[bnb] Fix bnb skip modules (#24043)

* fix skip modules test

* oops

* address comments

src/transformers/utils/bitsandbytes.py

@@ -109,16 +109,18 @@ class `Int8Params` from `bitsandbytes`.
             module._parameters[tensor_name] = new_value
 
 
-def _replace_with_bnb_linear(model, modules_to_not_convert=None, current_key_name=None, quantization_config=None):
+def _replace_with_bnb_linear(
+    model, modules_to_not_convert=None, current_key_name=None, quantization_config=None, has_been_replaced=False
+):
     """
     Private method that wraps the recursion for module replacement.
 
     Returns the converted model and a boolean that indicates if the conversion has been successfull or not.
     """
-    has_been_replaced = False
     for name, module in model.named_children():
         if current_key_name is None:
             current_key_name = []
+        current_key_name.append(name)
 
         if isinstance(module, nn.Linear) and name not in modules_to_not_convert:
             # Check if the current key is not in the `modules_to_not_convert`
@@ -151,14 +153,16 @@ def _replace_with_bnb_linear(model, modules_to_not_convert=None, current_key_nam
                             has_been_replaced = True
                     # Force requires grad to False to avoid unexpected errors
                     model._modules[name].requires_grad_(False)
-        # Remove the last key for recursion
         if len(list(module.children())) > 0:
             _, has_been_replaced = _replace_with_bnb_linear(
                 module,
                 modules_to_not_convert,
                 current_key_name,
                 quantization_config,
+                has_been_replaced=has_been_replaced,
             )
+        # Remove the last key for recursion
+        current_key_name.pop(-1)
     return model, has_been_replaced
 
 

tests/bitsandbytes/test_mixed_int8.py

@@ -146,6 +146,26 @@ def test_linear_are_8bit(self):
                 if name not in ["lm_head"] + T5PreTrainedModel._keep_in_fp32_modules:
                     self.assertTrue(module.weight.dtype == torch.int8)
 
+    def test_llm_skip(self):
+        r"""
+        A simple test to check if `llm_int8_skip_modules` works as expected
+        """
+        import bitsandbytes as bnb
+
+        quantization_config = BitsAndBytesConfig(load_in_8bit=True, llm_int8_skip_modules=["classifier"])
+        seq_classification_model = AutoModelForSequenceClassification.from_pretrained(
+            "roberta-large-mnli", quantization_config=quantization_config
+        )
+        self.assertTrue(seq_classification_model.roberta.encoder.layer[0].output.dense.weight.dtype == torch.int8)
+        self.assertTrue(
+            isinstance(seq_classification_model.roberta.encoder.layer[0].output.dense, bnb.nn.Linear8bitLt)
+        )
+
+        self.assertTrue(isinstance(seq_classification_model.classifier.dense, nn.Linear))
+        self.assertTrue(seq_classification_model.classifier.dense.weight.dtype != torch.int8)
+        self.assertTrue(isinstance(seq_classification_model.classifier.out_proj, nn.Linear))
+        self.assertTrue(seq_classification_model.classifier.out_proj != torch.int8)
+
     def test_generate_quality(self):
         r"""
         Test the generation quality of the quantized model and see that we are matching the expected output.