From bf30cd4922ea62577d7bf63f5029e8be62665d45 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Mon, 24 Feb 2020 14:34:17 -0500
Subject: [PATCH 01/12] refactor: Add interfaces::FoundBlock class to
 selectively return block data

FoundBlock class allows interfaces::Chain::findBlock to return more block
information without having lots of optional output parameters. FoundBlock class
is also used by other chain methods in upcoming commits.

There is mostly no change in behavior. Only exception is
CWallet::RescanFromTime now throwing NonFatalCheckError instead of
std::logic_error.
---
 src/Makefile.test.include     |  1 +
 src/interfaces/chain.cpp      | 37 ++++++++++++++-------------
 src/interfaces/chain.h        | 30 ++++++++++++++++------
 src/sync.h                    |  2 +-
 src/test/interfaces_tests.cpp | 47 +++++++++++++++++++++++++++++++++++
 src/wallet/rpcwallet.cpp      |  7 +++---
 src/wallet/wallet.cpp         | 11 ++++----
 7 files changed, 99 insertions(+), 36 deletions(-)
 create mode 100644 src/test/interfaces_tests.cpp

diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 059876bec..a4d894680 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -198,6 +198,7 @@ BITCOIN_TESTS =\
   test/fs_tests.cpp \
   test/getarg_tests.cpp \
   test/hash_tests.cpp \
+  test/interfaces_tests.cpp \
   test/key_io_tests.cpp \
   test/key_tests.cpp \
   test/limitedmap_tests.cpp \
diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 0b3cd08e2..cfaf79f70 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -38,6 +38,21 @@
 namespace interfaces {
 namespace {
 
+bool FillBlock(const CBlockIndex* index, const FoundBlock& block, UniqueLock<RecursiveMutex>& lock)
+{
+    if (!index) return false;
+    if (block.m_hash) *block.m_hash = index->GetBlockHash();
+    if (block.m_height) *block.m_height = index->nHeight;
+    if (block.m_time) *block.m_time = index->GetBlockTime();
+    if (block.m_max_time) *block.m_max_time = index->GetBlockTimeMax();
+    if (block.m_mtp_time) *block.m_mtp_time = index->GetMedianTimePast();
+    if (block.m_data) {
+        REVERSE_LOCK(lock);
+        if (!ReadBlockFromDisk(*block.m_data, index, Params().GetConsensus())) block.m_data->SetNull();
+    }
+    return true;
+}
+
 class LockImpl : public Chain::Lock, public UniqueLock<RecursiveMutex>
 {
     Optional<int> getHeight() override
@@ -247,26 +262,10 @@ public:
         std::unique_ptr<Chain::Lock> result = std::move(lock); // Temporary to avoid CWG 1579
         return result;
     }
-    bool findBlock(const uint256& hash, CBlock* block, int64_t* time, int64_t* time_max) override
+    bool findBlock(const uint256& hash, const FoundBlock& block) override
     {
-        CBlockIndex* index;
-        {
-            LOCK(cs_main);
-            index = LookupBlockIndex(hash);
-            if (!index) {
-                return false;
-            }
-            if (time) {
-                *time = index->GetBlockTime();
-            }
-            if (time_max) {
-                *time_max = index->GetBlockTimeMax();
-            }
-        }
-        if (block && !ReadBlockFromDisk(*block, index, Params().GetConsensus())) {
-            block->SetNull();
-        }
-        return true;
+        WAIT_LOCK(cs_main, lock);
+        return FillBlock(LookupBlockIndex(hash), block, lock);
     }
     void findCoins(std::map<COutPoint, Coin>& coins) override { return FindCoins(m_node, coins); }
     double guessVerificationProgress(const uint256& block_hash) override
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index e1bc9bbbf..3778ab9a8 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -30,6 +30,27 @@ namespace interfaces {
 class Handler;
 class Wallet;
 
+//! Helper for findBlock to selectively return pieces of block data.
+class FoundBlock
+{
+public:
+    FoundBlock& hash(uint256& hash) { m_hash = &hash; return *this; }
+    FoundBlock& height(int& height) { m_height = &height; return *this; }
+    FoundBlock& time(int64_t& time) { m_time = &time; return *this; }
+    FoundBlock& maxTime(int64_t& max_time) { m_max_time = &max_time; return *this; }
+    FoundBlock& mtpTime(int64_t& mtp_time) { m_mtp_time = &mtp_time; return *this; }
+    //! Read block data from disk. If the block exists but doesn't have data
+    //! (for example due to pruning), the CBlock variable will be set to null.
+    FoundBlock& data(CBlock& data) { m_data = &data; return *this; }
+
+    uint256* m_hash = nullptr;
+    int* m_height = nullptr;
+    int64_t* m_time = nullptr;
+    int64_t* m_max_time = nullptr;
+    int64_t* m_mtp_time = nullptr;
+    CBlock* m_data = nullptr;
+};
+
 //! Interface giving clients (wallet processes, maybe other analysis tools in
 //! the future) ability to access to the chain state, receive notifications,
 //! estimate fees, and submit transactions.
@@ -127,14 +148,7 @@ public:
 
     //! Return whether node has the block and optionally return block metadata
     //! or contents.
-    //!
-    //! If a block pointer is provided to retrieve the block contents, and the
-    //! block exists but doesn't have data (for example due to pruning), the
-    //! block will be empty and all fields set to null.
-    virtual bool findBlock(const uint256& hash,
-        CBlock* block = nullptr,
-        int64_t* time = nullptr,
-        int64_t* max_time = nullptr) = 0;
+    virtual bool findBlock(const uint256& hash, const FoundBlock& block={}) = 0;
 
     //! Look up unspent output information. Returns coins in the mempool and in
     //! the current chain UTXO set. Iterates through all the keys in the map and
diff --git a/src/sync.h b/src/sync.h
index ead2cdc67..0c6f0ef0a 100644
--- a/src/sync.h
+++ b/src/sync.h
@@ -210,7 +210,7 @@ public:
      friend class reverse_lock;
 };
 
-#define REVERSE_LOCK(g) decltype(g)::reverse_lock PASTE2(revlock, __COUNTER__)(g, #g, __FILE__, __LINE__)
+#define REVERSE_LOCK(g) typename std::decay<decltype(g)>::type::reverse_lock PASTE2(revlock, __COUNTER__)(g, #g, __FILE__, __LINE__)
 
 template<typename MutexArg>
 using DebugLock = UniqueLock<typename std::remove_reference<typename std::remove_pointer<MutexArg>::type>::type>;
diff --git a/src/test/interfaces_tests.cpp b/src/test/interfaces_tests.cpp
new file mode 100644
index 000000000..e3d1738c7
--- /dev/null
+++ b/src/test/interfaces_tests.cpp
@@ -0,0 +1,47 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <interfaces/chain.h>
+#include <test/util/setup_common.h>
+#include <validation.h>
+
+#include <boost/test/unit_test.hpp>
+
+using interfaces::FoundBlock;
+
+BOOST_FIXTURE_TEST_SUITE(interfaces_tests, TestChain100Setup)
+
+BOOST_AUTO_TEST_CASE(findBlock)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+
+    uint256 hash;
+    BOOST_CHECK(chain->findBlock(active[10]->GetBlockHash(), FoundBlock().hash(hash)));
+    BOOST_CHECK_EQUAL(hash, active[10]->GetBlockHash());
+
+    int height = -1;
+    BOOST_CHECK(chain->findBlock(active[20]->GetBlockHash(), FoundBlock().height(height)));
+    BOOST_CHECK_EQUAL(height, active[20]->nHeight);
+
+    CBlock data;
+    BOOST_CHECK(chain->findBlock(active[30]->GetBlockHash(), FoundBlock().data(data)));
+    BOOST_CHECK_EQUAL(data.GetHash(), active[30]->GetBlockHash());
+
+    int64_t time = -1;
+    BOOST_CHECK(chain->findBlock(active[40]->GetBlockHash(), FoundBlock().time(time)));
+    BOOST_CHECK_EQUAL(time, active[40]->GetBlockTime());
+
+    int64_t max_time = -1;
+    BOOST_CHECK(chain->findBlock(active[50]->GetBlockHash(), FoundBlock().maxTime(max_time)));
+    BOOST_CHECK_EQUAL(max_time, active[50]->GetBlockTimeMax());
+
+    int64_t mtp_time = -1;
+    BOOST_CHECK(chain->findBlock(active[60]->GetBlockHash(), FoundBlock().mtpTime(mtp_time)));
+    BOOST_CHECK_EQUAL(mtp_time, active[60]->GetMedianTimePast());
+
+    BOOST_CHECK(!chain->findBlock({}, FoundBlock()));
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 5d34e592d..1e6d37c46 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -37,6 +37,8 @@
 #include <univalue.h>
 
 
+using interfaces::FoundBlock;
+
 static const std::string WALLET_ENDPOINT_BASE = "/wallet/";
 
 static inline bool GetAvoidReuseFlag(const CWallet* const pwallet, const UniValue& param) {
@@ -149,8 +151,7 @@ static void WalletTxToJSON(interfaces::Chain& chain, interfaces::Chain::Lock& lo
         entry.pushKV("blockheight", wtx.m_confirm.block_height);
         entry.pushKV("blockindex", wtx.m_confirm.nIndex);
         int64_t block_time;
-        bool found_block = chain.findBlock(wtx.m_confirm.hashBlock, nullptr /* block */, &block_time);
-        CHECK_NONFATAL(found_block);
+        CHECK_NONFATAL(chain.findBlock(wtx.m_confirm.hashBlock, FoundBlock().time(block_time)));
         entry.pushKV("blocktime", block_time);
     } else {
         entry.pushKV("trusted", wtx.IsTrusted(locked_chain));
@@ -1618,7 +1619,7 @@ static UniValue listsinceblock(const JSONRPCRequest& request)
     UniValue removed(UniValue::VARR);
     while (include_removed && altheight && *altheight > *height) {
         CBlock block;
-        if (!pwallet->chain().findBlock(blockId, &block) || block.IsNull()) {
+        if (!pwallet->chain().findBlock(blockId, FoundBlock().data(block)) || block.IsNull()) {
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Can't read block from disk");
         }
         for (const CTransactionRef& tx : block.vtx) {
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 98f308f92..c8641b03f 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -22,6 +22,7 @@
 #include <script/script.h>
 #include <script/signingprovider.h>
 #include <util/bip32.h>
+#include <util/check.h>
 #include <util/error.h>
 #include <util/fees.h>
 #include <util/moneystr.h>
@@ -35,6 +36,8 @@
 
