Merge #16194: refactor: share blockmetadata with BlockManager

682a1d0f2004d808b87b3106d0dfae547005e638 refactoring: remove mapBlockIndex global (James O'Beirne)
55d525ab9004631d30dcc60a1ec5d9cd6c6afe56 refactoring: make pindexBestInvalid internal to validation.cpp (James O'Beirne)
4ed55dfcd7894fd5ba6395f244a17ab1f8e786d4 refactoring: add block_index_candidates arg to LoadBlockIndex (James O'Beirne)
613c46fe9e39f55b0f0daa18fee20b4120db2539 refactoring: move block metadata structures into BlockManager (James O'Beirne)

Pull request description:

  This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11):

  Parent PR: #15606
  Issue: #15605
  Specification: https://github.com/jamesob/assumeutxo-docs/tree/2019-04-proposal/proposal

  ---

  Under an assumeutxo model, we have multiple CChainState instances in use at once in order to support background validation. Currently, each CChainState instance has its own mapBlockIndex, a collection of linked block headers, in addition to a few other data structures that are related to maintenance of the block tree but not necessarily to any given chainstate.

  In order to avoid duplicating this data across chainstates, this change moves chainstate-agnostic block metadata (and related behavior) into a class, `BlockManager`. Chainstates are parameterized with a reference to a blockmanager instance and in practice they share the same instance.

  Most of this change is conceptually move-only, though the diff is somewhat muddled. The first commit can be reviewed slightly more easily with `--color-moved=dimmed_zebra`. Admittedly, that commit is pretty unwieldy; I tried to split it up after the fact with `git add --patch`, but that was difficult because of git's inability to split hunks past a certain point. Some of the moves also ended up being obscured when done over separate commits.

ACKs for top commit:
  MarcoFalke:
    ACK 682a1d0f2004d808b87b3106d0dfae547005e638
  ryanofsky:
    utACK 682a1d0f2004d808b87b3106d0dfae547005e638, only changes since last review were rebase and fixing conflict on a moved line
  ariard:
    utACK 682a1d0. Most of the changes are move-only, with main problem being to avoid creating circular dependencies between `BlockManager` and `CChainState`. Tested, comments are mostly nits, feel free to ignore them

Tree-SHA512: 738d8d06539ba53acf4bd2d48ae000473e645bbc4e63d798d55d247a4d5a4f781b73538ed590f6407be9ab402ea9d395570ea20bff0a4b9ce747bcc1600c5108

1 files changed, 116 insertions, 91 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 262b6856a4..0bc6167bad 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -77,7 +77,11 @@ bool CBlockIndexWorkComparator::operator()(const CBlockIndex *pa, const CBlockIn
     return false;
 }
 
-static CChainState g_chainstate;
+namespace {
+BlockManager g_blockman;
+} // anon namespace
+
+static CChainState g_chainstate(g_blockman);
 
 CChainState& ChainstateActive() { return g_chainstate; }
 
@@ -95,7 +99,6 @@ CChain& ChainActive() { return g_chainstate.m_chain; }
  */
 RecursiveMutex cs_main;
 
-BlockMap& mapBlockIndex = ::ChainstateActive().mapBlockIndex;
 CBlockIndex *pindexBestHeader = nullptr;
 Mutex g_best_block_mutex;
 std::condition_variable g_best_block_cv;
@@ -125,12 +128,7 @@ CScript COINBASE_FLAGS;
 
 // Internal stuff
 namespace {
-    CBlockIndex *&pindexBestInvalid = ::ChainstateActive().pindexBestInvalid;
-
-    /** All pairs A->B, where A (or one of its ancestors) misses transactions, but B has transactions.
-     * Pruned nodes may have entries where B is missing data.
-     */
-    std::multimap<CBlockIndex*, CBlockIndex*>& mapBlocksUnlinked = ::ChainstateActive().mapBlocksUnlinked;
+    CBlockIndex* pindexBestInvalid = nullptr;
 
     CCriticalSection cs_LastBlockFile;
     std::vector<CBlockFileInfo> vinfoBlockFile;
@@ -148,6 +146,13 @@ namespace {
     std::set<int> setDirtyFileInfo;
 } // anon namespace
 
