disk: add function for resizing Entities based on dirs

New function that ensures that a partition can hold the total sum of all
the required sizes of specific directories on the partition.  The
function sums the required directory sizes grouped by their mountpoint
and then resizes the entity path of that Mountable.

internal/disk/disk_test.go

@@ -573,3 +573,113 @@ func TestFindDirectoryPartition(t *testing.T) {
 		assert.Nil(pt.findDirectoryEntityPath("/var"))
 	}
 }
+
+func TestEnsureDirectorySizes(t *testing.T) {
+	assert := assert.New(t)
+
+	GiB := 1024 * 1024 * 1024
+	varSizes := map[string]uint64{
+		"/var/lib":         uint64(3 * GiB),
+		"/var/cache":       uint64(2 * GiB),
+		"/var/log/journal": uint64(2 * GiB),
+	}
+
+	varAndHomeSizes := map[string]uint64{
+		"/var/lib":         uint64(3 * GiB),
+		"/var/cache":       uint64(2 * GiB),
+		"/var/log/journal": uint64(2 * GiB),
+		"/home/user/data":  uint64(10 * GiB),
+	}
+
+	{
+		pt := testPartitionTables["plain"]
+		pt = *pt.Clone().(*PartitionTable) // don't modify the original test data
+
+		{
+			// make sure we have the correct volume
+			// guard against changes in the test pt
+			rootPart := pt.Partitions[3]
+			rootPayload := rootPart.Payload.(*Filesystem)
+
+			assert.Equal("/", rootPayload.Mountpoint)
+			assert.Equal(uint64(0), rootPart.Size)
+		}
+
+		{
+			// add requirements for /var subdirs that are > 5 GiB
+			pt.EnsureDirectorySizes(varSizes)
+			rootPart := pt.Partitions[3]
+			assert.Equal(uint64(7*GiB), rootPart.Size)
+
+			// invalid
+			assert.Panics(func() { pt.EnsureDirectorySizes(map[string]uint64{"invalid": uint64(300)}) })
+		}
+	}
+
+	{
+		pt := testPartitionTables["luks+lvm"]
+		pt = *pt.Clone().(*PartitionTable) // don't modify the original test data
+
+		{
+			// make sure we have the correct volume
+			// guard against changes in the test pt
+			rootPart := pt.Partitions[3]
+			rootLUKS := rootPart.Payload.(*LUKSContainer)
+			rootVG := rootLUKS.Payload.(*LVMVolumeGroup)
+			rootLV := rootVG.LogicalVolumes[0]
+			rootFS := rootLV.Payload.(*Filesystem)
+			homeLV := rootVG.LogicalVolumes[1]
+			homeFS := homeLV.Payload.(*Filesystem)
+
+			assert.Equal(uint64(5*GiB), rootPart.Size)
+			assert.Equal("/", rootFS.Mountpoint)
+			assert.Equal(uint64(2*GiB), rootLV.Size)
+			assert.Equal("/home", homeFS.Mountpoint)
+			assert.Equal(uint64(2*GiB), homeLV.Size)
+		}
+
+		{
+			// add requirements for /var subdirs that are > 5 GiB
+			pt.EnsureDirectorySizes(varAndHomeSizes)
+			rootPart := pt.Partitions[3]
+			rootLUKS := rootPart.Payload.(*LUKSContainer)
+			rootVG := rootLUKS.Payload.(*LVMVolumeGroup)
+			rootLV := rootVG.LogicalVolumes[0]
+			homeLV := rootVG.LogicalVolumes[1]
+			assert.Equal(uint64(17*GiB)+rootVG.MetadataSize(), rootPart.Size)
+			assert.Equal(uint64(7*GiB), rootLV.Size)
+			assert.Equal(uint64(10*GiB), homeLV.Size)
+
+			// invalid
+			assert.Panics(func() { pt.EnsureDirectorySizes(map[string]uint64{"invalid": uint64(300)}) })
+		}
+	}
+
+	{
+		pt := testPartitionTables["btrfs"]
+		pt = *pt.Clone().(*PartitionTable) // don't modify the original test data
+
+		{
+			// make sure we have the correct volume
+			// guard against changes in the test pt
+			rootPart := pt.Partitions[3]
+			rootPayload := rootPart.Payload.(*Btrfs)
+			assert.Equal("/", rootPayload.Subvolumes[0].Mountpoint)
+			assert.Equal(uint64(0), rootPayload.Subvolumes[0].Size)
+			assert.Equal("/var", rootPayload.Subvolumes[1].Mountpoint)
+			assert.Equal(uint64(5*GiB), rootPayload.Subvolumes[1].Size)
+		}
+
+		{
+			// add requirements for /var subdirs that are > 5 GiB
+			pt.EnsureDirectorySizes(varSizes)
+			rootPart := pt.Partitions[3]
+			rootPayload := rootPart.Payload.(*Btrfs)
+			assert.Equal(uint64(7*GiB), rootPayload.Subvolumes[1].Size)
+
+			// invalid
+			assert.Panics(func() { pt.EnsureDirectorySizes(map[string]uint64{"invalid": uint64(300)}) })
+		}
+	}
+
+}