Bug Fix: Fixed FileExistsError (#1187)

Summary:
Fixed bug where multiple workers try to write to the same folder that doesn't exist yet, it causes a FileExistsError because a different work already created the directory structure.

Fixes #{1186}

### Changes

- Removed if statement which checks if `dirname` exists and modified to use built-in `os.makedirs` feature for checking if `dirname` exists

Pull Request resolved: #1187

Reviewed By: ejguan

Differential Revision: D55278447

Pulled By: gokulavasan

fbshipit-source-id: 50088457cce3d0b5c62529b5290d45f31ce0144f

torchdata/datapipes/iter/util/cacheholder.py

@@ -258,8 +258,7 @@ def _cache_check_fn(data, filepath_fn, hash_dict, hash_type, extra_check_fn, cac
         if not cached_file_exists:
             promise_filepath = _promise_filename(filepath, cache_uuid)
             dirname = os.path.dirname(promise_filepath)
-            if not os.path.exists(dirname):
-                os.makedirs(dirname)
+            os.makedirs(dirname, exist_ok=True)
 
             with portalocker.Lock(promise_filepath, "a+", flags=portalocker.LockFlags.EXCLUSIVE) as promise_fh:
                 promise_fh.seek(0)