filesystem{
 										Mountpoint: "/",
 									},
-									// TODO: fix bug where the VG partition is not resized to fit the sum of LVs
 									Size: 10 * MiB,
 								},
 							},
@@ -691,6 +690,116 @@ func TestRelayout(t *testing.T) {
 				},
 			},
 		},
+		"lvm-dos-grow-rootvg": {
+			pt: &PartitionTable{
+				Type: "dos",
+				Size: 10 * MiB, // PT is smaller than the sum of Partitions
+				Partitions: []Partition{
+					{
+						Size: 200 * MiB,
+					},
+					{
+						Size: 10 * MiB, // VG partition is smaller than sum of LVs
+						Payload: &LVMVolumeGroup{
+							LogicalVolumes: []LVMLogicalVolume{
+								{
+									Size: 20 * MiB,
+								},
+								{
+									Payload: &Filesystem{
+										Mountpoint: "/",
+									},
+									Size: 100 * MiB,
+								},
+							},
+						},
+					},
+				},
+			},
+			size: 99 * MiB,
+			expected: &PartitionTable{
+				Type: "dos",
+				Size: 325 * MiB,
+				Partitions: []Partition{
+					{
+						Start: 1 * MiB, // 1 sector header aligned up to the default grain (1 MiB)
+						Size:  200 * MiB,
+					},
+					{
+						Start: 201 * MiB,
+						Size:  124 * MiB, // grows to fit logical volumes + 1 MiB metadata, rounded up to default extent size (4 MiB)
+						Payload: &LVMVolumeGroup{
+							LogicalVolumes: []LVMLogicalVolume{
+								{
+									Size: 20 * MiB,
+								},
+								{
+									Payload: &Filesystem{
+										Mountpoint: "/",
+									},
+									Size: 100 * MiB,
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		"lvm-gpt-grow-rootvg": {
+			pt: &PartitionTable{
+				Type: "gpt",
+				Size: 10 * MiB,
+				Partitions: []Partition{
+					{
+						Size: 200 * MiB,
+					},
+					{
+						Size: 10 * MiB,
+						Payload: &LVMVolumeGroup{
+							LogicalVolumes: []LVMLogicalVolume{
+								{
+									Size: 20 * MiB,
+								},
+								{
+									Payload: &Filesystem{
+										Mountpoint: "/",
+									},
+									Size: 100 * MiB,
+								},
+							},
+						},
+					},
+				},
+			},
+			size: 99 * MiB,
+			expected: &PartitionTable{
+				Type: "gpt",
+				Size: 326 * MiB,
+				Partitions: []Partition{
+					{
+						Start: 1 * MiB, // 1 sector header aligned up to the default grain (1 MiB)
+						Size:  200 * MiB,
+					},
+					{
+						Start: 201 * MiB,
+						Size:  125*MiB - (DefaultSectorSize + (128 * 128)), // grows to fit logical volumes and metadata, rounded up to default extent size + (1 MiB - footer) so that the no partitions shrink below the desired sizes
+						Payload: &LVMVolumeGroup{
+							LogicalVolumes: []LVMLogicalVolume{
+								{
+									Size: 20 * MiB,
+								},
+								{
+									Payload: &Filesystem{
+										Mountpoint: "/",
+									},
+									Size: 100 * MiB,
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for name := range testCases {