+CBlockIndex* LookupBlockIndex(const uint256& hash)
+{
+    AssertLockHeld(cs_main);
+    BlockMap::const_iterator it = g_blockman.m_block_index.find(hash);
+    return it == g_blockman.m_block_index.end() ? nullptr : it->second;
+}
+
 CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator)
 {
     AssertLockHeld(cs_main);
@@ -1047,6 +1052,11 @@ bool CChainState::IsInitialBlockDownload() const
 
 static CBlockIndex *pindexBestForkTip = nullptr, *pindexBestForkBase = nullptr;
 
+BlockMap& BlockIndex()
+{
+    return g_blockman.m_block_index;
+}
+
 static void AlertNotify(const std::string& strMessage)
 {
     uiInterface.NotifyAlertChanged();
@@ -1160,7 +1170,7 @@ void static InvalidChainFound(CBlockIndex* pindexNew) EXCLUSIVE_LOCKS_REQUIRED(c
 void CChainState::InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state) {
     if (state.GetReason() != ValidationInvalidReason::BLOCK_MUTATED) {
         pindex->nStatus |= BLOCK_FAILED_VALID;
-        m_failed_blocks.insert(pindex);
+        m_blockman.m_failed_blocks.insert(pindex);
         setDirtyBlockIndex.insert(pindex);
         setBlockIndexCandidates.erase(pindex);
         InvalidChainFound(pindex);
@@ -1695,8 +1705,8 @@ bool CChainState::ConnectBlock(const CBlock& block, CValidationState& state, CBl
         //  relative to a piece of software is an objective fact these defaults can be easily reviewed.
         // This setting doesn't force the selection of any particular chain but makes validating some faster by
         //  effectively caching the result of part of the verification.
-        BlockMap::const_iterator  it = mapBlockIndex.find(hashAssumeValid);
-        if (it != mapBlockIndex.end()) {
+        BlockMap::const_iterator  it = m_blockman.m_block_index.find(hashAssumeValid);
+        if (it != m_blockman.m_block_index.end()) {
             if (it->second->GetAncestor(pindex->nHeight) == pindex &&
                 pindexBestHeader->GetAncestor(pindex->nHeight) == pindex &&
                 pindexBestHeader->nChainWork >= nMinimumChainWork) {
@@ -2366,10 +2376,11 @@ CBlockIndex* CChainState::FindMostWorkChain() {
                     if (fFailedChain) {
                         pindexFailed->nStatus |= BLOCK_FAILED_CHILD;
                     } else if (fMissingData) {
-                        // If we're missing data, then add back to mapBlocksUnlinked,
+                        // If we're missing data, then add back to m_blocks_unlinked,
                         // so that if the block arrives in the future we can try adding
                         // to setBlockIndexCandidates again.
-                        mapBlocksUnlinked.insert(std::make_pair(pindexFailed->pprev, pindexFailed));
+                        m_blockman.m_blocks_unlinked.insert(
+                            std::make_pair(pindexFailed->pprev, pindexFailed));
                     }
                     setBlockIndexCandidates.erase(pindexFailed);
                     pindexFailed = pindexFailed->pprev;
@@ -2720,12 +2731,12 @@ bool CChainState::InvalidateBlock(CValidationState& state, const CChainParams& c
         to_mark_failed->nStatus |= BLOCK_FAILED_VALID;
         setDirtyBlockIndex.insert(to_mark_failed);
         setBlockIndexCandidates.erase(to_mark_failed);
-        m_failed_blocks.insert(to_mark_failed);
+        m_blockman.m_failed_blocks.insert(to_mark_failed);
 
         // The resulting new best tip may not be in setBlockIndexCandidates anymore, so
         // add it again.
-        BlockMap::iterator it = mapBlockIndex.begin();
-        while (it != mapBlockIndex.end()) {
+        BlockMap::iterator it = m_blockman.m_block_index.begin();
+        while (it != m_blockman.m_block_index.end()) {
             if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->HaveTxsDownloaded() && !setBlockIndexCandidates.value_comp()(it->second, m_chain.Tip())) {
                 setBlockIndexCandidates.insert(it->second);
             }
@@ -2752,8 +2763,8 @@ void CChainState::ResetBlockFailureFlags(CBlockIndex *pindex) {
     int nHeight = pindex->nHeight;
 
