Address PR comments

core/blockchain.go

@@ -75,7 +75,7 @@ type CacheConfig struct {
 	TrieCleanLimit       int           // Memory allowance (MB) to use for caching trie nodes in memory
 	TrieDirtyLimit       int           // Memory limit (MB) at which to start flushing dirty trie nodes to disk
 	TrieTimeLimit        time.Duration // Time limit after which to flush the current in-memory trie to disk
-	ProcessStateDiffs bool
+	ProcessingStateDiffs bool          // Whether statediffs processing should be taken into a account before a trie is pruned
 }
 
 // BlockChain represents the canonical chain given a database with a genesis
@@ -928,14 +928,8 @@ func (bc *BlockChain) WriteBlockWithoutState(block *types.Block, td *big.Int) (e
 }
 
 func (bc *BlockChain) AddToStateDiffProcessedCollection(hash common.Hash) {
-	count, ok := bc.stateDiffsProcessed[hash]
-
-	if ok {
-		count++
-		bc.stateDiffsProcessed[hash] = count
-	} else {
-		bc.stateDiffsProcessed[hash] = 1
-	}
+	count := bc.stateDiffsProcessed[hash]
+	bc.stateDiffsProcessed[hash] = count + 1
 }
 
 // WriteBlockWithState writes the block and all associated state to the database.
@@ -1011,7 +1005,7 @@ func (bc *BlockChain) WriteBlockWithState(block *types.Block, receipts []*types.
 					break
 				}
 
-				if bc.cacheConfig.ProcessStateDiffs {
+				if bc.cacheConfig.ProcessingStateDiffs {
 					if !bc.allowedRootToBeDereferenced(root.(common.Hash)) {
 						bc.triegc.Push(root, number)
 						break
@@ -1074,7 +1068,9 @@ func (bc *BlockChain) WriteBlockWithState(block *types.Block, receipts []*types.
 	return status, nil
 }
 
-//if we haven't processed the statediff for a given state root and it's child, don't dereference it yet
+// since we need the state tries of the current block and its parent in-memory
+// in order to process statediffs, we should avoid dereferencing roots until
+// its statediff and its child have been processed
 func (bc *BlockChain) allowedRootToBeDereferenced(root common.Hash) bool {
 	diffProcessedForSelfAndChildCount := 2
 	count := bc.stateDiffsProcessed[root]

core/blockchain_test.go

@@ -1493,7 +1493,7 @@ func TestProcessingStateDiffs(t *testing.T) {
 		TrieCleanLimit:       defaultTrieCleanCache,
 		TrieDirtyLimit:       defaultTrieDirtyCache,
 		TrieTimeLimit:        defaultTrieTimeout,
-		ProcessStateDiffs: true,
+		ProcessingStateDiffs: true,
 	}
 	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)

eth/backend.go

@@ -161,7 +161,7 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 			TrieCleanLimit:       config.TrieCleanCache,
 			TrieDirtyLimit:       config.TrieDirtyCache,
 			TrieTimeLimit:        config.TrieTimeout,
-			ProcessStateDiffs: config.StateDiff,
+			ProcessingStateDiffs: config.StateDiff,
 		}
 	)
 	eth.blockchain, err = core.NewBlockChain(chainDb, cacheConfig, eth.chainConfig, eth.engine, vmConfig, eth.shouldPreserve)