From 7ef43c941803876f7bbf1c8913365f1b9a1a60cd Mon Sep 17 00:00:00 2001
From: imbr92 <40306754+imbr92@users.noreply.github.com>
Date: Wed, 18 Jun 2025 10:42:34 -0500
Subject: [PATCH] Add --lora_alpha and metadata handling to
 train_dreambooth_lora_sana.py

---
 .../dreambooth/test_dreambooth_lora_sana.py   | 42 +++++++++++++++++++
 .../dreambooth/train_dreambooth_lora_sana.py  | 18 ++++++--
 2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/examples/dreambooth/test_dreambooth_lora_sana.py b/examples/dreambooth/test_dreambooth_lora_sana.py
index 6e5727ae7176..7564ab08b028 100644
--- a/examples/dreambooth/test_dreambooth_lora_sana.py
+++ b/examples/dreambooth/test_dreambooth_lora_sana.py
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
 import logging
 import os
 import sys
@@ -20,6 +21,8 @@
 
 import safetensors
 
+from diffusers.loaders.lora_base import LORA_ADAPTER_METADATA_KEY
+
 
 sys.path.append("..")
 from test_examples_utils import ExamplesTestsAccelerate, run_command  # noqa: E402
@@ -204,3 +207,42 @@ def test_dreambooth_lora_sana_checkpointing_checkpoints_total_limit_removes_mult
             run_command(self._launch_args + resume_run_args)
 
             self.assertEqual({x for x in os.listdir(tmpdir) if "checkpoint" in x}, {"checkpoint-6", "checkpoint-8"})
+
+    def test_dreambooth_lora_sana_with_metadata(self):
+        lora_alpha = 8
+        rank = 4
+        with tempfile.TemporaryDirectory() as tmpdir:
+            test_args = f"""
+            {self.script_path}
+            --pretrained_model_name_or_path={self.pretrained_model_name_or_path}
+            --instance_data_dir={self.instance_data_dir}
+            --output_dir={tmpdir}
+            --resolution=32
+            --train_batch_size=1
+            --gradient_accumulation_steps=1
+            --max_train_steps=4
+            --lora_alpha={lora_alpha}
+            --rank={rank}
+            --checkpointing_steps=2
+            --max_sequence_length 166
+            """.split()
+
+            test_args.extend(["--instance_prompt", ""])
+            run_command(self._launch_args + test_args)
+
+            state_dict_file = os.path.join(tmpdir, "pytorch_lora_weights.safetensors")
+            self.assertTrue(os.path.isfile(state_dict_file))
+
+            # Check if the metadata was properly serialized.
+            with safetensors.torch.safe_open(state_dict_file, framework="pt", device="cpu") as f:
+                metadata = f.metadata() or {}
+
+            metadata.pop("format", None)
+            raw = metadata.get(LORA_ADAPTER_METADATA_KEY)
+            if raw:
+                raw = json.loads(raw)
+
+            loaded_lora_alpha = raw["transformer.lora_alpha"]
+            self.assertTrue(loaded_lora_alpha == lora_alpha)
+            loaded_lora_rank = raw["transformer.r"]
+            self.assertTrue(loaded_lora_rank == rank)
diff --git a/examples/dreambooth/train_dreambooth_lora_sana.py b/examples/dreambooth/train_dreambooth_lora_sana.py
index 0c4a16d1802f..c156523db3d5 100644
--- a/examples/dreambooth/train_dreambooth_lora_sana.py
+++ b/examples/dreambooth/train_dreambooth_lora_sana.py
@@ -52,6 +52,7 @@
 )
 from diffusers.optimization import get_scheduler
 from diffusers.training_utils import (
+    _collate_lora_metadata,
     cast_training_params,
     compute_density_for_timestep_sampling,
     compute_loss_weighting_for_sd3,
@@ -323,9 +324,13 @@ def parse_args(input_args=None):
         default=4,
         help=("The dimension of the LoRA update matrices."),
     )
-
+    parser.add_argument(
+        "--lora_alpha",
+        type=int,
+        default=4,
+        help="LoRA alpha to be used for additional scaling.",
+    )
     parser.add_argument("--lora_dropout", type=float, default=0.0, help="Dropout probability for LoRA layers")
-
     parser.add_argument(
         "--with_prior_preservation",
         default=False,
@@ -1023,7 +1028,7 @@ def main(args):
     # now we will add new LoRA weights the transformer layers
     transformer_lora_config = LoraConfig(
         r=args.rank,
-        lora_alpha=args.rank,
+        lora_alpha=args.lora_alpha,
         lora_dropout=args.lora_dropout,
         init_lora_weights="gaussian",
         target_modules=target_modules,
@@ -1039,10 +1044,11 @@ def unwrap_model(model):
     def save_model_hook(models, weights, output_dir):
         if accelerator.is_main_process:
             transformer_lora_layers_to_save = None
-
+            modules_to_save = {}
             for model in models:
                 if isinstance(model, type(unwrap_model(transformer))):
                     transformer_lora_layers_to_save = get_peft_model_state_dict(model)
+                    modules_to_save["transformer"] = model
                 else:
                     raise ValueError(f"unexpected save model: {model.__class__}")
 
@@ -1052,6 +1058,7 @@ def save_model_hook(models, weights, output_dir):
             SanaPipeline.save_lora_weights(
                 output_dir,
                 transformer_lora_layers=transformer_lora_layers_to_save,
+                **_collate_lora_metadata(modules_to_save),
             )
 
     def load_model_hook(models, input_dir):
@@ -1507,15 +1514,18 @@ def get_sigmas(timesteps, n_dim=4, dtype=torch.float32):
     accelerator.wait_for_everyone()
     if accelerator.is_main_process:
         transformer = unwrap_model(transformer)
+        modules_to_save = {}
         if args.upcast_before_saving:
             transformer.to(torch.float32)
         else:
             transformer = transformer.to(weight_dtype)
         transformer_lora_layers = get_peft_model_state_dict(transformer)
+        modules_to_save["transformer"] = transformer
 
         SanaPipeline.save_lora_weights(
             save_directory=args.output_dir,
             transformer_lora_layers=transformer_lora_layers,
+            **_collate_lora_metadata(modules_to_save),
         )
 
         # Final inference