[core] Fix use_reentrant issues (#1036)

* fix use_reentrant issues

* fix

* fixup

* address comments.

* add warnings

* oops

* fix

* quality

src/peft/utils/other.py

@@ -63,18 +63,29 @@ def starcoder_model_postprocess_past_key_value(past_key_values):
     return tuple(result)
 
 
-def prepare_model_for_kbit_training(model, use_gradient_checkpointing=True):
+def prepare_model_for_kbit_training(model, use_gradient_checkpointing=True, gradient_checkpointing_kwargs=None):
     r"""
+    Note this method only works for `transformers` models.
+
     This method wraps the entire protocol for preparing a model before running a training. This includes:
         1- Cast the layernorm in fp32 2- making output embedding layer require grads 3- Add the upcasting of the lm
         head to fp32
 
     Args:
-        model, (`transformers.PreTrainedModel`):
+        model (`transformers.PreTrainedModel`):
             The loaded model from `transformers`
+        use_gradient_checkpointing (`bool`, *optional*, defaults to `True`):
+            If True, use gradient checkpointing to save memory at the expense of slower backward pass.
+        gradient_checkpointing_kwargs (`dict`, *optional*, defaults to `None`):
+            Keyword arguments to pass to the gradient checkpointing function, please refer to the documentation of
+            `torch.utils.checkpoint.checkpoint` for more details about the arguments that you can pass to that method.
+            Note this is only available in the latest transformers versions (> 4.34.1).
     """
     loaded_in_kbit = getattr(model, "is_loaded_in_8bit", False) or getattr(model, "is_loaded_in_4bit", False)
     is_gptq_quantized = getattr(model, "quantization_method", None) == "gptq"
+    if gradient_checkpointing_kwargs is None:
+        gradient_checkpointing_kwargs = {}
+
     for name, param in model.named_parameters():
         # freeze base model's layers
         param.requires_grad = False
@@ -86,19 +97,36 @@ def prepare_model_for_kbit_training(model, use_gradient_checkpointing=True):
                 param.data = param.data.to(torch.float32)
 
     if (loaded_in_kbit or is_gptq_quantized) and use_gradient_checkpointing:
-        # For backward compatibility
-        if hasattr(model, "enable_input_require_grads"):
-            model.enable_input_require_grads()
-        else:
+        # When having `use_reentrant=False` + gradient_checkpointing, there is no need for this hack
+        if "use_reentrant" not in gradient_checkpointing_kwargs or gradient_checkpointing_kwargs["use_reentrant"]:
+            # For backward compatibility
+            if hasattr(model, "enable_input_require_grads"):
+                model.enable_input_require_grads()
+            else:
 
-            def make_inputs_require_grad(module, input, output):
-                output.requires_grad_(True)
+                def make_inputs_require_grad(module, input, output):
+                    output.requires_grad_(True)
 
-            model.get_input_embeddings().register_forward_hook(make_inputs_require_grad)
+                model.get_input_embeddings().register_forward_hook(make_inputs_require_grad)
 
-        # enable gradient checkpointing for memory efficiency
-        model.gradient_checkpointing_enable()
+        # To support older transformers versions, check if the model supports gradient_checkpointing_kwargs
+        _supports_gc_kwargs = "gradient_checkpointing_kwargs" in list(
+            inspect.signature(model.gradient_checkpointing_enable).parameters
+        )
 
+        if not _supports_gc_kwargs and len(gradient_checkpointing_kwargs) > 0:
+            warnings.warn(
+                "gradient_checkpointing_kwargs is not supported in this version of transformers. The passed kwargs will be ignored."
+                " if you want to use that feature, please upgrade to the latest version of transformers.",
+                FutureWarning,
+            )
+
+        gc_enable_kwargs = (
+            {} if not _supports_gc_kwargs else {"gradient_checkpointing_kwargs": gradient_checkpointing_kwargs}
+        )
+
+        # enable gradient checkpointing for memory efficiency
+        model.gradient_checkpointing_enable(**gc_enable_kwargs)
     return model