     // Remove the invalidity flag from this block and all its descendants.
-    BlockMap::iterator it = mapBlockIndex.begin();
-    while (it != mapBlockIndex.end()) {
+    BlockMap::iterator it = m_blockman.m_block_index.begin();
+    while (it != m_blockman.m_block_index.end()) {
         if (!it->second->IsValid() && it->second->GetAncestor(nHeight) == pindex) {
             it->second->nStatus &= ~BLOCK_FAILED_MASK;
             setDirtyBlockIndex.insert(it->second);
@@ -2764,7 +2775,7 @@ void CChainState::ResetBlockFailureFlags(CBlockIndex *pindex) {
                 // Reset invalid block marker if it was pointing to one of those.
                 pindexBestInvalid = nullptr;
             }
-            m_failed_blocks.erase(it->second);
+            m_blockman.m_failed_blocks.erase(it->second);
         }
         it++;
     }
@@ -2774,7 +2785,7 @@ void CChainState::ResetBlockFailureFlags(CBlockIndex *pindex) {
         if (pindex->nStatus & BLOCK_FAILED_MASK) {
             pindex->nStatus &= ~BLOCK_FAILED_MASK;
             setDirtyBlockIndex.insert(pindex);
-            m_failed_blocks.erase(pindex);
+            m_blockman.m_failed_blocks.erase(pindex);
         }
         pindex = pindex->pprev;
     }
@@ -2784,14 +2795,14 @@ void ResetBlockFailureFlags(CBlockIndex *pindex) {
     return ::ChainstateActive().ResetBlockFailureFlags(pindex);
 }
 
-CBlockIndex* CChainState::AddToBlockIndex(const CBlockHeader& block)
+CBlockIndex* BlockManager::AddToBlockIndex(const CBlockHeader& block)
 {
     AssertLockHeld(cs_main);
 
     // Check for duplicate
     uint256 hash = block.GetHash();
-    BlockMap::iterator it = mapBlockIndex.find(hash);
-    if (it != mapBlockIndex.end())
+    BlockMap::iterator it = m_block_index.find(hash);
+    if (it != m_block_index.end())
         return it->second;
 
     // Construct new block index object
@@ -2800,10 +2811,10 @@ CBlockIndex* CChainState::AddToBlockIndex(const CBlockHeader& block)
     // to avoid miners withholding blocks but broadcasting headers, to get a
     // competitive advantage.
     pindexNew->nSequenceId = 0;
-    BlockMap::iterator mi = mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
+    BlockMap::iterator mi = m_block_index.insert(std::make_pair(hash, pindexNew)).first;
     pindexNew->phashBlock = &((*mi).first);
-    BlockMap::iterator miPrev = mapBlockIndex.find(block.hashPrevBlock);
-    if (miPrev != mapBlockIndex.end())
+    BlockMap::iterator miPrev = m_block_index.find(block.hashPrevBlock);
+    if (miPrev != m_block_index.end())
     {
         pindexNew->pprev = (*miPrev).second;
         pindexNew->nHeight = pindexNew->pprev->nHeight + 1;
@@ -2852,17 +2863,17 @@ void CChainState::ReceivedBlockTransactions(const CBlock& block, CBlockIndex* pi
             if (m_chain.Tip() == nullptr || !setBlockIndexCandidates.value_comp()(pindex, m_chain.Tip())) {
                 setBlockIndexCandidates.insert(pindex);
             }
-            std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> range = mapBlocksUnlinked.equal_range(pindex);
+            std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> range = m_blockman.m_blocks_unlinked.equal_range(pindex);
             while (range.first != range.second) {
                 std::multimap<CBlockIndex*, CBlockIndex*>::iterator it = range.first;
                 queue.push_back(it->second);
                 range.first++;
-                mapBlocksUnlinked.erase(it);
+                m_blockman.m_blocks_unlinked.erase(it);
             }
         }
     } else {
         if (pindexNew->pprev && pindexNew->pprev->IsValid(BLOCK_VALID_TREE)) {
-            mapBlocksUnlinked.insert(std::make_pair(pindexNew->pprev, pindexNew));
+            m_blockman.m_blocks_unlinked.insert(std::make_pair(pindexNew->pprev, pindexNew));
         }
     }
 }
@@ -3117,7 +3128,7 @@ static bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationSta
     if (fCheckpointsEnabled) {
         // Don't accept any forks from the main chain prior to last checkpoint.
         // GetLastCheckpoint finds the last checkpoint in MapCheckpoints that's in our
-        // MapBlockIndex.
+        // g_blockman.m_block_index.
         CBlockIndex* pcheckpoint = GetLastCheckpoint(params.Checkpoints());
         if (pcheckpoint && nHeight < pcheckpoint->nHeight)
             return state.Invalid(ValidationInvalidReason::BLOCK_CHECKPOINT, error("%s: forked chain older than last checkpoint (height %d)", __func__, nHeight), REJECT_CHECKPOINT, "bad-fork-prior-to-checkpoint");
@@ -3230,15 +3241,15 @@ static bool ContextualCheckBlock(const CBlock& block, CValidationState& state, c
     return true;
 }
 
