blockchain: NodeStatus & Set/UnsetStatusFlags methods on blockIndex.

These method allows safe concurrent access to reading and modifying
block node statuses. When block statuses get persisted in a later
change, the setter methods can be used to mark block nodes as dirty.

blockchain/accept.go

@@ -29,7 +29,7 @@ func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags)
 	if prevNode == nil {
 		str := fmt.Sprintf("previous block %s is unknown", prevHash)
 		return false, ruleError(ErrPreviousBlockUnknown, str)
-	} else if prevNode.KnownInvalid() {
+	} else if b.index.NodeStatus(prevNode).KnownInvalid() {
 		str := fmt.Sprintf("previous block %s is known to be invalid", prevHash)
 		return false, ruleError(ErrInvalidAncestorBlock, str)
 	}
@@ -64,7 +64,7 @@ func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags)
 	// block chain (could be either a side chain or the main chain).
 	blockHeader := &block.MsgBlock().Header
 	newNode := newBlockNode(blockHeader, blockHeight)
-	newNode.status |= statusDataStored
+	newNode.status = statusDataStored
 	if prevNode != nil {
 		newNode.parent = prevNode
 		newNode.height = blockHeight

blockchain/blockindex.go

@@ -39,6 +39,27 @@ const (
 	statusNone blockStatus = 0
 )
 
+// HaveData returns whether the full block data is stored in the database. This
+// will return false for a block node where only the header is downloaded or
+// kept.
+func (status blockStatus) HaveData() bool {
+	return status&statusDataStored != 0
+}
+
+// KnownValid returns whether the block is known to be valid. This will return
+// false for a valid block that has not been fully validated yet.
+func (status blockStatus) KnownValid() bool {
+	return status&statusValid != 0
+}
+
+// KnownInvalid returns whether the block is known to be invalid. This may be
+// because the block itself failed validation or any of its ancestors is
+// invalid. This will return false for invalid blocks that have not been proven
+// invalid yet.
+func (status blockStatus) KnownInvalid() bool {
+	return status&(statusValidateFailed|statusInvalidAncestor) != 0
+}
+
 // blockNode represents a block within the block chain and is primarily used to
 // aid in selecting the best chain to be the main chain.  The main chain is
 // stored into the block database.
@@ -73,7 +94,10 @@ type blockNode struct {
 	timestamp  int64
 	merkleRoot chainhash.Hash
 
-	// status is a bitfield representing the validation state of the block
+	// status is a bitfield representing the validation state of the block. The
+	// status field, unlike the other fields, may be written to and so should
+	// only be accessed using the concurrent-safe NodeStatus method on
+	// blockIndex once the node has been added to the global index.
 	status blockStatus
 }
 
@@ -193,20 +217,6 @@ func (node *blockNode) CalcPastMedianTime() time.Time {
 	return time.Unix(medianTimestamp, 0)
 }
 
-// KnownValid returns whether the block is known to be valid. This will return
-// false for a valid block that has not been fully validated yet.
-func (node *blockNode) KnownValid() bool {
-	return node.status&statusValid != 0
-}
-
-// KnownInvalid returns whether the block is known to be invalid. This may be
-// because the block itself failed validation or any of its ancestors is
-// invalid. This will return false for invalid blocks that have not been proven
-// invalid yet.
-func (node *blockNode) KnownInvalid() bool {
-	return node.status&(statusValidateFailed|statusInvalidAncestor) != 0
-}
-
 // blockIndex provides facilities for keeping track of an in-memory index of the
 // block chain.  Although the name block chain suggests a single chain of
 // blocks, it is actually a tree-shaped structure where any node can have
@@ -265,13 +275,33 @@ func (bi *blockIndex) AddNode(node *blockNode) {
 	bi.Unlock()
 }
 
-// RemoveNode removes the provided node from the block index.  There is no check
+// NodeStatus provides concurrent-safe access to the status field of a node.
-// whether another node in the index depends on this one, so it is up to caller
-// to avoid that situation.
 //
 // This function is safe for concurrent access.
-func (bi *blockIndex) RemoveNode(node *blockNode) {
+func (bi *blockIndex) NodeStatus(node *blockNode) blockStatus {
+	bi.RLock()
+	status := node.status
+	bi.RUnlock()
+	return status
+}
+
+// SetStatusFlags flips the provided status flags on the block node to on,
+// regardless of whether they were on or off previously. This does not unset any
+// flags currently on.
+//
+// This function is safe for concurrent access.
+func (bi *blockIndex) SetStatusFlags(node *blockNode, flags blockStatus) {
 	bi.Lock()
-	delete(bi.index, node.hash)
+	node.status |= flags
+	bi.Unlock()
+}
+
+// UnsetStatusFlags flips the provided status flags on the block node to off,
+// regardless of whether they were on or off previously.
+//
+// This function is safe for concurrent access.
+func (bi *blockIndex) UnsetStatusFlags(node *blockNode, flags blockStatus) {
+	bi.Lock()
+	node.status &^= flags
 	bi.Unlock()
 }

