[v1] Support meta loading for full and free (#10236)

src/llamafactory/v1/plugins/model_plugins/peft.py

@@ -150,6 +150,9 @@ def load_adapter(model: HFModel, adapter_name_or_path: Union[list[str], str], is
 
 @PeftPlugin("lora").register()
 def get_lora_model(model: HFModel, config: LoraConfigDict, is_train: bool = False) -> HFModel:
+    if model.device.type == "meta":
+        raise ValueError("Currently lora stage does not support loading model by meta.")
+
     adapter_name_or_path = config.get("adapter_name_or_path")
 
     if adapter_name_or_path:

src/llamafactory/v1/plugins/trainer_plugins/distributed/fsdp2.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import copy
 import gc
 import os
 
@@ -212,10 +213,52 @@ class FSDP2Engine:
 
         return model
 
+    def _save_non_persistent_buffers(self, model: HFModel) -> dict:
+        """Save non-persistent buffers, such as inv_freq."""
+        saved = {}
+        for mod_name, module in model.named_modules():
+            for buf_name in module._non_persistent_buffers_set:
+                fqn = f"{mod_name}.{buf_name}" if mod_name else buf_name
+                buf = getattr(module, buf_name, None)
+                if buf is not None:
+                    saved[fqn] = copy.deepcopy(buf)
+        if self.rank == 0 and saved:
+            logger.info(f"Saved {len(saved)} non-persistent buffers")
+        return saved
+
+    def _restore_non_persistent_buffers(self, model: HFModel, saved_buffers: dict):
+        """Register saved non-persistent buffers to model."""
+        if not saved_buffers:
+            return
+        device = get_current_accelerator()
+        for fqn, buf in saved_buffers.items():
+            buf = buf.to(device)
+            if "." in fqn:
+                parent_fqn, buf_name = fqn.rsplit(".", 1)
+                parent_module = model.get_submodule(parent_fqn)
+            else:
+                buf_name = fqn
+                parent_module = model
+            parent_module.register_buffer(buf_name, buf, persistent=False)
+        if self.rank == 0:
+            logger.info(f"Restored {len(saved_buffers)} non-persistent buffers")
+
     def shard_model(self, model: HFModel) -> HFModel:
         if model.device.type == "meta":
+            non_persistent_buffers = self._save_non_persistent_buffers(model)
+
+            if getattr(model.config, "tie_word_embeddings", None):
+                model.tie_weights()
+
             model = self.prepare_model(model)
             model = self.materialize_and_load(model, hf_model_path=model.config.name_or_path, dcp_path=self.dcp_path)
+
+            # fix tied broken for no-fsdp-wrap case
+            if getattr(model.config, "tie_word_embeddings", None):
+                model.tie_weights()
+
+            self._restore_non_persistent_buffers(model, non_persistent_buffers)
+
         else:
             model = self.prepare_model(model)
         return model