-bool CChainState::AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex)
+bool BlockManager::AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex)
 {
     AssertLockHeld(cs_main);
     // Check for duplicate
     uint256 hash = block.GetHash();
-    BlockMap::iterator miSelf = mapBlockIndex.find(hash);
+    BlockMap::iterator miSelf = m_block_index.find(hash);
     CBlockIndex *pindex = nullptr;
     if (hash != chainparams.GetConsensus().hashGenesisBlock) {
-        if (miSelf != mapBlockIndex.end()) {
+        if (miSelf != m_block_index.end()) {
             // Block header is already known.
             pindex = miSelf->second;
             if (ppindex)
@@ -3253,8 +3264,8 @@ bool CChainState::AcceptBlockHeader(const CBlockHeader& block, CValidationState&
 
         // Get prev block index
         CBlockIndex* pindexPrev = nullptr;
-        BlockMap::iterator mi = mapBlockIndex.find(block.hashPrevBlock);
-        if (mi == mapBlockIndex.end())
+        BlockMap::iterator mi = m_block_index.find(block.hashPrevBlock);
+        if (mi == m_block_index.end())
             return state.Invalid(ValidationInvalidReason::BLOCK_MISSING_PREV, error("%s: prev block not found", __func__), 0, "prev-blk-not-found");
         pindexPrev = (*mi).second;
         if (pindexPrev->nStatus & BLOCK_FAILED_MASK)
@@ -3306,8 +3317,6 @@ bool CChainState::AcceptBlockHeader(const CBlockHeader& block, CValidationState&
     if (ppindex)
         *ppindex = pindex;
 
-    CheckBlockIndex(chainparams.GetConsensus());
-
     return true;
 }
 
@@ -3319,7 +3328,10 @@ bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& headers, CValidatio
         LOCK(cs_main);
         for (const CBlockHeader& header : headers) {
             CBlockIndex *pindex = nullptr; // Use a temp pindex instead of ppindex to avoid a const_cast
-            if (!::ChainstateActive().AcceptBlockHeader(header, state, chainparams, &pindex)) {
+            bool accepted = g_blockman.AcceptBlockHeader(header, state, chainparams, &pindex);
+            ::ChainstateActive().CheckBlockIndex(chainparams.GetConsensus());
+
+            if (!accepted) {
                 if (first_invalid) *first_invalid = header;
                 return false;
             }
@@ -3362,7 +3374,10 @@ bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CVali
     CBlockIndex *pindexDummy = nullptr;
     CBlockIndex *&pindex = ppindex ? *ppindex : pindexDummy;
 
-    if (!AcceptBlockHeader(block, state, chainparams, &pindex))
+    bool accepted_header = m_blockman.AcceptBlockHeader(block, state, chainparams, &pindex);
+    CheckBlockIndex(chainparams.GetConsensus());
+
+    if (!accepted_header)
         return false;
 
     // Try to process all requested blocks that we don't have, but only
@@ -3513,7 +3528,7 @@ void PruneOneBlockFile(const int fileNumber)
 {
     LOCK(cs_LastBlockFile);
 
-    for (const auto& entry : mapBlockIndex) {
+    for (const auto& entry : g_blockman.m_block_index) {
         CBlockIndex* pindex = entry.second;
         if (pindex->nFile == fileNumber) {
             pindex->nStatus &= ~BLOCK_HAVE_DATA;
@@ -3523,16 +3538,16 @@ void PruneOneBlockFile(const int fileNumber)
             pindex->nUndoPos = 0;
             setDirtyBlockIndex.insert(pindex);
 