 #include <boost/algorithm/string/replace.hpp>
 
+using interfaces::FoundBlock;
+
 const std::map<uint64_t,std::string> WALLET_FLAG_CAVEATS{
     {WALLET_FLAG_AVOID_REUSE,
         "You need to rescan the blockchain in order to correctly mark used "
@@ -1601,9 +1604,7 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
         ScanResult result = ScanForWalletTransactions(start_block, {} /* stop_block */, reserver, update);
         if (result.status == ScanResult::FAILURE) {
             int64_t time_max;
-            if (!chain().findBlock(result.last_failed_block, nullptr /* block */, nullptr /* time */, &time_max)) {
-                throw std::logic_error("ScanForWalletTransactions returned invalid block hash");
-            }
+            CHECK_NONFATAL(chain().findBlock(result.last_failed_block, FoundBlock().maxTime(time_max)));
             return time_max + TIMESTAMP_WINDOW + 1;
         }
     }
@@ -1671,7 +1672,7 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
         }
 
         CBlock block;
-        if (chain().findBlock(block_hash, &block) && !block.IsNull()) {
+        if (chain().findBlock(block_hash, FoundBlock().data(block)) && !block.IsNull()) {
             auto locked_chain = chain().lock();
             LOCK(cs_wallet);
             if (!locked_chain->getBlockHeight(block_hash)) {
@@ -3622,7 +3623,7 @@ unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx) const
     unsigned int nTimeSmart = wtx.nTimeReceived;
     if (!wtx.isUnconfirmed() && !wtx.isAbandoned()) {
         int64_t blocktime;
-        if (chain().findBlock(wtx.m_confirm.hashBlock, nullptr /* block */, &blocktime)) {
+        if (chain().findBlock(wtx.m_confirm.hashBlock, FoundBlock().time(blocktime))) {
             int64_t latestNow = wtx.nTimeReceived;
             int64_t latestEntry = 0;
 

From f6da44ccce4cfff53433e665305a6fe0a01364e4 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Thu, 16 Jan 2020 15:56:58 -0500
Subject: [PATCH 02/12] wallet: Avoid use of Chain::Lock in tryGetTxStatus and
 tryGetBalances

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

It also helps ensure the GUI display stays up to date in the case where the
node chain height runs ahead of wallet last block processed height.
---
 src/interfaces/wallet.cpp | 17 +++++++----------
 src/wallet/wallet.h       |  6 ++++++
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index 645a8709d..c67b82643 100644
--- a/src/interfaces/wallet.cpp
+++ b/src/interfaces/wallet.cpp
@@ -14,6 +14,7 @@
 #include <sync.h>
 #include <ui_interface.h>
 #include <uint256.h>
+#include <util/check.h>
 #include <util/system.h>
 #include <wallet/feebumper.h>
 #include <wallet/fees.h>
@@ -62,7 +63,7 @@ WalletTx MakeWalletTx(CWallet& wallet, const CWalletTx& wtx)
 WalletTxStatus MakeWalletTxStatus(interfaces::Chain::Lock& locked_chain, const CWalletTx& wtx)
 {
     WalletTxStatus result;
-    result.block_height = locked_chain.getBlockHeight(wtx.m_confirm.hashBlock).get_value_or(std::numeric_limits<int>::max());
+    result.block_height = wtx.m_confirm.block_height > 0 ? wtx.m_confirm.block_height : std::numeric_limits<int>::max();
     result.blocks_to_maturity = wtx.GetBlocksToMaturity();
     result.depth_in_main_chain = wtx.GetDepthInMainChain();
     result.time_received = wtx.nTimeReceived;
@@ -317,13 +318,9 @@ public:
         if (mi == m_wallet->mapWallet.end()) {
             return false;
         }
-        if (Optional<int> height = locked_chain->getHeight()) {
-            num_blocks = *height;
-            block_time = locked_chain->getBlockTime(*height);
-        } else {
-            num_blocks = -1;
-            block_time = -1;
-        }
+        num_blocks = m_wallet->GetLastBlockHeight();
+        block_time = -1;
+        CHECK_NONFATAL(m_wallet->chain().findBlock(m_wallet->GetLastBlockHash(), FoundBlock().time(block_time)));
         tx_status = MakeWalletTxStatus(*locked_chain, mi->second);
         return true;
     }
@@ -372,12 +369,12 @@ public:
     {
         auto locked_chain = m_wallet->chain().lock(true /* try_lock */);
         if (!locked_chain) return false;
-        num_blocks = locked_chain->getHeight().get_value_or(-1);
-        if (!force && num_blocks == cached_num_blocks) return false;
         TRY_LOCK(m_wallet->cs_wallet, locked_wallet);
         if (!locked_wallet) {
             return false;
         }
+        num_blocks = m_wallet->GetLastBlockHeight();
+        if (!force && num_blocks == cached_num_blocks) return false;
         balances = getBalances();
         return true;
     }
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index fe5977348..26824946c 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -1200,6 +1200,12 @@ public:
         assert(m_last_block_processed_height >= 0);
         return m_last_block_processed_height;
     };
+    uint256 GetLastBlockHash() const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet)
+    {
+        AssertLockHeld(cs_wallet);
+        assert(m_last_block_processed_height >= 0);
+        return m_last_block_processed;
+    }
     /** Set last block processed height, currently only use in unit test */
     void SetLastBlockProcessed(int block_height, uint256 block_hash) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet)
     {

From ade5f87971211bc67753f14a0d49e020142efc7c Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Thu, 16 Jan 2020 16:13:15 -0500
Subject: [PATCH 03/12] wallet refactor: Avoid use of Chain::Lock in qt
 wallettests

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change doesn't affect behavior.
---
 src/qt/test/wallettests.cpp | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/src/qt/test/wallettests.cpp b/src/qt/test/wallettests.cpp
index c1a0f63f7..6a136ba74 100644
--- a/src/qt/test/wallettests.cpp
+++ b/src/qt/test/wallettests.cpp
@@ -151,12 +151,9 @@ void TestGUI(interfaces::Node& node)
         wallet->SetLastBlockProcessed(105, ::ChainActive().Tip()->GetBlockHash());
     }
     {
-        auto locked_chain = wallet->chain().lock();
-        LockAssertion lock(::cs_main);
-
         WalletRescanReserver reserver(wallet.get());
         reserver.reserve();
-        CWallet::ScanResult result = wallet->ScanForWalletTransactions(locked_chain->getBlockHash(0), {} /* stop_block */, reserver, true /* fUpdate */);
+        CWallet::ScanResult result = wallet->ScanForWalletTransactions(Params().GetConsensus().hashGenesisBlock, {} /* stop_block */, reserver, true /* fUpdate */);
         QCOMPARE(result.status, CWallet::ScanResult::SUCCESS);
         QCOMPARE(result.last_scanned_block, ::ChainActive().Tip()->GetBlockHash());
         QVERIFY(result.last_failed_block.IsNull());

From c1694ce6bb7e19a8722d5583cd85ad17da40bb67 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Thu, 16 Jan 2020 16:38:30 -0500
Subject: [PATCH 04/12] wallet: Avoid use of Chain::Lock in importprunedfunds

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip, in which case the "Block not found in chain" error
will be stricter and not allow importing data from a blocks between the wallet
last processed tip and the current node tip.
---
 src/interfaces/chain.cpp      |  8 ++++++++
 src/interfaces/chain.h        |  6 ++++++
 src/test/interfaces_tests.cpp | 10 ++++++++++
 src/wallet/rpcdump.cpp        | 11 ++++++-----
 4 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index cfaf79f70..1c1fbe738 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -267,6 +267,14 @@ public:
         WAIT_LOCK(cs_main, lock);
         return FillBlock(LookupBlockIndex(hash), block, lock);
     }
+    bool findAncestorByHash(const uint256& block_hash, const uint256& ancestor_hash, const FoundBlock& ancestor_out) override
+    {
+        WAIT_LOCK(cs_main, lock);
+        const CBlockIndex* block = LookupBlockIndex(block_hash);
+        const CBlockIndex* ancestor = LookupBlockIndex(ancestor_hash);
+        if (block && ancestor && block->GetAncestor(ancestor->nHeight) != ancestor) ancestor = nullptr;
+        return FillBlock(ancestor, ancestor_out, lock);
+    }
     void findCoins(std::map<COutPoint, Coin>& coins) override { return FindCoins(m_node, coins); }
     double guessVerificationProgress(const uint256& block_hash) override
     {
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 3778ab9a8..7504f4cfb 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -150,6 +150,12 @@ public:
     //! or contents.
     virtual bool findBlock(const uint256& hash, const FoundBlock& block={}) = 0;
 
+    //! Return whether block descends from a specified ancestor, and
+    //! optionally return ancestor information.
+    virtual bool findAncestorByHash(const uint256& block_hash,
+        const uint256& ancestor_hash,
+        const FoundBlock& ancestor_out={}) = 0;
+
     //! Look up unspent output information. Returns coins in the mempool and in
     //! the current chain UTXO set. Iterates through all the keys in the map and
     //! populates the values.
diff --git a/src/test/interfaces_tests.cpp b/src/test/interfaces_tests.cpp
index e3d1738c7..caa988df0 100644
--- a/src/test/interfaces_tests.cpp
+++ b/src/test/interfaces_tests.cpp
@@ -44,4 +44,14 @@ BOOST_AUTO_TEST_CASE(findBlock)
     BOOST_CHECK(!chain->findBlock({}, FoundBlock()));
 }
 
+BOOST_AUTO_TEST_CASE(findAncestorByHash)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+    int height = -1;
+    BOOST_CHECK(chain->findAncestorByHash(active[20]->GetBlockHash(), active[10]->GetBlockHash(), FoundBlock().height(height)));
+    BOOST_CHECK_EQUAL(height, 10);
+    BOOST_CHECK(!chain->findAncestorByHash(active[10]->GetBlockHash(), active[20]->GetBlockHash()));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index e4d0a3fa6..1d6b4832e 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -28,6 +28,8 @@
 
