core, trie: flush preimages to db on blockchain close (ethereum#25533)

* core, trie: flush preimages to db on database close

Co-authored-by: rjl493456442 <garyrong0905@gmail.com>

* rename Close to CommitPreimages for clarity

* core, trie: nitpick fixes

Co-authored-by: rjl493456442 <garyrong0905@gmail.com>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

core/blockchain.go

@@ -894,6 +894,10 @@ func (bc *BlockChain) Stop() {
 			log.Error("Dangling trie nodes after full cleanup")
 		}
 	}
+	// Flush the collected preimages to disk
+	if err := bc.stateCache.TrieDB().CommitPreimages(); err != nil {
+		log.Error("Failed to commit trie preimages", "err", err)
+	}
 	// Ensure all live cached entries be saved into disk, so that we can skip
 	// cache warmup when node restarts.
 	if bc.cacheConfig.TrieCleanJournal != "" {

trie/database.go

@@ -852,3 +852,16 @@ func (db *Database) SaveCachePeriodically(dir string, interval time.Duration, st
 		}
 	}
 }
+
+// CommitPreimages flushes the dangling preimages to disk. It is meant to be
+// called when closing the blockchain object, so that preimages are persisted
+// to the database.
+func (db *Database) CommitPreimages() error {
+	db.lock.Lock()
+	defer db.lock.Unlock()
+
+	if db.preimages == nil {
+		return nil
+	}
+	return db.preimages.commit(true)
+}