-            // Prune from mapBlocksUnlinked -- any block we prune would have
+            // Prune from m_blocks_unlinked -- any block we prune would have
             // to be downloaded again in order to consider its chain, at which
             // point it would be considered as a candidate for
-            // mapBlocksUnlinked or setBlockIndexCandidates.
-            std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> range = mapBlocksUnlinked.equal_range(pindex->pprev);
+            // m_blocks_unlinked or setBlockIndexCandidates.
+            auto range = g_blockman.m_blocks_unlinked.equal_range(pindex->pprev);
             while (range.first != range.second) {
                 std::multimap<CBlockIndex *, CBlockIndex *>::iterator _it = range.first;
                 range.first++;
                 if (_it->second == pindex) {
-                    mapBlocksUnlinked.erase(_it);
+                    g_blockman.m_blocks_unlinked.erase(_it);
                 }
             }
         }
@@ -3681,7 +3696,7 @@ fs::path GetBlockPosFilename(const FlatFilePos &pos)
     return BlockFileSeq().FileName(pos);
 }
 
-CBlockIndex * CChainState::InsertBlockIndex(const uint256& hash)
+CBlockIndex * BlockManager::InsertBlockIndex(const uint256& hash)
 {
     AssertLockHeld(cs_main);
 
@@ -3689,27 +3704,30 @@ CBlockIndex * CChainState::InsertBlockIndex(const uint256& hash)
         return nullptr;
 
     // Return existing
-    BlockMap::iterator mi = mapBlockIndex.find(hash);
-    if (mi != mapBlockIndex.end())
+    BlockMap::iterator mi = m_block_index.find(hash);
+    if (mi != m_block_index.end())
         return (*mi).second;
 
     // Create new
     CBlockIndex* pindexNew = new CBlockIndex();
-    mi = mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
+    mi = m_block_index.insert(std::make_pair(hash, pindexNew)).first;
     pindexNew->phashBlock = &((*mi).first);
 
     return pindexNew;
 }
 
-bool CChainState::LoadBlockIndex(const Consensus::Params& consensus_params, CBlockTreeDB& blocktree)
+bool BlockManager::LoadBlockIndex(
+    const Consensus::Params& consensus_params,
+    CBlockTreeDB& blocktree,
+    std::set<CBlockIndex*, CBlockIndexWorkComparator>& block_index_candidates)
 {
     if (!blocktree.LoadBlockIndexGuts(consensus_params, [this](const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main) { return this->InsertBlockIndex(hash); }))
         return false;
 
     // Calculate nChainWork
     std::vector<std::pair<int, CBlockIndex*> > vSortedByHeight;
-    vSortedByHeight.reserve(mapBlockIndex.size());
-    for (const std::pair<const uint256, CBlockIndex*>& item : mapBlockIndex)
+    vSortedByHeight.reserve(m_block_index.size());
+    for (const std::pair<const uint256, CBlockIndex*>& item : m_block_index)
     {
         CBlockIndex* pindex = item.second;
         vSortedByHeight.push_back(std::make_pair(pindex->nHeight, pindex));
@@ -3729,7 +3747,7 @@ bool CChainState::LoadBlockIndex(const Consensus::Params& consensus_params, CBlo
                     pindex->nChainTx = pindex->pprev->nChainTx + pindex->nTx;
                 } else {
                     pindex->nChainTx = 0;
-                    mapBlocksUnlinked.insert(std::make_pair(pindex->pprev, pindex));
+                    m_blocks_unlinked.insert(std::make_pair(pindex->pprev, pindex));
                 }
             } else {
                 pindex->nChainTx = pindex->nTx;
@@ -3739,8 +3757,9 @@ bool CChainState::LoadBlockIndex(const Consensus::Params& consensus_params, CBlo
             pindex->nStatus |= BLOCK_FAILED_CHILD;
             setDirtyBlockIndex.insert(pindex);
         }
-        if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && (pindex->HaveTxsDownloaded() || pindex->pprev == nullptr))
-            setBlockIndexCandidates.insert(pindex);
+        if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && (pindex->HaveTxsDownloaded() || pindex->pprev == nullptr)) {
+            block_index_candidates.insert(pindex);
+        }
         if (pindex->nStatus & BLOCK_FAILED_MASK && (!pindexBestInvalid || pindex->nChainWork > pindexBestInvalid->nChainWork))
             pindexBestInvalid = pindex;
         if (pindex->pprev)
@@ -3752,9 +3771,21 @@ bool CChainState::LoadBlockIndex(const Consensus::Params& consensus_params, CBlo
     return true;
 }
 
