diff --git a/powerline/lib/vcs/__init__.py b/powerline/lib/vcs/__init__.py
index 2bbc9bdf..aa53abf8 100644
--- a/powerline/lib/vcs/__init__.py
+++ b/powerline/lib/vcs/__init__.py
@@ -16,7 +16,7 @@ def generate_directories(path):
 	while True:
 		old_path = path
 		path = os.path.dirname(path)
-		if path == old_path:
+		if path == old_path or not path:
 			break
 		yield path
 
diff --git a/powerline/segments/vim.py b/powerline/segments/vim.py
index 06da9e5d..09b4c636 100644
--- a/powerline/segments/vim.py
+++ b/powerline/segments/vim.py
@@ -20,6 +20,7 @@ vim_funcs = {
 	'fnamemodify': vim_get_func('fnamemodify'),
 	'expand': vim_get_func('expand'),
 	'bufnr': vim_get_func('bufnr', rettype=int),
+	'line2byte': vim_get_func('line2byte', rettype=int),
 }
 
 vim_modes = {
@@ -195,10 +196,9 @@ def file_name(segment_info, display_no_file=False, no_file_text='[No file]'):
 	return file_name
 
 
-@requires_segment_info
-@memoize(2, cache_key=bufname, cache_reg_func=purgebuf_on_shell_and_write)
-def file_size(segment_info, suffix='B', si_prefix=False):
-	'''Return file size.
+@window_cached
+def file_size(suffix='B', si_prefix=False):
+	'''Return file size in &encoding.
 
 	:param str suffix:
 		string appended to the file size
@@ -206,13 +206,9 @@ def file_size(segment_info, suffix='B', si_prefix=False):
 		use SI prefix, e.g. MB instead of MiB
 	:return: file size or None if the file isn't saved or if the size is too big to fit in a number
 	'''
-	file_name = segment_info['buffer'].name
-	if not file_name:
-		return None
-	try:
-		file_size = os.stat(file_name).st_size
-	except:
-		return None
+	# Note: returns file size in &encoding, not in &fileencoding. But returned 
+	# size is updated immediately; and it is valid for any buffer
+	file_size = vim_funcs['line2byte'](len(vim.current.buffer) + 1) - 1
 	return humanize_bytes(file_size, suffix, si_prefix)
 
 
diff --git a/tests/test_segments.py b/tests/test_segments.py
index 491e4a3a..ec6be894 100644
--- a/tests/test_segments.py
+++ b/tests/test_segments.py
@@ -229,7 +229,7 @@ class TestVim(TestCase):
 
 	def test_file_size(self):
 		segment_info = vim_module._get_segment_info()
-		self.assertEqual(vim.file_size(segment_info=segment_info), None)
+		self.assertEqual(vim.file_size(segment_info=segment_info), '0 B')
 		with vim_module._with('buffer', os.path.join(os.path.dirname(__file__), 'empty')) as segment_info:
 			self.assertEqual(vim.file_size(segment_info=segment_info), '0 B')
 
diff --git a/tests/vim.py b/tests/vim.py
index 1b9b820c..08e57276 100644
--- a/tests/vim.py
+++ b/tests/vim.py
@@ -149,6 +149,12 @@ def _emul_exists(varname):
 		return varname[2:] in _g
 	raise NotImplementedError
 
+@_logged
+def _emul_line2byte(line):
+	buflines = _buf_lines[_buffer()]
+	if line == len(buflines) + 1:
+		return sum((len(s) for s in buflines)) + 1
+	raise NotImplementedError
 
 _window_ids = [None]
 _window_id = 0
@@ -242,6 +248,15 @@ class _Buffer(object):
 			_buf_scopes.pop(bufnr)
 
 
+class _Current(object):
+	@property
+	def buffer(self):
+		return buffers[_buffer()]
+
+
+current = _Current()
+
+
 _dict = None