[tmp] Always report 4 MiB block size because Lustre statfs suddenly r…

…eturns 4K instead of 4M maybe because of lazystatfs mount option and a dead OST

ratarmount.py

@@ -858,6 +858,12 @@ def fsync(self, path, datasync, fh):
 
     @overrides(fuse.Operations)
     def statfs(self, path):
+        return {
+            'f_bsize': 4 * 1024 * 1024,
+            'f_frsize': 4 * 1024 * 1024,
+            'f_namemax': 255,
+        }
+
         # The filesystem block size is used, e.g., by Python as the default buffer size and therefore the
         # default (p)read size when possible. For network file systems such as Lustre, or block compression
         # such as in SquashFS, this proved to be highly insufficient to reach optimal performance!