 
 
+using interfaces::FoundBlock;
+
 std::string static EncodeDumpString(const std::string &str) {
     std::stringstream ret;
     for (const unsigned char c : str) {
@@ -359,8 +361,9 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
     }
 
     auto locked_chain = pwallet->chain().lock();
-    Optional<int> height = locked_chain->getBlockHeight(merkleBlock.header.GetHash());
-    if (height == nullopt) {
+    LOCK(pwallet->cs_wallet);
+    int height;
+    if (!pwallet->chain().findAncestorByHash(pwallet->GetLastBlockHash(), merkleBlock.header.GetHash(), FoundBlock().height(height))) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
     }
 
@@ -371,11 +374,9 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
 
     unsigned int txnIndex = vIndex[it - vMatch.begin()];
 
-    CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, *height, merkleBlock.header.GetHash(), txnIndex);
+    CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, height, merkleBlock.header.GetHash(), txnIndex);
     wtx.m_confirm = confirm;
 
-    LOCK(pwallet->cs_wallet);
-
     if (pwallet->IsMine(*wtx.tx)) {
         pwallet->AddToWallet(wtx, false);
         return NullUniValue;

From 25a9fcf9e53bfa94e8f8b19a4abfda0f444f6b2a Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Thu, 16 Jan 2020 16:42:01 -0500
Subject: [PATCH 05/12] wallet: Avoid use of Chain::Lock in importwallet and
 dumpwallet

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip, in which case it will use more accurate backup and
rescan timestamps.
---
 src/wallet/rpcdump.cpp           | 10 +++++-----
 src/wallet/test/wallet_tests.cpp |  4 +++-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 1d6b4832e..255255c3f 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -566,8 +566,7 @@ UniValue importwallet(const JSONRPCRequest& request)
         if (!file.is_open()) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
         }
-        Optional<int> tip_height = locked_chain->getHeight();
-        nTimeBegin = tip_height ? locked_chain->getBlockTime(*tip_height) : 0;
+        CHECK_NONFATAL(pwallet->chain().findBlock(pwallet->GetLastBlockHash(), FoundBlock().time(nTimeBegin)));
 
         int64_t nFilesize = std::max((int64_t)1, (int64_t)file.tellg());
         file.seekg(0, file.beg);
@@ -791,9 +790,10 @@ UniValue dumpwallet(const JSONRPCRequest& request)
     // produce output
     file << strprintf("# Wallet dump created by Bitcoin %s\n", CLIENT_BUILD);
     file << strprintf("# * Created on %s\n", FormatISO8601DateTime(GetTime()));
-    const Optional<int> tip_height = locked_chain->getHeight();
-    file << strprintf("# * Best block at time of backup was %i (%s),\n", tip_height.get_value_or(-1), tip_height ? locked_chain->getBlockHash(*tip_height).ToString() : "(missing block hash)");
-    file << strprintf("#   mined on %s\n", tip_height ? FormatISO8601DateTime(locked_chain->getBlockTime(*tip_height)) : "(missing block time)");
+    file << strprintf("# * Best block at time of backup was %i (%s),\n", pwallet->GetLastBlockHeight(), pwallet->GetLastBlockHash().ToString());
+    int64_t block_time = 0;
+    CHECK_NONFATAL(pwallet->chain().findBlock(pwallet->GetLastBlockHash(), FoundBlock().time(block_time)));
+    file << strprintf("#   mined on %s\n", FormatISO8601DateTime(block_time));
     file << "\n";
 
     // add the base58check encoded extended master if the wallet uses HD
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index a487e9e2e..f333b09ad 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -225,6 +225,7 @@ BOOST_FIXTURE_TEST_CASE(importwallet_rescan, TestChain100Setup)
         request.params.setArray();
         request.params.push_back(backup_file);
         AddWallet(wallet);
+        wallet->SetLastBlockProcessed(::ChainActive().Height(), ::ChainActive().Tip()->GetBlockHash());
         ::dumpwallet(request);
         RemoveWallet(wallet);
     }
@@ -233,16 +234,17 @@ BOOST_FIXTURE_TEST_CASE(importwallet_rescan, TestChain100Setup)
     // were scanned, and no prior blocks were scanned.
     {
         std::shared_ptr<CWallet> wallet = std::make_shared<CWallet>(chain.get(), WalletLocation(), WalletDatabase::CreateDummy());
+        LOCK(wallet->cs_wallet);
         wallet->SetupLegacyScriptPubKeyMan();
 
         JSONRPCRequest request;
         request.params.setArray();
         request.params.push_back(backup_file);
         AddWallet(wallet);
+        wallet->SetLastBlockProcessed(::ChainActive().Height(), ::ChainActive().Tip()->GetBlockHash());
         ::importwallet(request);
         RemoveWallet(wallet);
 
-        LOCK(wallet->cs_wallet);
         BOOST_CHECK_EQUAL(wallet->mapWallet.size(), 3U);
         BOOST_CHECK_EQUAL(m_coinbase_txns.size(), 103U);
         for (size_t i = 0; i < m_coinbase_txns.size(); ++i) {

From bc96a9bfc61afdb696fb92cb644ed5fc3d1793f1 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Thu, 16 Jan 2020 16:47:00 -0500
Subject: [PATCH 06/12] wallet: Avoid use of Chain::Lock in importmulti

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip, in which case it may use a more accurate rescan
time.
---
 src/interfaces/chain.cpp         | 7 -------
 src/interfaces/chain.h           | 4 ----
 src/wallet/rpcdump.cpp           | 9 +--------
 src/wallet/test/wallet_tests.cpp | 1 +
 4 files changed, 2 insertions(+), 19 deletions(-)

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 1c1fbe738..dbc49eca1 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -87,13 +87,6 @@ class LockImpl : public Chain::Lock, public UniqueLock<RecursiveMutex>
         assert(block != nullptr);
         return block->GetBlockTime();
     }
-    int64_t getBlockMedianTimePast(int height) override
-    {
-        LockAssertion lock(::cs_main);
-        CBlockIndex* block = ::ChainActive()[height];
-        assert(block != nullptr);
-        return block->GetMedianTimePast();
-    }
     bool haveBlockOnDisk(int height) override
     {
         LockAssertion lock(::cs_main);
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 7504f4cfb..4c711a618 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -103,10 +103,6 @@ public:
         //! Get block time. Height must be valid or this function will abort.
         virtual int64_t getBlockTime(int height) = 0;
 
-        //! Get block median time past. Height must be valid or this function
-        //! will abort.
-        virtual int64_t getBlockMedianTimePast(int height) = 0;
-
         //! Check that the block is available on disk (i.e. has not been
         //! pruned), and contains transactions.
         virtual bool haveBlockOnDisk(int height) = 0;
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 255255c3f..c77559c63 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -1379,20 +1379,13 @@ UniValue importmulti(const JSONRPCRequest& mainRequest)
         EnsureWalletIsUnlocked(pwallet);
 
         // Verify all timestamps are present before importing any keys.
-        const Optional<int> tip_height = locked_chain->getHeight();
-        now = tip_height ? locked_chain->getBlockMedianTimePast(*tip_height) : 0;
+        CHECK_NONFATAL(pwallet->chain().findBlock(pwallet->GetLastBlockHash(), FoundBlock().time(nLowestTimestamp).mtpTime(now)));
         for (const UniValue& data : requests.getValues()) {
             GetImportTimestamp(data, now);
         }
 
         const int64_t minimumTimestamp = 1;
 
-        if (fRescan && tip_height) {
-            nLowestTimestamp = locked_chain->getBlockTime(*tip_height);
-        } else {
-            fRescan = false;
-        }
-
         for (const UniValue& data : requests.getValues()) {
             const int64_t timestamp = std::max(GetImportTimestamp(data, now), minimumTimestamp);
             const UniValue result = ProcessImport(pwallet, data, timestamp);
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index f333b09ad..fb5b0587d 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -152,6 +152,7 @@ BOOST_FIXTURE_TEST_CASE(importmulti_rescan, TestChain100Setup)
     {
         std::shared_ptr<CWallet> wallet = std::make_shared<CWallet>(chain.get(), WalletLocation(), WalletDatabase::CreateDummy());
         wallet->SetupLegacyScriptPubKeyMan();
+        WITH_LOCK(wallet->cs_wallet, wallet->SetLastBlockProcessed(newTip->nHeight, newTip->GetBlockHash()));
         AddWallet(wallet);
         UniValue keys;
         keys.setArray();

From f7ba881bc669451a60fedac58a449794702a3e23 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Tue, 21 Jan 2020 15:00:33 -0500
Subject: [PATCH 07/12] wallet: Avoid use of Chain::Lock in listsinceblock

