From 33f6c22607c9d338ca2fb4e38666efe382504311 Mon Sep 17 00:00:00 2001
From: Nishant Das <nishdas93@gmail.com>
Date: Fri, 27 Mar 2020 09:06:30 +0800
Subject: [PATCH] Revert "Add Fast Copy of Trie" (#5228)

* Revert "new fixes (#5221)"

This reverts commit 4118fa52420eb104bdb10881379a3e99cec66571.
---
 beacon-chain/blockchain/head.go               | 16 ++++++-------
 beacon-chain/blockchain/process_block.go      |  2 +-
 .../blockchain/process_block_helpers.go       |  2 +-
 beacon-chain/state/state_trie.go              | 23 -------------------
 4 files changed, 10 insertions(+), 33 deletions(-)

diff --git a/beacon-chain/blockchain/head.go b/beacon-chain/blockchain/head.go
index 618e6f355af3..7c70d0616908 100644
--- a/beacon-chain/blockchain/head.go
+++ b/beacon-chain/blockchain/head.go
@@ -127,17 +127,17 @@ func (s *Service) saveHeadNoDB(ctx context.Context, b *ethpb.SignedBeaconBlock,
 			return errors.Wrap(err, "could not retrieve head state in DB")
 		}
 	} else {
-		s.initSyncStateLock.RLock()
-		cachedHeadState, ok := s.initSyncState[r]
-		if ok {
-			headState = cachedHeadState
+		headState, err = s.beaconDB.State(ctx, r)
+		if err != nil {
+			return errors.Wrap(err, "could not retrieve head state in DB")
 		}
-		s.initSyncStateLock.RUnlock()
 		if headState == nil {
-			headState, err = s.beaconDB.State(ctx, r)
-			if err != nil {
-				return errors.Wrap(err, "could not retrieve head state in DB")
+			s.initSyncStateLock.RLock()
+			cachedHeadState, ok := s.initSyncState[r]
+			if ok {
+				headState = cachedHeadState
 			}
+			s.initSyncStateLock.RUnlock()
 		}
 	}
 	if headState == nil {
diff --git a/beacon-chain/blockchain/process_block.go b/beacon-chain/blockchain/process_block.go
index 60a1fa2e468b..313f406c20cf 100644
--- a/beacon-chain/blockchain/process_block.go
+++ b/beacon-chain/blockchain/process_block.go
@@ -229,7 +229,7 @@ func (s *Service) onBlockInitialSyncStateTransition(ctx context.Context, signed
 	} else {
 		s.initSyncStateLock.Lock()
 		defer s.initSyncStateLock.Unlock()
-		s.initSyncState[root] = postState.FastCopy()
+		s.initSyncState[root] = postState.Copy()
 		s.filterBoundaryCandidates(ctx, root, postState)
 	}
 
diff --git a/beacon-chain/blockchain/process_block_helpers.go b/beacon-chain/blockchain/process_block_helpers.go
index 7d6e59a8dabe..9c9d211b425b 100644
--- a/beacon-chain/blockchain/process_block_helpers.go
+++ b/beacon-chain/blockchain/process_block_helpers.go
@@ -99,7 +99,7 @@ func (s *Service) verifyBlkPreState(ctx context.Context, b *ethpb.BeaconBlock) (
 		}
 		return preState, nil // No copy needed from newly hydrated DB object.
 	}
-	return preState.FastCopy(), nil
+	return preState.Copy(), nil
 }
 
 // verifyBlkDescendant validates input block root is a descendant of the
diff --git a/beacon-chain/state/state_trie.go b/beacon-chain/state/state_trie.go
index 0ad1f9c0ccae..a73587b7902e 100644
--- a/beacon-chain/state/state_trie.go
+++ b/beacon-chain/state/state_trie.go
@@ -177,29 +177,6 @@ func (b *BeaconState) Copy() *BeaconState {
 	return dst
 }
 
-// FastCopy is used to copy all the field trie contents and
-// empty out the references to it in the source state. This
-// is used when we have a state that we know will most
-// likely not be used anytime in the future.
-func (b *BeaconState) FastCopy() *BeaconState {
-	newState := b.Copy()
-	for fldIdx, fieldTrie := range b.stateFieldLeaves {
-		if fieldTrie.reference != nil {
-			fieldTrie.Lock()
-			fieldTrie.MinusRef()
-			fieldTrie.Unlock()
-			b.rebuildTrie[fldIdx] = true
-			b.dirtyFields[fldIdx] = true
-			b.stateFieldLeaves[fldIdx] = &FieldTrie{
-				field:     fldIdx,
-				reference: &reference{1},
-				Mutex:     new(sync.Mutex),
-			}
-		}
-	}
-	return newState
-}
-
 // HashTreeRoot of the beacon state retrieves the Merkle root of the trie
 // representation of the beacon state based on the eth2 Simple Serialize specification.
 func (b *BeaconState) HashTreeRoot(ctx context.Context) ([32]byte, error) {