Fix sized filesystem

If purging is enabled, overwriting a file with a file of the same
or smaller size will not result in an error.

It is now possible to change the purging mode on an existing sized
filesystem.

app/api/api.go

@@ -426,7 +426,7 @@ func (a *api) start() error {
 	} else {
 		a.memfs.SetMetadata("base", baseMemFS.String())
 		if sizedfs, ok := a.memfs.(fs.SizedFilesystem); ok {
-			sizedfs.Resize(cfg.Storage.Memory.Size * 1024 * 1024)
+			sizedfs.Resize(cfg.Storage.Memory.Size*1024*1024, cfg.Storage.Memory.Purge)
 		}
 	}
 

io/fs/readonly.go

@@ -49,6 +49,6 @@ func (r *readOnlyFilesystem) Purge(size int64) int64 {
 	return 0
 }
 
-func (r *readOnlyFilesystem) Resize(size int64) error {
+func (r *readOnlyFilesystem) Resize(size int64, purge bool) error {
 	return os.ErrPermission
 }

io/fs/readonly_test.go

@@ -45,6 +45,6 @@ func TestReadOnly(t *testing.T) {
 	ros, ok := ro.(SizedFilesystem)
 	require.True(t, ok, "must implement SizedFilesystem")
 
-	err = ros.Resize(100)
+	err = ros.Resize(100, false)
 	require.Error(t, err)
 }

io/fs/sized.go

@@ -10,7 +10,7 @@ type SizedFilesystem interface {
 	Filesystem
 
 	// Resize resizes the filesystem to the new size. Files may need to be deleted.
-	Resize(size int64) error
+	Resize(size int64, purge bool) error
 }
 
 type PurgeFilesystem interface {
@@ -48,7 +48,9 @@ func (r *sizedFilesystem) Size() (int64, int64) {
 	return currentSize, r.maxSize
 }
 
-func (r *sizedFilesystem) Resize(size int64) error {
+func (r *sizedFilesystem) Resize(size int64, purge bool) error {
+	r.purge = purge
+
 	currentSize, _ := r.Size()
 	if size >= currentSize {
 		// If the new size is the same or larger than the current size,
@@ -82,9 +84,15 @@ func (r *sizedFilesystem) WriteFileReader(path string, rd io.Reader) (int64, boo
 		return -1, false, fmt.Errorf("File is too big")
 	}
 
-	// Calculate the new size of the filesystem
 	newSize := currentSize + size
 
+	// Calculate the new size of the filesystem
+	finfo, err := r.Filesystem.Stat(path)
+	if err == nil {
+		// If the file already exist, take it's size into account
+		newSize -= finfo.Size()
+	}
+
 	// If the the new size is larger than the allowed size, we have to free
 	// some space.
 	if newSize > maxSize {
@@ -117,9 +125,15 @@ func (r *sizedFilesystem) WriteFileSafe(path string, data []byte) (int64, bool,
 		return -1, false, fmt.Errorf("File is too big")
 	}
 
-	// Calculate the new size of the filesystem
 	newSize := currentSize + size
 
+	// Calculate the new size of the filesystem
+	finfo, err := r.Filesystem.Stat(path)
+	if err == nil {
+		// If the file already exist, take it's size into account
+		newSize -= finfo.Size()
+	}
+
 	// If the the new size is larger than the allowed size, we have to free
 	// some space.
 	if newSize > maxSize {

io/fs/sized_test.go

@@ -35,7 +35,7 @@ func TestSizedResize(t *testing.T) {
 	require.Equal(t, int64(0), cur)
 	require.Equal(t, int64(10), max)
 
-	err := fs.Resize(20)
+	err := fs.Resize(20, false)
 	require.NoError(t, err)
 
 	cur, max = fs.Size()
@@ -44,6 +44,26 @@ func TestSizedResize(t *testing.T) {
 	require.Equal(t, int64(20), max)
 }
 
+func TestSizedResizeSetPurge(t *testing.T) {
+	fs, _ := NewSizedFilesystem(newMemFS(), 10, false)
+
+	_, _, err := fs.WriteFileReader("/foobar1", strings.NewReader("xxxxx"))
+	require.NoError(t, err)
+
+	_, _, err = fs.WriteFileReader("/foobar2", strings.NewReader("xxxxx"))
+	require.NoError(t, err)
+
+	_, _, err = fs.WriteFileReader("/foobar3", strings.NewReader("xxxxx"))
+	require.Error(t, err)
+
+	fs.Resize(10, true)
+
+	_, _, err = fs.WriteFileReader("/foobar3", strings.NewReader("xxxxx"))
+	require.NoError(t, err)
+
+	require.Equal(t, int64(2), fs.Files())
+}
+
 func TestSizedResizePurge(t *testing.T) {
 	fs, _ := NewSizedFilesystem(newMemFS(), 10, false)
 
@@ -59,7 +79,7 @@ func TestSizedResizePurge(t *testing.T) {
 	require.Equal(t, int64(10), cur)
 	require.Equal(t, int64(10), max)
 
-	err := fs.Resize(5)
+	err := fs.Resize(5, false)
 	require.NoError(t, err)
 
 	cur, max = fs.Size()
@@ -132,6 +152,31 @@ func TestSizedReplaceNoPurge(t *testing.T) {
 	cur = fs.Files()
 
 	require.Equal(t, int64(1), cur)
+
+	data = strings.NewReader("zzzzzzz")
+
+	size, created, err = fs.WriteFileReader("/foobar", data)
+
+	require.Nil(t, err)
+	require.Equal(t, int64(7), size)
+	require.Equal(t, false, created)
+
+	cur, max = fs.Size()
+
+	require.Equal(t, int64(7), cur)
+	require.Equal(t, int64(10), max)
+
+	cur = fs.Files()
+
+	require.Equal(t, int64(1), cur)
+
+	data = strings.NewReader("zzzzzzzz")
+
+	size, created, err = fs.WriteFileReader("/foobar", data)
+
+	require.Nil(t, err)
+	require.Equal(t, int64(8), size)
+	require.Equal(t, false, created)
 }
 
 func TestSizedReplacePurge(t *testing.T) {