call fsync on saving

nvchecker/core.py

@@ -41,6 +41,9 @@ def safe_overwrite(fname, data, *, method='write', mode='w', encoding=None):
   # if not using "with", write can fail without exception
   with open(tmpname, mode, encoding=encoding) as f:
     getattr(f, method)(data)
+    # see also: https://thunk.org/tytso/blog/2009/03/15/dont-fear-the-fsync/
+    f.flush()
+    os.fsync(f.fileno())
   # if the above write failed (because disk is full etc), the old data should be kept
   os.rename(tmpname, fname)