Find the absent when starting the execution (#4248)

* find the absent when starting the execution

sync/src/tasks/block_sync_task.rs

@@ -423,15 +423,13 @@ where
         Ok(())
     }
 
-    async fn find_absent_ancestor(&self, mut block_headers: Vec<BlockHeader>) -> Result<u64> {
-        let mut count: u64 = 0;
+    async fn find_absent_ancestor(&self, mut block_headers: Vec<BlockHeader>) -> Result<()> {
         loop {
             let mut absent_blocks = vec![];
             self.find_absent_parent_dag_blocks_for_blocks(block_headers, &mut absent_blocks)?;
             if absent_blocks.is_empty() {
-                return Ok(count);
+                return Ok(());
             }
-            count = count.saturating_add(absent_blocks.len() as u64);
             block_headers = self.fetch_blocks(absent_blocks).await?;
         }
     }
@@ -453,17 +451,12 @@ where
             block_header.parents_hash()
         );
         let fut = async {
-            let count = self
-                .find_absent_ancestor(vec![block_header.clone()])
-                .await?;
-
-            if count == 0 {
-                return anyhow::Ok(ParallelSign::Continue);
-            }
-
             if block_header.number() % ASYNC_BLOCK_COUNT == 0
                 || block_header.number() >= self.target.target_id.number()
             {
+                self.find_absent_ancestor(vec![block_header.clone()])
+                    .await?;
+
                 let parallel_execute = DagBlockSender::new(
                     self.sync_dag_store.clone(),
                     100000,