fix group offloading when using torchao

src/diffusers/hooks/group_offloading.py

@@ -22,7 +22,7 @@ from typing import Set
 import safetensors.torch
 import torch
 
-from ..utils import get_logger, is_accelerate_available
+from ..utils import get_logger, is_accelerate_available, is_torchao_available
 from ._common import _GO_LC_SUPPORTED_PYTORCH_LAYERS
 from .hooks import HookRegistry, ModelHook
 
@@ -35,6 +35,41 @@ if is_accelerate_available():
 logger = get_logger(__name__)  # pylint: disable=invalid-name
 
 
+def _is_torchao_tensor(tensor: torch.Tensor) -> bool:
+    """Check if a tensor is a TorchAO quantized tensor subclass."""
+    if not is_torchao_available():
+        return False
+    from torchao.utils import TorchAOBaseTensor
+
+    return isinstance(tensor, TorchAOBaseTensor)
+
+
+def _get_torchao_inner_tensor_names(tensor: torch.Tensor) -> list[str]:
+    """Get names of all internal tensor data attributes from a TorchAO tensor."""
+    cls = type(tensor)
+    names = list(getattr(cls, "tensor_data_names", []))
+    for attr_name in getattr(cls, "optional_tensor_data_names", []):
+        if getattr(tensor, attr_name, None) is not None:
+            names.append(attr_name)
+    return names
+
+
+def _update_torchao_tensor_in_place(param: torch.Tensor, source: torch.Tensor) -> None:
+    """Update internal tensor data of a TorchAO parameter in-place from source.
+
+    Must operate on the parameter/buffer object directly (not ``param.data``) because ``_make_wrapper_subclass``
+    returns a fresh wrapper from ``.data`` each time, so attribute mutations on ``.data`` are lost.
+    """
+    for attr_name in _get_torchao_inner_tensor_names(source):
+        setattr(param, attr_name, getattr(source, attr_name))
+
+
+def _record_stream_torchao_tensor(param: torch.Tensor, stream) -> None:
+    """Record stream for all internal tensors of a TorchAO parameter."""
+    for attr_name in _get_torchao_inner_tensor_names(param):
+        getattr(param, attr_name).record_stream(stream)
+
+
 # fmt: off
 _GROUP_OFFLOADING = "group_offloading"
 _LAYER_EXECUTION_TRACKER = "layer_execution_tracker"
@@ -157,9 +192,16 @@ class ModuleGroup:
             pinned_dict = None
 
     def _transfer_tensor_to_device(self, tensor, source_tensor, default_stream):
-        tensor.data = source_tensor.to(self.onload_device, non_blocking=self.non_blocking)
+        moved = source_tensor.to(self.onload_device, non_blocking=self.non_blocking)
+        if _is_torchao_tensor(tensor):
+            _update_torchao_tensor_in_place(tensor, moved)
+        else:
+            tensor.data = moved
         if self.record_stream:
-            tensor.data.record_stream(default_stream)
+            if _is_torchao_tensor(tensor):
+                _record_stream_torchao_tensor(tensor, default_stream)
+            else:
+                tensor.data.record_stream(default_stream)
 
     def _process_tensors_from_modules(self, pinned_memory=None, default_stream=None):
         for group_module in self.modules:
@@ -245,18 +287,35 @@ class ModuleGroup:
 
             for group_module in self.modules:
                 for param in group_module.parameters():
-                    param.data = self.cpu_param_dict[param]
+                    if _is_torchao_tensor(param):
+                        _update_torchao_tensor_in_place(param, self.cpu_param_dict[param])
+                    else:
+                        param.data = self.cpu_param_dict[param]
             for param in self.parameters:
-                param.data = self.cpu_param_dict[param]
+                if _is_torchao_tensor(param):
+                    _update_torchao_tensor_in_place(param, self.cpu_param_dict[param])
+                else:
+                    param.data = self.cpu_param_dict[param]
             for buffer in self.buffers:
-                buffer.data = self.cpu_param_dict[buffer]
+                if _is_torchao_tensor(buffer):
+                    _update_torchao_tensor_in_place(buffer, self.cpu_param_dict[buffer])
+                else:
+                    buffer.data = self.cpu_param_dict[buffer]
         else:
             for group_module in self.modules:
                 group_module.to(self.offload_device, non_blocking=False)
             for param in self.parameters:
-                param.data = param.data.to(self.offload_device, non_blocking=False)
+                if _is_torchao_tensor(param):
+                    moved = param.data.to(self.offload_device, non_blocking=False)
+                    _update_torchao_tensor_in_place(param, moved)
+                else:
+                    param.data = param.data.to(self.offload_device, non_blocking=False)
             for buffer in self.buffers:
-                buffer.data = buffer.data.to(self.offload_device, non_blocking=False)
+                if _is_torchao_tensor(buffer):
+                    moved = buffer.data.to(self.offload_device, non_blocking=False)
+                    _update_torchao_tensor_in_place(buffer, moved)
+                else:
+                    buffer.data = buffer.data.to(self.offload_device, non_blocking=False)
 
     @torch.compiler.disable()
     def onload_(self):