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip. Previously listsinceblock might not have returned
all transactions up to the claimed "lastblock" value in this case, resulting in
race conditions and potentially missing transactions in cases where
listsinceblock was called in a loop like
https://github.com/bitcoin/bitcoin/issues/14338#issuecomment-426706574
---
 src/interfaces/chain.cpp      | 18 +++++++++++++++++
 src/interfaces/chain.h        | 12 ++++++++++++
 src/test/interfaces_tests.cpp | 37 +++++++++++++++++++++++++++++++++++
 src/wallet/rpcwallet.cpp      | 12 ++++++------
 4 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index dbc49eca1..8cd4ab0b6 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -260,6 +260,16 @@ public:
         WAIT_LOCK(cs_main, lock);
         return FillBlock(LookupBlockIndex(hash), block, lock);
     }
+    bool findAncestorByHeight(const uint256& block_hash, int ancestor_height, const FoundBlock& ancestor_out) override
+    {
+        WAIT_LOCK(cs_main, lock);
+        if (const CBlockIndex* block = LookupBlockIndex(block_hash)) {
+            if (const CBlockIndex* ancestor = block->GetAncestor(ancestor_height)) {
+                return FillBlock(ancestor, ancestor_out, lock);
+            }
+        }
+        return FillBlock(nullptr, ancestor_out, lock);
+    }
     bool findAncestorByHash(const uint256& block_hash, const uint256& ancestor_hash, const FoundBlock& ancestor_out) override
     {
         WAIT_LOCK(cs_main, lock);
@@ -268,6 +278,14 @@ public:
         if (block && ancestor && block->GetAncestor(ancestor->nHeight) != ancestor) ancestor = nullptr;
         return FillBlock(ancestor, ancestor_out, lock);
     }
+    bool findCommonAncestor(const uint256& block_hash1, const uint256& block_hash2, const FoundBlock& ancestor_out, const FoundBlock& block1_out, const FoundBlock& block2_out) override
+    {
+        WAIT_LOCK(cs_main, lock);
+        const CBlockIndex* block1 = LookupBlockIndex(block_hash1);
+        const CBlockIndex* block2 = LookupBlockIndex(block_hash2);
+        const CBlockIndex* ancestor = block1 && block2 ? LastCommonAncestor(block1, block2) : nullptr;
+        return FillBlock(ancestor, ancestor_out, lock) & FillBlock(block1, block1_out, lock) & FillBlock(block2, block2_out, lock);
+    }
     void findCoins(std::map<COutPoint, Coin>& coins) override { return FindCoins(m_node, coins); }
     double guessVerificationProgress(const uint256& block_hash) override
     {
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 4c711a618..ee79b3e6d 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -146,12 +146,24 @@ public:
     //! or contents.
     virtual bool findBlock(const uint256& hash, const FoundBlock& block={}) = 0;
 
+    //! Find ancestor of block at specified height and optionally return
+    //! ancestor information.
+    virtual bool findAncestorByHeight(const uint256& block_hash, int ancestor_height, const FoundBlock& ancestor_out={}) = 0;
+
     //! Return whether block descends from a specified ancestor, and
     //! optionally return ancestor information.
     virtual bool findAncestorByHash(const uint256& block_hash,
         const uint256& ancestor_hash,
         const FoundBlock& ancestor_out={}) = 0;
 
+    //! Find most recent common ancestor between two blocks and optionally
+    //! return block information.
+    virtual bool findCommonAncestor(const uint256& block_hash1,
+        const uint256& block_hash2,
+        const FoundBlock& ancestor_out={},
+        const FoundBlock& block1_out={},
+        const FoundBlock& block2_out={}) = 0;
+
     //! Look up unspent output information. Returns coins in the mempool and in
     //! the current chain UTXO set. Iterates through all the keys in the map and
     //! populates the values.
diff --git a/src/test/interfaces_tests.cpp b/src/test/interfaces_tests.cpp
index caa988df0..f95743ec4 100644
--- a/src/test/interfaces_tests.cpp
+++ b/src/test/interfaces_tests.cpp
@@ -2,7 +2,10 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <chainparams.h>
+#include <consensus/validation.h>
 #include <interfaces/chain.h>
+#include <script/standard.h>
 #include <test/util/setup_common.h>
 #include <validation.h>
 
@@ -44,6 +47,16 @@ BOOST_AUTO_TEST_CASE(findBlock)
     BOOST_CHECK(!chain->findBlock({}, FoundBlock()));
 }
 
+BOOST_AUTO_TEST_CASE(findAncestorByHeight)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+    uint256 hash;
+    BOOST_CHECK(chain->findAncestorByHeight(active[20]->GetBlockHash(), 10, FoundBlock().hash(hash)));
+    BOOST_CHECK_EQUAL(hash, active[10]->GetBlockHash());
+    BOOST_CHECK(!chain->findAncestorByHeight(active[10]->GetBlockHash(), 20));
+}
+
 BOOST_AUTO_TEST_CASE(findAncestorByHash)
 {
     auto chain = interfaces::MakeChain(m_node);
@@ -54,4 +67,28 @@ BOOST_AUTO_TEST_CASE(findAncestorByHash)
     BOOST_CHECK(!chain->findAncestorByHash(active[10]->GetBlockHash(), active[20]->GetBlockHash()));
 }
 
+BOOST_AUTO_TEST_CASE(findCommonAncestor)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+    auto* orig_tip = active.Tip();
+    for (int i = 0; i < 10; ++i) {
+        BlockValidationState state;
+        ChainstateActive().InvalidateBlock(state, Params(), active.Tip());
+    }
+    BOOST_CHECK_EQUAL(active.Height(), orig_tip->nHeight - 10);
+    coinbaseKey.MakeNewKey(true);
+    for (int i = 0; i < 20; ++i) {
+        CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey()));
+    }
+    BOOST_CHECK_EQUAL(active.Height(), orig_tip->nHeight + 10);
+    uint256 fork_hash;
+    int fork_height;
+    int orig_height;
+    BOOST_CHECK(chain->findCommonAncestor(orig_tip->GetBlockHash(), active.Tip()->GetBlockHash(), FoundBlock().height(fork_height).hash(fork_hash), FoundBlock().height(orig_height)));
+    BOOST_CHECK_EQUAL(orig_height, orig_tip->nHeight);
+    BOOST_CHECK_EQUAL(fork_height, orig_tip->nHeight - 10);
+    BOOST_CHECK_EQUAL(fork_hash, active[fork_height]->GetBlockHash());
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 1e6d37c46..14e2066c9 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -1581,8 +1581,9 @@ static UniValue listsinceblock(const JSONRPCRequest& request)
     uint256 blockId;
     if (!request.params[0].isNull() && !request.params[0].get_str().empty()) {
         blockId = ParseHashV(request.params[0], "blockhash");
-        height = locked_chain->findFork(blockId, &altheight);
-        if (!height) {
+        height.emplace();
+        altheight.emplace();
+        if (!pwallet->chain().findCommonAncestor(blockId, pwallet->GetLastBlockHash(), /* ancestor out */ FoundBlock().height(*height), /* blockId out */ FoundBlock().height(*altheight))) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
     }
@@ -1601,8 +1602,7 @@ static UniValue listsinceblock(const JSONRPCRequest& request)
 
     bool include_removed = (request.params[3].isNull() || request.params[3].get_bool());
 
-    const Optional<int> tip_height = locked_chain->getHeight();
-    int depth = tip_height && height ? (1 + *tip_height - *height) : -1;
+    int depth = height ? pwallet->GetLastBlockHeight() + 1 - *height : -1;
 
     UniValue transactions(UniValue::VARR);
 
@@ -1634,8 +1634,8 @@ static UniValue listsinceblock(const JSONRPCRequest& request)
         --*altheight;
     }
 
-    int last_height = tip_height ? *tip_height + 1 - target_confirms : -1;
-    uint256 lastblock = last_height >= 0 ? locked_chain->getBlockHash(last_height) : uint256();
+    uint256 lastblock;
+    CHECK_NONFATAL(pwallet->chain().findAncestorByHeight(pwallet->GetLastBlockHash(), pwallet->GetLastBlockHeight() + 1 - target_confirms, FoundBlock().hash(lastblock)));
 
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("transactions", transactions);

From 3cb85ac594f115db99f96b0a0f4bfdcd69ef0590 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Tue, 21 Jan 2020 15:55:19 -0500
Subject: [PATCH 08/12] wallet refactor: Avoid use of Chain::Lock in
 CWallet::RescanFromTime

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change has no effect on behavior.
---
 src/interfaces/chain.cpp      |  5 +++++
 src/interfaces/chain.h        |  6 ++++++
 src/test/interfaces_tests.cpp | 12 ++++++++++++
 src/wallet/wallet.cpp         | 11 ++++-------
 4 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 8cd4ab0b6..0d69c33be 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -260,6 +260,11 @@ public:
         WAIT_LOCK(cs_main, lock);
         return FillBlock(LookupBlockIndex(hash), block, lock);
     }
+    bool findFirstBlockWithTimeAndHeight(int64_t min_time, int min_height, const FoundBlock& block) override
+    {
+        WAIT_LOCK(cs_main, lock);
+        return FillBlock(ChainActive().FindEarliestAtLeast(min_time, min_height), block, lock);
+    }
     bool findAncestorByHeight(const uint256& block_hash, int ancestor_height, const FoundBlock& ancestor_out) override
     {
         WAIT_LOCK(cs_main, lock);
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index ee79b3e6d..16753b7cc 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -146,6 +146,12 @@ public:
     //! or contents.
     virtual bool findBlock(const uint256& hash, const FoundBlock& block={}) = 0;
 
+    //! Find first block in the chain with timestamp >= the given time
+    //! and height >= than the given height, return false if there is no block
+    //! with a high enough timestamp and height. Optionally return block
+    //! information.
+    virtual bool findFirstBlockWithTimeAndHeight(int64_t min_time, int min_height, const FoundBlock& block={}) = 0;
+
     //! Find ancestor of block at specified height and optionally return
     //! ancestor information.
     virtual bool findAncestorByHeight(const uint256& block_hash, int ancestor_height, const FoundBlock& ancestor_out={}) = 0;
diff --git a/src/test/interfaces_tests.cpp b/src/test/interfaces_tests.cpp
index f95743ec4..b398b5819 100644
--- a/src/test/interfaces_tests.cpp
+++ b/src/test/interfaces_tests.cpp
@@ -47,6 +47,18 @@ BOOST_AUTO_TEST_CASE(findBlock)
     BOOST_CHECK(!chain->findBlock({}, FoundBlock()));
 }
 
