[LED] fix global_attention_mask not being passed for generation and docs...

[LED] fix global_attention_mask not being passed for generation and docs clarification about grad checkpointing (#17112)

* [LED] fixed global_attention_mask not passed for generation + docs clarification for gradient checkpointing

* LED docs clarification
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* [LED] gradient_checkpointing=True should be passed to TrainingArguments
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* [LED] docs: remove wrong word
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* [LED] docs fix typo
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

docs/source/en/model_doc/led.mdx

@@ -44,8 +44,10 @@ Tips:
 - LED makes use of *global attention* by means of the `global_attention_mask` (see
   [`LongformerModel`]). For summarization, it is advised to put *global attention* only on the first
   `<s>` token. For question answering, it is advised to put *global attention* on all tokens of the question.
-- To fine-tune LED on all 16384, it is necessary to enable *gradient checkpointing* by executing
-  `model.gradient_checkpointing_enable()`.
+- To fine-tune LED on all 16384, *gradient checkpointing* can be enabled in case training leads to out-of-memory (OOM)
+  errors. This can be done by executing `model.gradient_checkpointing_enable()`. 
+ Moreover, the `use_cache=False`
+  flag can be used to disable the caching mechanism to save memory.
 - A notebook showing how to evaluate LED, can be accessed [here](https://colab.research.google.com/drive/12INTTR6n64TzS4RrXZxMSXfrOd9Xzamo?usp=sharing).
 - A notebook showing how to fine-tune LED, can be accessed [here](https://colab.research.google.com/drive/12LjJazBl7Gam0XBPy_y0CTOJZeZ34c2v?usp=sharing).
 

src/transformers/models/led/modeling_led.py

@@ -2441,6 +2441,7 @@ class LEDForConditionalGeneration(LEDPreTrainedModel):
         decoder_input_ids,
         past=None,
         attention_mask=None,
+        global_attention_mask=None,
         head_mask=None,
         decoder_head_mask=None,
         cross_attn_head_mask=None,
@@ -2458,6 +2459,7 @@ class LEDForConditionalGeneration(LEDPreTrainedModel):
             "past_key_values": past,
             "decoder_input_ids": decoder_input_ids,
             "attention_mask": attention_mask,
+            "global_attention_mask": global_attention_mask,
             "head_mask": head_mask,
             "decoder_head_mask": decoder_head_mask,
             "cross_attn_head_mask": cross_attn_head_mask,