+void BlockManager::Unload() {
+    m_failed_blocks.clear();
+    m_blocks_unlinked.clear();
+
+    for (const BlockMap::value_type& entry : m_block_index) {
+        delete entry.second;
+    }
+
+    m_block_index.clear();
+}
+
 bool static LoadBlockIndexDB(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
 {
-    if (!::ChainstateActive().LoadBlockIndex(chainparams.GetConsensus(), *pblocktree))
+    if (!g_blockman.LoadBlockIndex(
+            chainparams.GetConsensus(), *pblocktree, ::ChainstateActive().setBlockIndexCandidates))
         return false;
 
     // Load block file info
@@ -3777,7 +3808,7 @@ bool static LoadBlockIndexDB(const CChainParams& chainparams) EXCLUSIVE_LOCKS_RE
     // Check presence of blk files
     LogPrintf("Checking all blk files are present...\n");
     std::set<int> setBlkDataFiles;
-    for (const std::pair<const uint256, CBlockIndex*>& item : mapBlockIndex)
+    for (const std::pair<const uint256, CBlockIndex*>& item : g_blockman.m_block_index)
     {
         CBlockIndex* pindex = item.second;
         if (pindex->nStatus & BLOCK_HAVE_DATA) {
@@ -3976,16 +4007,16 @@ bool CChainState::ReplayBlocks(const CChainParams& params, CCoinsView* view)
     const CBlockIndex* pindexNew;            // New tip during the interrupted flush.
     const CBlockIndex* pindexFork = nullptr; // Latest block common to both the old and the new tip.
 
-    if (mapBlockIndex.count(hashHeads[0]) == 0) {
+    if (m_blockman.m_block_index.count(hashHeads[0]) == 0) {
         return error("ReplayBlocks(): reorganization to unknown block requested");
     }
-    pindexNew = mapBlockIndex[hashHeads[0]];
+    pindexNew = m_blockman.m_block_index[hashHeads[0]];
 
     if (!hashHeads[1].IsNull()) { // The old tip is allowed to be 0, indicating it's the first flush.
-        if (mapBlockIndex.count(hashHeads[1]) == 0) {
+        if (m_blockman.m_block_index.count(hashHeads[1]) == 0) {
             return error("ReplayBlocks(): reorganization from unknown block requested");
         }
-        pindexOld = mapBlockIndex[hashHeads[1]];
+        pindexOld = m_blockman.m_block_index[hashHeads[1]];
         pindexFork = LastCommonAncestor(pindexOld, pindexNew);
         assert(pindexFork != nullptr);
     }
@@ -4051,10 +4082,10 @@ void CChainState::EraseBlockData(CBlockIndex* index)
     setDirtyBlockIndex.insert(index);
     // Update indexes
     setBlockIndexCandidates.erase(index);
-    std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> ret = mapBlocksUnlinked.equal_range(index->pprev);
+    auto ret = m_blockman.m_blocks_unlinked.equal_range(index->pprev);
     while (ret.first != ret.second) {
         if (ret.first->second == index) {
-            mapBlocksUnlinked.erase(ret.first++);
+            m_blockman.m_blocks_unlinked.erase(ret.first++);
         } else {
             ++ret.first;
         }
@@ -4074,7 +4105,7 @@ bool CChainState::RewindBlockIndex(const CChainParams& params)
     // blocks will be dealt with below (releasing cs_main in between).
     {
         LOCK(cs_main);
-        for (const auto& entry : mapBlockIndex) {
+        for (const auto& entry : m_blockman.m_block_index) {
             if (IsWitnessEnabled(entry.second->pprev, params.GetConsensus()) && !(entry.second->nStatus & BLOCK_OPT_WITNESS) && !m_chain.Contains(entry.second)) {
                 EraseBlockData(entry.second);
             }
@@ -4180,7 +4211,6 @@ bool RewindBlockIndex(const CChainParams& params) {
 
 void CChainState::UnloadBlockIndex() {
     nBlockSequenceId = 1;
-    m_failed_blocks.clear();
     setBlockIndexCandidates.clear();
 }
 