+BOOST_AUTO_TEST_CASE(findFirstBlockWithTimeAndHeight)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+    uint256 hash;
+    int height;
+    BOOST_CHECK(chain->findFirstBlockWithTimeAndHeight(/* min_time= */ 0, /* min_height= */ 5, FoundBlock().hash(hash).height(height)));
+    BOOST_CHECK_EQUAL(hash, active[5]->GetBlockHash());
+    BOOST_CHECK_EQUAL(height, 5);
+    BOOST_CHECK(!chain->findFirstBlockWithTimeAndHeight(/* min_time= */ active.Tip()->GetBlockTimeMax() + 1, /* min_height= */ 0));
+}
+
 BOOST_AUTO_TEST_CASE(findAncestorByHeight)
 {
     auto chain = interfaces::MakeChain(m_node);
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index c8641b03f..9ffb810ee 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1591,15 +1591,12 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
     // Find starting block. May be null if nCreateTime is greater than the
     // highest blockchain timestamp, in which case there is nothing that needs
     // to be scanned.
+    int start_height = 0;
     uint256 start_block;
-    {
-        auto locked_chain = chain().lock();
-        const Optional<int> start_height = locked_chain->findFirstBlockWithTimeAndHeight(startTime - TIMESTAMP_WINDOW, 0, &start_block);
-        const Optional<int> tip_height = locked_chain->getHeight();
-        WalletLogPrintf("%s: Rescanning last %i blocks\n", __func__, tip_height && start_height ? *tip_height - *start_height + 1 : 0);
-    }
+    bool start = chain().findFirstBlockWithTimeAndHeight(startTime - TIMESTAMP_WINDOW, 0, FoundBlock().hash(start_block).height(start_height));
+    WalletLogPrintf("%s: Rescanning last %i blocks\n", __func__, start ? WITH_LOCK(cs_wallet, return GetLastBlockHeight()) - start_height + 1 : 0);
 
-    if (!start_block.IsNull()) {
+    if (start) {
         // TODO: this should take into account failure by ScanResult::USER_ABORT
         ScanResult result = ScanForWalletTransactions(start_block, {} /* stop_block */, reserver, update);
         if (result.status == ScanResult::FAILURE) {

From 1be8ff280c78c30baabae9429c53c0bebb89c44d Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Tue, 21 Jan 2020 17:08:12 -0500
Subject: [PATCH 09/12] wallet: Avoid use of Chain::Lock in rescanblockchain

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip. The rescanblockchain error height error checking
will just be stricter in this case and only accept values up to the last
processed height
---
 src/interfaces/chain.cpp      | 33 ++++++++++++++++++--------------
 src/interfaces/chain.h        |  9 +++++----
 src/test/interfaces_tests.cpp | 36 +++++++++++++++++++++++++++++++++++
 src/wallet/rpcwallet.cpp      | 27 +++++++++-----------------
 src/wallet/wallet.cpp         | 15 ++++++++-------
 src/wallet/wallet.h           |  2 +-
 6 files changed, 78 insertions(+), 44 deletions(-)

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 0d69c33be..1c578b56c 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -103,20 +103,6 @@ class LockImpl : public Chain::Lock, public UniqueLock<RecursiveMutex>
         }
         return nullopt;
     }
-    Optional<int> findPruned(int start_height, Optional<int> stop_height) override
-    {
-        LockAssertion lock(::cs_main);
-        if (::fPruneMode) {
-            CBlockIndex* block = stop_height ? ::ChainActive()[*stop_height] : ::ChainActive().Tip();
-            while (block && block->nHeight >= start_height) {
-                if ((block->nStatus & BLOCK_HAVE_DATA) == 0) {
-                    return block->nHeight;
-                }
-                block = block->pprev;
-            }
-        }
-        return nullopt;
-    }
     Optional<int> findFork(const uint256& hash, Optional<int>* height) override
     {
         LockAssertion lock(::cs_main);
@@ -297,6 +283,25 @@ public:
         LOCK(cs_main);
         return GuessVerificationProgress(Params().TxData(), LookupBlockIndex(block_hash));
     }
+    bool hasBlocks(const uint256& block_hash, int min_height, Optional<int> max_height) override
+    {
+        // hasBlocks returns true if all ancestors of block_hash in specified
+        // range have block data (are not pruned), false if any ancestors in
+        // specified range are missing data.
+        //
+        // For simplicity and robustness, min_height and max_height are only
+        // used to limit the range, and passing min_height that's too low or
+        // max_height that's too high will not crash or change the result.
+        LOCK(::cs_main);
+        if (CBlockIndex* block = LookupBlockIndex(block_hash)) {
+            if (max_height && block->nHeight >= *max_height) block = block->GetAncestor(*max_height);
+            for (; block->nStatus & BLOCK_HAVE_DATA; block = block->pprev) {
+                // Check pprev to not segfault if min_height is too low
+                if (block->nHeight <= min_height || !block->pprev) return true;
+            }
+        }
+        return false;
+    }
     RBFTransactionState isRBFOptIn(const CTransaction& tx) override
     {
         LOCK(::mempool.cs);
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 16753b7cc..8bc0ed824 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -114,10 +114,6 @@ public:
         //! (to avoid the cost of a second lookup in case this information is needed.)
         virtual Optional<int> findFirstBlockWithTimeAndHeight(int64_t time, int height, uint256* hash) = 0;
 
-        //! Return height of last block in the specified range which is pruned, or
-        //! nullopt if no block in the range is pruned. Range is inclusive.
-        virtual Optional<int> findPruned(int start_height = 0, Optional<int> stop_height = nullopt) = 0;
-
         //! Return height of the specified block if it is on the chain, otherwise
         //! return the height of the highest block on chain that's an ancestor
         //! of the specified block, or nullopt if there is no common ancestor.
@@ -179,6 +175,11 @@ public:
     //! the specified block hash are verified.
     virtual double guessVerificationProgress(const uint256& block_hash) = 0;
 
+    //! Return true if data is available for all blocks in the specified range
+    //! of blocks. This checks all blocks that are ancestors of block_hash in
+    //! the height range from min_height to max_height, inclusive.
+    virtual bool hasBlocks(const uint256& block_hash, int min_height = 0, Optional<int> max_height = {}) = 0;
+
     //! Check if transaction is RBF opt in.
     virtual RBFTransactionState isRBFOptIn(const CTransaction& tx) = 0;
 
diff --git a/src/test/interfaces_tests.cpp b/src/test/interfaces_tests.cpp
index b398b5819..5fba0e042 100644
--- a/src/test/interfaces_tests.cpp
+++ b/src/test/interfaces_tests.cpp
@@ -103,4 +103,40 @@ BOOST_AUTO_TEST_CASE(findCommonAncestor)
     BOOST_CHECK_EQUAL(fork_hash, active[fork_height]->GetBlockHash());
 }
 
+BOOST_AUTO_TEST_CASE(hasBlocks)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+
+    // Test ranges
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 10, 90));
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 10, {}));
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 0, 90));
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 0, {}));
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), -1000, 1000));
+    active[5]->nStatus &= ~BLOCK_HAVE_DATA;
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 10, 90));
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 10, {}));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 0, 90));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 0, {}));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), -1000, 1000));
+    active[95]->nStatus &= ~BLOCK_HAVE_DATA;
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 10, 90));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 10, {}));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 0, 90));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 0, {}));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), -1000, 1000));
+    active[50]->nStatus &= ~BLOCK_HAVE_DATA;
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 10, 90));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 10, {}));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 0, 90));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 0, {}));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), -1000, 1000));
+
+    // Test edge cases
+    BOOST_CHECK(chain->hasBlocks(active.Tip()->GetBlockHash(), 6, 49));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 5, 49));
+    BOOST_CHECK(!chain->hasBlocks(active.Tip()->GetBlockHash(), 6, 50));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 14e2066c9..6bda33c6c 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3536,22 +3536,23 @@ UniValue rescanblockchain(const JSONRPCRequest& request)
     }
 
     int start_height = 0;
-    uint256 start_block, stop_block;
+    Optional<int> stop_height;
+    uint256 start_block;
     {
         auto locked_chain = pwallet->chain().lock();
-        Optional<int> tip_height = locked_chain->getHeight();
+        LOCK(pwallet->cs_wallet);
+        int tip_height = pwallet->GetLastBlockHeight();
 
         if (!request.params[0].isNull()) {
             start_height = request.params[0].get_int();
-            if (start_height < 0 || !tip_height || start_height > *tip_height) {
+            if (start_height < 0 || start_height > tip_height) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid start_height");
             }
         }
 
-        Optional<int> stop_height;
         if (!request.params[1].isNull()) {
             stop_height = request.params[1].get_int();
-            if (*stop_height < 0 || !tip_height || *stop_height > *tip_height) {
+            if (*stop_height < 0 || *stop_height > tip_height) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid stop_height");
             }
             else if (*stop_height < start_height) {
@@ -3560,25 +3561,15 @@ UniValue rescanblockchain(const JSONRPCRequest& request)
         }
 
         // We can't rescan beyond non-pruned blocks, stop and throw an error
-        if (locked_chain->findPruned(start_height, stop_height)) {
+        if (!pwallet->chain().hasBlocks(pwallet->GetLastBlockHash(), start_height, stop_height)) {
             throw JSONRPCError(RPC_MISC_ERROR, "Can't rescan beyond pruned data. Use RPC call getblockchaininfo to determine your pruned height.");
         }
 
-        if (tip_height) {
-            start_block = locked_chain->getBlockHash(start_height);
-            // If called with a stop_height, set the stop_height here to
-            // trigger a rescan to that height.
-            // If called without a stop height, leave stop_height as null here
-            // so rescan continues to the tip (even if the tip advances during
-            // rescan).
-            if (stop_height) {
-                stop_block = locked_chain->getBlockHash(*stop_height);
-            }
-        }
+        CHECK_NONFATAL(pwallet->chain().findAncestorByHeight(pwallet->GetLastBlockHash(), start_height, FoundBlock().hash(start_block)));
     }
 