blockchain/chain.go

@@ -503,8 +503,8 @@ func (b *BlockChain) getReorganizeNodes(node *blockNode) (*list.List, *list.List
 	// Do not reorganize to a known invalid chain. Ancestors deeper than the
 	// direct parent are checked below but this is a quick check before doing
 	// more unnecessary work.
-	if node.parent.KnownInvalid() {
+	if b.index.NodeStatus(node.parent).KnownInvalid() {
-		node.status |= statusInvalidAncestor
+		b.index.SetStatusFlags(node, statusInvalidAncestor)
 		return detachNodes, attachNodes
 	}
 
@@ -515,7 +515,7 @@ func (b *BlockChain) getReorganizeNodes(node *blockNode) (*list.List, *list.List
 	forkNode := b.bestChain.FindFork(node)
 	invalidChain := false
 	for n := node; n != nil && n != forkNode; n = n.parent {
-		if n.KnownInvalid() {
+		if b.index.NodeStatus(n).KnownInvalid() {
 			invalidChain = true
 			break
 		}
@@ -529,7 +529,7 @@ func (b *BlockChain) getReorganizeNodes(node *blockNode) (*list.List, *list.List
 		for e := attachNodes.Front(); e != nil; e = next {
 			next = e.Next()
 			n := attachNodes.Remove(e).(*blockNode)
-			n.status |= statusInvalidAncestor
+			b.index.SetStatusFlags(n, statusInvalidAncestor)
 		}
 		return detachNodes, attachNodes
 	}
@@ -882,7 +882,7 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 		// If any previous nodes in attachNodes failed validation,
 		// mark this one as having an invalid ancestor.
 		if validationError != nil {
-			n.status |= statusInvalidAncestor
+			b.index.SetStatusFlags(n, statusInvalidAncestor)
 			continue
 		}
 
@@ -902,7 +902,7 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 		// Skip checks if node has already been fully validated. Although
 		// checkConnectBlock gets skipped, we still need to update the UTXO
 		// view.
-		if n.KnownValid() {
+		if b.index.NodeStatus(n).KnownValid() {
 			err = view.fetchInputUtxos(b.db, block)
 			if err != nil {
 				return err
@@ -924,13 +924,13 @@ func (b *BlockChain) reorganizeChain(detachNodes, attachNodes *list.List) error
 			// continue to loop through remaining nodes, marking them as
 			// having an invalid ancestor.
 			if _, ok := err.(RuleError); ok {
-				n.status |= statusValidateFailed
+				b.index.SetStatusFlags(n, statusValidateFailed)
 				validationError = err
 				continue
 			}
 			return err
 		}
-		n.status |= statusValid
+		b.index.SetStatusFlags(n, statusValid)
 	}
 
 	if validationError != nil {
@@ -1034,7 +1034,7 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 	parentHash := &block.MsgBlock().Header.PrevBlock
 	if parentHash.IsEqual(&b.bestChain.Tip().hash) {
 		// Skip checks if node has already been fully validated.
-		fastAdd = fastAdd || node.KnownValid()
+		fastAdd = fastAdd || b.index.NodeStatus(node).KnownValid()
 
 		// Perform several checks to verify the block can be connected
 		// to the main chain without violating any rules and without
@@ -1046,11 +1046,11 @@ func (b *BlockChain) connectBestChain(node *blockNode, block *btcutil.Block, fla
 			err := b.checkConnectBlock(node, block, view, &stxos)
 			if err != nil {
 				if _, ok := err.(RuleError); ok {
-					node.status |= statusValidateFailed
+					b.index.SetStatusFlags(node, statusValidateFailed)
 				}
 				return false, err
 			}
-			node.status |= statusValid
+			b.index.SetStatusFlags(node, statusValid)
 		}
 
 		// In the fast add case the code to check the block connection

blockchain/chainio.go

@@ -1060,7 +1060,7 @@ func (b *BlockChain) createChainState() error {
 	genesisBlock := btcutil.NewBlock(b.chainParams.GenesisBlock)
 	header := &genesisBlock.MsgBlock().Header
 	node := newBlockNode(header, 0)
-	node.status |= statusDataStored | statusValid
+	node.status = statusDataStored | statusValid
 	b.bestChain.SetTip(node)
 
 	// Add the new node to the index which is used for faster lookups.
@@ -1165,7 +1165,7 @@ func (b *BlockChain) initChainState() error {
 			// and add it to the block index.
 			node := &blockNodes[height]
 			initBlockNode(node, header, height)
-			node.status |= statusDataStored | statusValid
+			node.status = statusDataStored | statusValid
 			if tip != nil {
 				node.parent = tip
 				node.workSum = node.workSum.Add(tip.workSum,