[Core] Small simplification in `GPUModelRunner._update_states()` (#26508)

Signed-off-by: Nick Hill <nhill@redhat.com>

vllm/v1/worker/gpu_model_runner.py

@@ -708,6 +708,7 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             # Update the cached states.
 
             req_state.num_computed_tokens = num_computed_tokens
+            req_index = self.input_batch.req_id_to_index.get(req_id)
 
             if not is_last_rank:
                 # When using PP, the scheduler sends the sampled tokens back,
@@ -728,19 +729,13 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
                 # Some output tokens were discarded due to a sync-KV-load
                 # failure. Align the cached state.
                 del req_state.output_token_ids[num_output_tokens:]
-
-                req_index = self.input_batch.req_id_to_index.get(req_id)
                 if req_index is not None:
-                    old_end_idx = self.input_batch.num_tokens_no_spec[req_index]
                     end_idx = (
                         self.input_batch.num_prompt_tokens[req_index]
                         + num_output_tokens
                     )
                     self.input_batch.num_tokens[req_index] = end_idx
                     self.input_batch.num_tokens_no_spec[req_index] = end_idx
-                    self.input_batch.is_token_ids[req_index, end_idx:old_end_idx] = (
-                        False
-                    )
 
             # Update the block IDs.
             if not resumed_from_preemption:
@@ -749,12 +744,12 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
                     for block_ids, new_ids in zip(req_state.block_ids, new_block_ids):
                         block_ids.extend(new_ids)
             else:
+                assert req_index is None
                 assert new_block_ids is not None
                 # The request is resumed from preemption.
                 # Replace the existing block IDs with the new ones.
                 req_state.block_ids = new_block_ids
 
-            req_index = self.input_batch.req_id_to_index.get(req_id)
             if req_index is None:
                 # The request is not in the persistent batch.
                 # The request was either preempted and resumed later, or was not