     CWallet::ScanResult result =
-        pwallet->ScanForWalletTransactions(start_block, stop_block, reserver, true /* fUpdate */);
+        pwallet->ScanForWalletTransactions(start_block, stop_height, reserver, true /* fUpdate */);
     switch (result.status) {
     case CWallet::ScanResult::SUCCESS:
         break;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 9ffb810ee..70d39a8fc 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1615,9 +1615,8 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
  *
  * @param[in] start_block Scan starting block. If block is not on the active
  *                        chain, the scan will return SUCCESS immediately.
- * @param[in] stop_block  Scan ending block. If block is not on the active
- *                        chain, the scan will continue until it reaches the
- *                        chain tip.
+ * @param[in] max_height  Optional max scanning height. If unset there is
+ *                        no maximum and scanning can continue to the tip
  *
  * @return ScanResult returning scan information and indicating success or
  *         failure. Return status will be set to SUCCESS if scan was
@@ -1629,7 +1628,7 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
  * the main chain after to the addition of any new keys you want to detect
  * transactions for.
  */
-CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_block, const uint256& stop_block, const WalletRescanReserver& reserver, bool fUpdate)
+CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_block, Optional<int> max_height, const WalletRescanReserver& reserver, bool fUpdate)
 {
     int64_t nNow = GetTime();
     int64_t start_time = GetTimeMillis();
@@ -1654,8 +1653,10 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
             tip_hash = locked_chain->getBlockHash(*tip_height);
         }
         block_height = locked_chain->getBlockHeight(block_hash);
+        uint256 end_hash = tip_hash;
+        if (max_height) chain().findAncestorByHeight(tip_hash, *max_height, FoundBlock().hash(end_hash));
         progress_begin = chain().guessVerificationProgress(block_hash);
-        progress_end = chain().guessVerificationProgress(stop_block.IsNull() ? tip_hash : stop_block);
+        progress_end = chain().guessVerificationProgress(end_hash);
     }
     double progress_current = progress_begin;
     while (block_height && !fAbortRescan && !chain().shutdownRequested()) {
@@ -1693,7 +1694,7 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
             result.last_failed_block = block_hash;
             result.status = ScanResult::FAILURE;
         }
-        if (block_hash == stop_block) {
+        if (max_height && *block_height >= *max_height) {
             break;
         }
         {
@@ -1712,7 +1713,7 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
             // handle updated tip hash
             const uint256 prev_tip_hash = tip_hash;
             tip_hash = locked_chain->getBlockHash(*tip_height);
-            if (stop_block.IsNull() && prev_tip_hash != tip_hash) {
+            if (!max_height && prev_tip_hash != tip_hash) {
                 // in case the tip has changed, update progress max
                 progress_end = chain().guessVerificationProgress(tip_hash);
             }
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 26824946c..f105ccd17 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -894,7 +894,7 @@ public:
         //! USER_ABORT.
         uint256 last_failed_block;
     };
-    ScanResult ScanForWalletTransactions(const uint256& first_block, const uint256& last_block, const WalletRescanReserver& reserver, bool fUpdate);
+    ScanResult ScanForWalletTransactions(const uint256& first_block, Optional<int> max_height, const WalletRescanReserver& reserver, bool fUpdate);
     void transactionRemovedFromMempool(const CTransactionRef &ptx) override;
     void ReacceptWalletTransactions() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     void ResendWalletTransactions();

From c0d07dc4cba7634cde4e8bf586557772f3248a42 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Wed, 22 Jan 2020 16:53:42 -0500
Subject: [PATCH 10/12] wallet: Avoid use of Chain::Lock in
 CWallet::ScanForWalletTransactions

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change affects behavior in a few small ways.

- If there's no max_height specified, percentage progress is measured ending at
  wallet last processed block instead of node tip

- More consistent error reporting: Early check to see if start_block is on the
  active chain is removed, so start_block is always read and the triggers an
  error if it's unavailable
---
 src/interfaces/chain.cpp         |  7 ++++
 src/interfaces/chain.h           |  5 +++
 src/qt/test/wallettests.cpp      |  2 +-
 src/test/interfaces_tests.cpp    | 15 ++++++++
 src/wallet/rpcwallet.cpp         |  2 +-
 src/wallet/test/wallet_tests.cpp | 14 ++++----
 src/wallet/wallet.cpp            | 60 +++++++++++++++-----------------
 src/wallet/wallet.h              |  2 +-
 8 files changed, 65 insertions(+), 42 deletions(-)

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 1c578b56c..2b2d3a4b8 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -251,6 +251,13 @@ public:
         WAIT_LOCK(cs_main, lock);
         return FillBlock(ChainActive().FindEarliestAtLeast(min_time, min_height), block, lock);
     }
+    bool findNextBlock(const uint256& block_hash, int block_height, const FoundBlock& next, bool* reorg) override {
+        WAIT_LOCK(cs_main, lock);
+        CBlockIndex* block = ChainActive()[block_height];
+        if (block && block->GetBlockHash() != block_hash) block = nullptr;
+        if (reorg) *reorg = !block;
+        return FillBlock(block ? ChainActive()[block_height + 1] : nullptr, next, lock);
+    }
     bool findAncestorByHeight(const uint256& block_hash, int ancestor_height, const FoundBlock& ancestor_out) override
     {
         WAIT_LOCK(cs_main, lock);
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 8bc0ed824..ef5a002f5 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -148,6 +148,11 @@ public:
     //! information.
     virtual bool findFirstBlockWithTimeAndHeight(int64_t min_time, int min_height, const FoundBlock& block={}) = 0;
 
+    //! Find next block if block is part of current chain. Also flag if
+    //! there was a reorg and the specified block hash is no longer in the
+    //! current chain, and optionally return block information.
+    virtual bool findNextBlock(const uint256& block_hash, int block_height, const FoundBlock& next={}, bool* reorg=nullptr) = 0;
+
     //! Find ancestor of block at specified height and optionally return
     //! ancestor information.
     virtual bool findAncestorByHeight(const uint256& block_hash, int ancestor_height, const FoundBlock& ancestor_out={}) = 0;
diff --git a/src/qt/test/wallettests.cpp b/src/qt/test/wallettests.cpp
index 6a136ba74..c329d5d10 100644
--- a/src/qt/test/wallettests.cpp
+++ b/src/qt/test/wallettests.cpp
@@ -153,7 +153,7 @@ void TestGUI(interfaces::Node& node)
     {
         WalletRescanReserver reserver(wallet.get());
         reserver.reserve();
-        CWallet::ScanResult result = wallet->ScanForWalletTransactions(Params().GetConsensus().hashGenesisBlock, {} /* stop_block */, reserver, true /* fUpdate */);
+        CWallet::ScanResult result = wallet->ScanForWalletTransactions(Params().GetConsensus().hashGenesisBlock, 0 /* block height */, {} /* max height */, reserver, true /* fUpdate */);
         QCOMPARE(result.status, CWallet::ScanResult::SUCCESS);
         QCOMPARE(result.last_scanned_block, ::ChainActive().Tip()->GetBlockHash());
         QVERIFY(result.last_failed_block.IsNull());
diff --git a/src/test/interfaces_tests.cpp b/src/test/interfaces_tests.cpp
index 5fba0e042..fab357175 100644
--- a/src/test/interfaces_tests.cpp
+++ b/src/test/interfaces_tests.cpp
@@ -59,6 +59,21 @@ BOOST_AUTO_TEST_CASE(findFirstBlockWithTimeAndHeight)
     BOOST_CHECK(!chain->findFirstBlockWithTimeAndHeight(/* min_time= */ active.Tip()->GetBlockTimeMax() + 1, /* min_height= */ 0));
 }
 
+BOOST_AUTO_TEST_CASE(findNextBlock)
+{
+    auto chain = interfaces::MakeChain(m_node);
+    auto& active = ChainActive();
+    bool reorg;
+    uint256 hash;
+    BOOST_CHECK(chain->findNextBlock(active[20]->GetBlockHash(), 20, FoundBlock().hash(hash), &reorg));
+    BOOST_CHECK_EQUAL(hash, active[21]->GetBlockHash());
+    BOOST_CHECK_EQUAL(reorg, false);
+    BOOST_CHECK(!chain->findNextBlock(uint256(), 20, {}, &reorg));
+    BOOST_CHECK_EQUAL(reorg, true);
+    BOOST_CHECK(!chain->findNextBlock(active.Tip()->GetBlockHash(), active.Height(), {}, &reorg));
+    BOOST_CHECK_EQUAL(reorg, false);
+}
+
 BOOST_AUTO_TEST_CASE(findAncestorByHeight)
 {
     auto chain = interfaces::MakeChain(m_node);
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 6bda33c6c..3b7a5d273 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -3569,7 +3569,7 @@ UniValue rescanblockchain(const JSONRPCRequest& request)
     }
 
     CWallet::ScanResult result =
-        pwallet->ScanForWalletTransactions(start_block, stop_height, reserver, true /* fUpdate */);
+        pwallet->ScanForWalletTransactions(start_block, start_height, stop_height, reserver, true /* fUpdate */);
     switch (result.status) {
     case CWallet::ScanResult::SUCCESS:
         break;
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index fb5b0587d..160a672df 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -46,7 +46,7 @@ BOOST_FIXTURE_TEST_CASE(scan_for_wallet_transactions, TestChain100Setup)
     auto locked_chain = chain->lock();
     LockAssertion lock(::cs_main);
 
