[trainer] make generate work with multigpu (#8716)

* make generate work with multigpu

* better fix - thanks @sgugger

examples/seq2seq/seq2seq_trainer.py

@@ -189,7 +189,7 @@ class Seq2SeqTrainer(Trainer):
         }
 
         if self.args.predict_with_generate and not self.args.prediction_loss_only:
-            generated_tokens = model.generate(
+            generated_tokens = self.model.generate(
                 inputs["input_ids"],
                 attention_mask=inputs["attention_mask"],
                 **gen_kwargs,

examples/seq2seq/test_finetune_trainer.py

@@ -4,13 +4,7 @@ from unittest.mock import patch
 
 from transformers import BertTokenizer, EncoderDecoderModel
 from transformers.file_utils import is_datasets_available
-from transformers.testing_utils import (
-    TestCasePlus,
-    execute_subprocess_async,
-    get_gpu_count,
-    require_torch_non_multi_gpu_but_fix_me,
-    slow,
-)
+from transformers.testing_utils import TestCasePlus, execute_subprocess_async, get_gpu_count, slow
 from transformers.trainer_callback import TrainerState
 from transformers.trainer_utils import set_seed
 
@@ -52,7 +46,6 @@ class TestFinetuneTrainer(TestCasePlus):
         assert "test_results.json" in contents
 
     @slow
-    @require_torch_non_multi_gpu_but_fix_me
     def test_finetune_bert2bert(self):
         if not is_datasets_available():
             return