@@ -4191,10 +4221,10 @@ void UnloadBlockIndex()
 {
     LOCK(cs_main);
     ::ChainActive().SetTip(nullptr);
+    g_blockman.Unload();
     pindexBestInvalid = nullptr;
     pindexBestHeader = nullptr;
     mempool.clear();
-    mapBlocksUnlinked.clear();
     vinfoBlockFile.clear();
     nLastBlockFile = 0;
     setDirtyBlockIndex.clear();
@@ -4203,11 +4233,6 @@ void UnloadBlockIndex()
     for (int b = 0; b < VERSIONBITS_NUM_BITS; b++) {
         warningcache[b].clear();
     }
-
-    for (const BlockMap::value_type& entry : mapBlockIndex) {
-        delete entry.second;
-    }
-    mapBlockIndex.clear();
     fHavePruned = false;
 
     ::ChainstateActive().UnloadBlockIndex();
@@ -4220,7 +4245,7 @@ bool LoadBlockIndex(const CChainParams& chainparams)
     if (!fReindex) {
         bool ret = LoadBlockIndexDB(chainparams);
         if (!ret) return false;
-        needs_init = mapBlockIndex.empty();
+        needs_init = g_blockman.m_block_index.empty();
     }
 
     if (needs_init) {
@@ -4240,10 +4265,10 @@ bool CChainState::LoadGenesisBlock(const CChainParams& chainparams)
     LOCK(cs_main);
 
     // Check whether we're already initialized by checking for genesis in
-    // mapBlockIndex. Note that we can't use m_chain here, since it is
+    // m_blockman.m_block_index. Note that we can't use m_chain here, since it is
     // set based on the coins db, not the block index db, which is the only
     // thing loaded at this point.
-    if (mapBlockIndex.count(chainparams.GenesisBlock().GetHash()))
+    if (m_blockman.m_block_index.count(chainparams.GenesisBlock().GetHash()))
         return true;
 
     try {
@@ -4251,7 +4276,7 @@ bool CChainState::LoadGenesisBlock(const CChainParams& chainparams)
         FlatFilePos blockPos = SaveBlockToDisk(block, 0, chainparams, nullptr);
         if (blockPos.IsNull())
             return error("%s: writing genesis block to disk failed", __func__);
-        CBlockIndex *pindex = AddToBlockIndex(block);
+        CBlockIndex *pindex = m_blockman.AddToBlockIndex(block);
         ReceivedBlockTransactions(block, pindex, blockPos, chainparams.GetConsensus());
     } catch (const std::runtime_error& e) {
         return error("%s: failed to write genesis block: %s", __func__, e.what());
@@ -4396,20 +4421,20 @@ void CChainState::CheckBlockIndex(const Consensus::Params& consensusParams)
     LOCK(cs_main);
 
     // During a reindex, we read the genesis block and call CheckBlockIndex before ActivateBestChain,
-    // so we have the genesis block in mapBlockIndex but no active chain.  (A few of the tests when
-    // iterating the block tree require that m_chain has been initialized.)
+    // so we have the genesis block in m_blockman.m_block_index but no active chain. (A few of the
+    // tests when iterating the block tree require that m_chain has been initialized.)
     if (m_chain.Height() < 0) {
-        assert(mapBlockIndex.size() <= 1);
+        assert(m_blockman.m_block_index.size() <= 1);
         return;
     }
 
     // Build forward-pointing map of the entire block tree.
     std::multimap<CBlockIndex*,CBlockIndex*> forward;
-    for (const std::pair<const uint256, CBlockIndex*>& entry : mapBlockIndex) {
+    for (const std::pair<const uint256, CBlockIndex*>& entry : m_blockman.m_block_index) {
         forward.insert(std::make_pair(entry.second->pprev, entry.second));
     }
 