-    // Verify ScanForWalletTransactions accommodates a null start block.
+    // Verify ScanForWalletTransactions fails to read an unknown start block.
     {
         CWallet wallet(chain.get(), WalletLocation(), WalletDatabase::CreateDummy());
         {
@@ -56,8 +56,8 @@ BOOST_FIXTURE_TEST_CASE(scan_for_wallet_transactions, TestChain100Setup)
         AddKey(wallet, coinbaseKey);
         WalletRescanReserver reserver(&wallet);
         reserver.reserve();
-        CWallet::ScanResult result = wallet.ScanForWalletTransactions({} /* start_block */, {} /* stop_block */, reserver, false /* update */);
-        BOOST_CHECK_EQUAL(result.status, CWallet::ScanResult::SUCCESS);
+        CWallet::ScanResult result = wallet.ScanForWalletTransactions({} /* start_block */, 0 /* start_height */, {} /* max_height */, reserver, false /* update */);
+        BOOST_CHECK_EQUAL(result.status, CWallet::ScanResult::FAILURE);
         BOOST_CHECK(result.last_failed_block.IsNull());
         BOOST_CHECK(result.last_scanned_block.IsNull());
         BOOST_CHECK(!result.last_scanned_height);
@@ -75,7 +75,7 @@ BOOST_FIXTURE_TEST_CASE(scan_for_wallet_transactions, TestChain100Setup)
         AddKey(wallet, coinbaseKey);
         WalletRescanReserver reserver(&wallet);
         reserver.reserve();
-        CWallet::ScanResult result = wallet.ScanForWalletTransactions(oldTip->GetBlockHash(), {} /* stop_block */, reserver, false /* update */);
+        CWallet::ScanResult result = wallet.ScanForWalletTransactions(oldTip->GetBlockHash(), oldTip->nHeight, {} /* max_height */, reserver, false /* update */);
         BOOST_CHECK_EQUAL(result.status, CWallet::ScanResult::SUCCESS);
         BOOST_CHECK(result.last_failed_block.IsNull());
         BOOST_CHECK_EQUAL(result.last_scanned_block, newTip->GetBlockHash());
@@ -98,7 +98,7 @@ BOOST_FIXTURE_TEST_CASE(scan_for_wallet_transactions, TestChain100Setup)
         AddKey(wallet, coinbaseKey);
         WalletRescanReserver reserver(&wallet);
         reserver.reserve();
-        CWallet::ScanResult result = wallet.ScanForWalletTransactions(oldTip->GetBlockHash(), {} /* stop_block */, reserver, false /* update */);
+        CWallet::ScanResult result = wallet.ScanForWalletTransactions(oldTip->GetBlockHash(), oldTip->nHeight, {} /* max_height */, reserver, false /* update */);
         BOOST_CHECK_EQUAL(result.status, CWallet::ScanResult::FAILURE);
         BOOST_CHECK_EQUAL(result.last_failed_block, oldTip->GetBlockHash());
         BOOST_CHECK_EQUAL(result.last_scanned_block, newTip->GetBlockHash());
@@ -120,7 +120,7 @@ BOOST_FIXTURE_TEST_CASE(scan_for_wallet_transactions, TestChain100Setup)
         AddKey(wallet, coinbaseKey);
         WalletRescanReserver reserver(&wallet);
         reserver.reserve();
-        CWallet::ScanResult result = wallet.ScanForWalletTransactions(oldTip->GetBlockHash(), {} /* stop_block */, reserver, false /* update */);
+        CWallet::ScanResult result = wallet.ScanForWalletTransactions(oldTip->GetBlockHash(), oldTip->nHeight, {} /* max_height */, reserver, false /* update */);
         BOOST_CHECK_EQUAL(result.status, CWallet::ScanResult::FAILURE);
         BOOST_CHECK_EQUAL(result.last_failed_block, newTip->GetBlockHash());
         BOOST_CHECK(result.last_scanned_block.IsNull());
@@ -465,7 +465,7 @@ public:
         AddKey(*wallet, coinbaseKey);
         WalletRescanReserver reserver(wallet.get());
         reserver.reserve();
-        CWallet::ScanResult result = wallet->ScanForWalletTransactions(::ChainActive().Genesis()->GetBlockHash(), {} /* stop_block */, reserver, false /* update */);
+        CWallet::ScanResult result = wallet->ScanForWalletTransactions(::ChainActive().Genesis()->GetBlockHash(), 0 /* start_height */, {} /* max_height */, reserver, false /* update */);
         BOOST_CHECK_EQUAL(result.status, CWallet::ScanResult::SUCCESS);
         BOOST_CHECK_EQUAL(result.last_scanned_block, ::ChainActive().Tip()->GetBlockHash());
         BOOST_CHECK_EQUAL(*result.last_scanned_height, ::ChainActive().Height());
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 70d39a8fc..6d968e7ad 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1598,7 +1598,7 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
 
     if (start) {
         // TODO: this should take into account failure by ScanResult::USER_ABORT
-        ScanResult result = ScanForWalletTransactions(start_block, {} /* stop_block */, reserver, update);
+        ScanResult result = ScanForWalletTransactions(start_block, start_height, {} /* max_height */, reserver, update);
         if (result.status == ScanResult::FAILURE) {
             int64_t time_max;
             CHECK_NONFATAL(chain().findBlock(result.last_failed_block, FoundBlock().maxTime(time_max)));
@@ -1615,6 +1615,7 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
  *
  * @param[in] start_block Scan starting block. If block is not on the active
  *                        chain, the scan will return SUCCESS immediately.
+ * @param[in] start_height Height of start_block
  * @param[in] max_height  Optional max scanning height. If unset there is
  *                        no maximum and scanning can continue to the tip
  *
@@ -1628,7 +1629,7 @@ int64_t CWallet::RescanFromTime(int64_t startTime, const WalletRescanReserver& r
  * the main chain after to the addition of any new keys you want to detect
  * transactions for.
  */
-CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_block, Optional<int> max_height, const WalletRescanReserver& reserver, bool fUpdate)
+CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_block, int start_height, Optional<int> max_height, const WalletRescanReserver& reserver, bool fUpdate)
 {
     int64_t nNow = GetTime();
     int64_t start_time = GetTimeMillis();
@@ -1642,38 +1643,32 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
 
     fAbortRescan = false;
     ShowProgress(strprintf("%s " + _("Rescanning...").translated, GetDisplayName()), 0); // show rescan progress in GUI as dialog or on splashscreen, if -rescan on startup
-    uint256 tip_hash;
-    // The way the 'block_height' is initialized is just a workaround for the gcc bug #47679 since version 4.6.0.
-    Optional<int> block_height = MakeOptional(false, int());
-    double progress_begin;
-    double progress_end;
-    {
-        auto locked_chain = chain().lock();
-        if (Optional<int> tip_height = locked_chain->getHeight()) {
-            tip_hash = locked_chain->getBlockHash(*tip_height);
-        }
-        block_height = locked_chain->getBlockHeight(block_hash);
-        uint256 end_hash = tip_hash;
-        if (max_height) chain().findAncestorByHeight(tip_hash, *max_height, FoundBlock().hash(end_hash));
-        progress_begin = chain().guessVerificationProgress(block_hash);
-        progress_end = chain().guessVerificationProgress(end_hash);
-    }
+    uint256 tip_hash = WITH_LOCK(cs_wallet, return GetLastBlockHash());
+    uint256 end_hash = tip_hash;
+    if (max_height) chain().findAncestorByHeight(tip_hash, *max_height, FoundBlock().hash(end_hash));
+    double progress_begin = chain().guessVerificationProgress(block_hash);
+    double progress_end = chain().guessVerificationProgress(end_hash);
     double progress_current = progress_begin;
-    while (block_height && !fAbortRescan && !chain().shutdownRequested()) {
+    int block_height = start_height;
+    while (!fAbortRescan && !chain().shutdownRequested()) {
         m_scanning_progress = (progress_current - progress_begin) / (progress_end - progress_begin);
-        if (*block_height % 100 == 0 && progress_end - progress_begin > 0.0) {
+        if (block_height % 100 == 0 && progress_end - progress_begin > 0.0) {
             ShowProgress(strprintf("%s " + _("Rescanning...").translated, GetDisplayName()), std::max(1, std::min(99, (int)(m_scanning_progress * 100))));
         }
         if (GetTime() >= nNow + 60) {
             nNow = GetTime();
-            WalletLogPrintf("Still rescanning. At block %d. Progress=%f\n", *block_height, progress_current);
+            WalletLogPrintf("Still rescanning. At block %d. Progress=%f\n", block_height, progress_current);
         }
 
         CBlock block;
+        bool next_block;
+        uint256 next_block_hash;
+        bool reorg = false;
         if (chain().findBlock(block_hash, FoundBlock().data(block)) && !block.IsNull()) {
             auto locked_chain = chain().lock();
             LOCK(cs_wallet);
-            if (!locked_chain->getBlockHeight(block_hash)) {
+            next_block = chain().findNextBlock(block_hash, block_height, FoundBlock().hash(next_block_hash), &reorg);
+            if (reorg) {
                 // Abort scan if current block is no longer active, to prevent
                 // marking transactions as coming from the wrong block.
                 // TODO: This should return success instead of failure, see
@@ -1683,36 +1678,37 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
                 break;
             }
             for (size_t posInBlock = 0; posInBlock < block.vtx.size(); ++posInBlock) {
-                CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, *block_height, block_hash, posInBlock);
+                CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, block_height, block_hash, posInBlock);
                 SyncTransaction(block.vtx[posInBlock], confirm, fUpdate);
             }
             // scan succeeded, record block as most recent successfully scanned
             result.last_scanned_block = block_hash;
-            result.last_scanned_height = *block_height;
+            result.last_scanned_height = block_height;
         } else {
             // could not scan block, keep scanning but record this block as the most recent failure
             result.last_failed_block = block_hash;
             result.status = ScanResult::FAILURE;
+            next_block = chain().findNextBlock(block_hash, block_height, FoundBlock().hash(next_block_hash), &reorg);
         }
-        if (max_height && *block_height >= *max_height) {
+        if (max_height && block_height >= *max_height) {
             break;
         }
         {
             auto locked_chain = chain().lock();
-            Optional<int> tip_height = locked_chain->getHeight();
-            if (!tip_height || *tip_height <= block_height || !locked_chain->getBlockHeight(block_hash)) {
+            if (!next_block || reorg) {
                 // break successfully when rescan has reached the tip, or
                 // previous block is no longer on the chain due to a reorg
                 break;
             }
 
             // increment block and verification progress
-            block_hash = locked_chain->getBlockHash(++*block_height);
+            block_hash = next_block_hash;
+            ++block_height;
             progress_current = chain().guessVerificationProgress(block_hash);
 
             // handle updated tip hash
             const uint256 prev_tip_hash = tip_hash;
-            tip_hash = locked_chain->getBlockHash(*tip_height);
+            tip_hash = WITH_LOCK(cs_wallet, return GetLastBlockHash());
             if (!max_height && prev_tip_hash != tip_hash) {
                 // in case the tip has changed, update progress max
                 progress_end = chain().guessVerificationProgress(tip_hash);
@@ -1721,10 +1717,10 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
     }
     ShowProgress(strprintf("%s " + _("Rescanning...").translated, GetDisplayName()), 100); // hide progress dialog in GUI
     if (block_height && fAbortRescan) {
-        WalletLogPrintf("Rescan aborted at block %d. Progress=%f\n", *block_height, progress_current);
+        WalletLogPrintf("Rescan aborted at block %d. Progress=%f\n", block_height, progress_current);
         result.status = ScanResult::USER_ABORT;
     } else if (block_height && chain().shutdownRequested()) {
-        WalletLogPrintf("Rescan interrupted by shutdown request at block %d. Progress=%f\n", *block_height, progress_current);
+        WalletLogPrintf("Rescan interrupted by shutdown request at block %d. Progress=%f\n", block_height, progress_current);
         result.status = ScanResult::USER_ABORT;
     } else {
         WalletLogPrintf("Rescan completed in %15dms\n", GetTimeMillis() - start_time);
@@ -4049,7 +4045,7 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
 
