From c1c895a36b420d58431cf483bd3ed602227892fc Mon Sep 17 00:00:00 2001
From: Jeffrey Wilcke <geffobscura@gmail.com>
Date: Sat, 25 Jul 2015 21:48:53 +0200
Subject: [PATCH] core: fixed genesis write out to write only canon number

---
 core/chain_util.go | 13 +++++++++++--
 core/genesis.go    |  9 ++++++++-
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/core/chain_util.go b/core/chain_util.go
index a67fdb135..38273d2f0 100644
--- a/core/chain_util.go
+++ b/core/chain_util.go
@@ -111,13 +111,22 @@ func GetBlockByNumber(db common.Database, number uint64) *types.Block {
 	return GetBlockByHash(db, common.BytesToHash(key))
 }
 
-// WriteHead force writes the current head
-func WriteHead(db common.Database, block *types.Block) error {
+// WriteCanonNumber writes the canonical hash for the given block
+func WriteCanonNumber(db common.Database, block *types.Block) error {
 	key := append(blockNumPre, block.Number().Bytes()...)
 	err := db.Put(key, block.Hash().Bytes())
 	if err != nil {
 		return err
 	}
+	return nil
+}
+
+// WriteHead force writes the current head
+func WriteHead(db common.Database, block *types.Block) error {
+	err := WriteCanonNumber(db, block)
+	if err != nil {
+		return err
+	}
 	err = db.Put([]byte("LastBlock"), block.Hash().Bytes())
 	if err != nil {
 		return err
diff --git a/core/genesis.go b/core/genesis.go
index a88e88ea8..2f218724a 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -27,6 +27,8 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/params"
 )
 
@@ -83,7 +85,12 @@ func WriteGenesisBlock(stateDb, blockDb common.Database, reader io.Reader) (*typ
 	block.Td = difficulty
 
 	if block := GetBlockByHash(blockDb, block.Hash()); block != nil {
-		return nil, fmt.Errorf("Block %x already in database", block.Hash())
+		glog.V(logger.Info).Infoln("Genesis block already in chain. Writing canonical number")
+		err := WriteCanonNumber(blockDb, block)
+		if err != nil {
+			return nil, err
+		}
+		return block, nil
 	}
 
 	statedb.Sync()