         {
             WalletRescanReserver reserver(walletInstance.get());
-            if (!reserver.reserve() || (ScanResult::SUCCESS != walletInstance->ScanForWalletTransactions(locked_chain->getBlockHash(rescan_height), {} /* stop block */, reserver, true /* update */).status)) {
+            if (!reserver.reserve() || (ScanResult::SUCCESS != walletInstance->ScanForWalletTransactions(locked_chain->getBlockHash(rescan_height), rescan_height, {} /* max height */, reserver, true /* update */).status)) {
                 error = _("Failed to rescan the wallet during initialization").translated;
                 return nullptr;
             }
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index f105ccd17..28ec3d631 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -894,7 +894,7 @@ public:
         //! USER_ABORT.
         uint256 last_failed_block;
     };
-    ScanResult ScanForWalletTransactions(const uint256& first_block, Optional<int> max_height, const WalletRescanReserver& reserver, bool fUpdate);
+    ScanResult ScanForWalletTransactions(const uint256& start_block, int start_height, Optional<int> max_height, const WalletRescanReserver& reserver, bool fUpdate);
     void transactionRemovedFromMempool(const CTransactionRef &ptx) override;
     void ReacceptWalletTransactions() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     void ResendWalletTransactions();

From e958ff9ab5607da2cd321f29fc785a6d359e44f4 Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Wed, 22 Jan 2020 17:11:02 -0500
Subject: [PATCH 11/12] wallet: Avoid use of Chain::Lock in
 CWallet::CreateTransaction

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip, where it may set a different lock time.
---
 src/wallet/wallet.cpp | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 6d968e7ad..37c61991a 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2620,13 +2620,15 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, int& nC
     return true;
 }
 
-static bool IsCurrentForAntiFeeSniping(interfaces::Chain& chain, interfaces::Chain::Lock& locked_chain)
+static bool IsCurrentForAntiFeeSniping(interfaces::Chain& chain, const uint256& block_hash)
 {
     if (chain.isInitialBlockDownload()) {
         return false;
     }
     constexpr int64_t MAX_ANTI_FEE_SNIPING_TIP_AGE = 8 * 60 * 60; // in seconds
-    if (locked_chain.getBlockTime(*locked_chain.getHeight()) < (GetTime() - MAX_ANTI_FEE_SNIPING_TIP_AGE)) {
+    int64_t block_time;
+    CHECK_NONFATAL(chain.findBlock(block_hash, FoundBlock().time(block_time)));
+    if (block_time < (GetTime() - MAX_ANTI_FEE_SNIPING_TIP_AGE)) {
         return false;
     }
     return true;
@@ -2636,9 +2638,8 @@ static bool IsCurrentForAntiFeeSniping(interfaces::Chain& chain, interfaces::Cha
  * Return a height-based locktime for new transactions (uses the height of the
  * current chain tip unless we are not synced with the current chain
  */
-static uint32_t GetLocktimeForNewTransaction(interfaces::Chain& chain, interfaces::Chain::Lock& locked_chain)
+static uint32_t GetLocktimeForNewTransaction(interfaces::Chain& chain, const uint256& block_hash, int block_height)
 {
-    uint32_t const height = locked_chain.getHeight().get_value_or(-1);
     uint32_t locktime;
     // Discourage fee sniping.
     //
@@ -2660,8 +2661,8 @@ static uint32_t GetLocktimeForNewTransaction(interfaces::Chain& chain, interface
     // enough, that fee sniping isn't a problem yet, but by implementing a fix
     // now we ensure code won't be written that makes assumptions about
     // nLockTime that preclude a fix later.
-    if (IsCurrentForAntiFeeSniping(chain, locked_chain)) {
-        locktime = height;
+    if (IsCurrentForAntiFeeSniping(chain, block_hash)) {
+        locktime = block_height;
 
         // Secondly occasionally randomly pick a nLockTime even further back, so
         // that transactions that are delayed after signing for whatever reason,
@@ -2675,7 +2676,6 @@ static uint32_t GetLocktimeForNewTransaction(interfaces::Chain& chain, interface
         // unique "nLockTime fingerprint", set nLockTime to a constant.
         locktime = 0;
     }
-    assert(locktime <= height);
     assert(locktime < LOCKTIME_THRESHOLD);
     return locktime;
 }
@@ -2735,9 +2735,6 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
     }
 
     CMutableTransaction txNew;
-
-    txNew.nLockTime = GetLocktimeForNewTransaction(chain(), locked_chain);
-
     FeeCalculation feeCalc;
     CAmount nFeeNeeded;
     int nBytes;
@@ -2745,6 +2742,7 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
         std::set<CInputCoin> setCoins;
         auto locked_chain = chain().lock();
         LOCK(cs_wallet);
+        txNew.nLockTime = GetLocktimeForNewTransaction(chain(), GetLastBlockHash(), GetLastBlockHeight());
         {
             std::vector<COutput> vAvailableCoins;
             AvailableCoins(*locked_chain, vAvailableCoins, true, &coin_control, 1, MAX_MONEY, MAX_MONEY, 0);

From 48973402d8bccb673eaeb68b7aa86faa39d3cb8a Mon Sep 17 00:00:00 2001
From: Russell Yanofsky <russ@yanofsky.org>
Date: Wed, 22 Jan 2020 17:15:17 -0500
Subject: [PATCH 12/12] wallet: Avoid use of Chain::Lock in
 CWallet::GetKeyBirthTimes

This is a step toward removing the Chain::Lock class and reducing cs_main
locking.

This change only affects behavior in the case where wallet last block processed
falls behind the chain tip, where it will treat the last block processed as the
current tip.
---
 src/interfaces/chain.cpp |  7 -------
 src/interfaces/chain.h   |  3 ---
 src/wallet/wallet.cpp    | 25 +++++++++++++++----------
 3 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 2b2d3a4b8..c8311b298 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -80,13 +80,6 @@ class LockImpl : public Chain::Lock, public UniqueLock<RecursiveMutex>
         assert(block != nullptr);
         return block->GetBlockHash();
     }
-    int64_t getBlockTime(int height) override
-    {
-        LockAssertion lock(::cs_main);
-        CBlockIndex* block = ::ChainActive()[height];
-        assert(block != nullptr);
-        return block->GetBlockTime();
-    }
     bool haveBlockOnDisk(int height) override
     {
         LockAssertion lock(::cs_main);
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index ef5a002f5..a2d381b5c 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -100,9 +100,6 @@ public:
         //! Get block hash. Height must be valid or this function will abort.
         virtual uint256 getBlockHash(int height) = 0;
 
-        //! Get block time. Height must be valid or this function will abort.
-        virtual int64_t getBlockTime(int height) = 0;
-
         //! Check that the block is available on disk (i.e. has not been
         //! pruned), and contains transactions.
         virtual bool haveBlockOnDisk(int height) = 0;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 37c61991a..da8e7ee38 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -3554,12 +3554,13 @@ void CWallet::GetKeyBirthTimes(interfaces::Chain::Lock& locked_chain, std::map<C
     }
 
     // map in which we'll infer heights of other keys
-    const Optional<int> tip_height = locked_chain.getHeight();
-    const int max_height = tip_height && *tip_height > 144 ? *tip_height - 144 : 0; // the tip can be reorganized; use a 144-block safety margin
-    std::map<CKeyID, int> mapKeyFirstBlock;
+    std::map<CKeyID, const CWalletTx::Confirmation*> mapKeyFirstBlock;
+    CWalletTx::Confirmation max_confirm;
+    max_confirm.block_height = GetLastBlockHeight() > 144 ? GetLastBlockHeight() - 144 : 0; // the tip can be reorganized; use a 144-block safety margin
+    CHECK_NONFATAL(chain().findAncestorByHeight(GetLastBlockHash(), max_confirm.block_height, FoundBlock().hash(max_confirm.hashBlock)));
     for (const CKeyID &keyid : spk_man->GetKeys()) {
         if (mapKeyBirth.count(keyid) == 0)
-            mapKeyFirstBlock[keyid] = max_height;
+            mapKeyFirstBlock[keyid] = &max_confirm;
     }
 
     // if there are no such keys, we're done
@@ -3570,23 +3571,27 @@ void CWallet::GetKeyBirthTimes(interfaces::Chain::Lock& locked_chain, std::map<C
     for (const auto& entry : mapWallet) {
         // iterate over all wallet transactions...
         const CWalletTx &wtx = entry.second;
-        if (Optional<int> height = locked_chain.getBlockHeight(wtx.m_confirm.hashBlock)) {
+        if (wtx.m_confirm.status == CWalletTx::CONFIRMED) {
             // ... which are already in a block
             for (const CTxOut &txout : wtx.tx->vout) {
                 // iterate over all their outputs
                 for (const auto &keyid : GetAffectedKeys(txout.scriptPubKey, *spk_man)) {
                     // ... and all their affected keys
-                    std::map<CKeyID, int>::iterator rit = mapKeyFirstBlock.find(keyid);
-                    if (rit != mapKeyFirstBlock.end() && *height < rit->second)
-                        rit->second = *height;
+                    auto rit = mapKeyFirstBlock.find(keyid);
+                    if (rit != mapKeyFirstBlock.end() && wtx.m_confirm.block_height < rit->second->block_height) {
+                        rit->second = &wtx.m_confirm;
+                    }
                 }
             }
         }
     }
 
     // Extract block timestamps for those keys
-    for (const auto& entry : mapKeyFirstBlock)
-        mapKeyBirth[entry.first] = locked_chain.getBlockTime(entry.second) - TIMESTAMP_WINDOW; // block times can be 2h off
+    for (const auto& entry : mapKeyFirstBlock) {
+        int64_t block_time;
+        CHECK_NONFATAL(chain().findBlock(entry.second->hashBlock, FoundBlock().time(block_time)));
+        mapKeyBirth[entry.first] = block_time - TIMESTAMP_WINDOW; // block times can be 2h off
+    }
 }
 
 /**