-    assert(forward.size() == mapBlockIndex.size());
+    assert(forward.size() == m_blockman.m_block_index.size());
 
     std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangeGenesis = forward.equal_range(nullptr);
     CBlockIndex *pindex = rangeGenesis.first->second;
@@ -4463,7 +4488,7 @@ void CChainState::CheckBlockIndex(const Consensus::Params& consensusParams)
         assert(pindex->nHeight == nHeight); // nHeight must be consistent.
         assert(pindex->pprev == nullptr || pindex->nChainWork >= pindex->pprev->nChainWork); // For every block except the genesis block, the chainwork must be larger than the parent's.
         assert(nHeight < 2 || (pindex->pskip && (pindex->pskip->nHeight < nHeight))); // The pskip pointer must point back for all but the first 2 blocks.
-        assert(pindexFirstNotTreeValid == nullptr); // All mapBlockIndex entries must at least be TREE valid
+        assert(pindexFirstNotTreeValid == nullptr); // All m_blockman.m_block_index entries must at least be TREE valid
         if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_TREE) assert(pindexFirstNotTreeValid == nullptr); // TREE valid implies all parents are TREE valid
         if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_CHAIN) assert(pindexFirstNotChainValid == nullptr); // CHAIN valid implies all parents are CHAIN valid
         if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_SCRIPTS) assert(pindexFirstNotScriptsValid == nullptr); // SCRIPTS valid implies all parents are SCRIPTS valid
@@ -4482,13 +4507,13 @@ void CChainState::CheckBlockIndex(const Consensus::Params& consensusParams)
                 }
                 // If some parent is missing, then it could be that this block was in
                 // setBlockIndexCandidates but had to be removed because of the missing data.
-                // In this case it must be in mapBlocksUnlinked -- see test below.
+                // In this case it must be in m_blocks_unlinked -- see test below.
             }
         } else { // If this block sorts worse than the current tip or some ancestor's block has never been seen, it cannot be in setBlockIndexCandidates.
             assert(setBlockIndexCandidates.count(pindex) == 0);
         }
-        // Check whether this block is in mapBlocksUnlinked.
-        std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangeUnlinked = mapBlocksUnlinked.equal_range(pindex->pprev);
+        // Check whether this block is in m_blocks_unlinked.
+        std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangeUnlinked = m_blockman.m_blocks_unlinked.equal_range(pindex->pprev);
         bool foundInUnlinked = false;
         while (rangeUnlinked.first != rangeUnlinked.second) {
             assert(rangeUnlinked.first->first == pindex->pprev);
@@ -4499,22 +4524,22 @@ void CChainState::CheckBlockIndex(const Consensus::Params& consensusParams)
             rangeUnlinked.first++;
         }
         if (pindex->pprev && (pindex->nStatus & BLOCK_HAVE_DATA) && pindexFirstNeverProcessed != nullptr && pindexFirstInvalid == nullptr) {
-            // If this block has block data available, some parent was never received, and has no invalid parents, it must be in mapBlocksUnlinked.
+            // If this block has block data available, some parent was never received, and has no invalid parents, it must be in m_blocks_unlinked.
             assert(foundInUnlinked);
         }
-        if (!(pindex->nStatus & BLOCK_HAVE_DATA)) assert(!foundInUnlinked); // Can't be in mapBlocksUnlinked if we don't HAVE_DATA
-        if (pindexFirstMissing == nullptr) assert(!foundInUnlinked); // We aren't missing data for any parent -- cannot be in mapBlocksUnlinked.
+        if (!(pindex->nStatus & BLOCK_HAVE_DATA)) assert(!foundInUnlinked); // Can't be in m_blocks_unlinked if we don't HAVE_DATA
+        if (pindexFirstMissing == nullptr) assert(!foundInUnlinked); // We aren't missing data for any parent -- cannot be in m_blocks_unlinked.
         if (pindex->pprev && (pindex->nStatus & BLOCK_HAVE_DATA) && pindexFirstNeverProcessed == nullptr && pindexFirstMissing != nullptr) {
             // We HAVE_DATA for this block, have received data for all parents at some point, but we're currently missing data for some parent.
             assert(fHavePruned); // We must have pruned.
-            // This block may have entered mapBlocksUnlinked if:
+            // This block may have entered m_blocks_unlinked if:
             //  - it has a descendant that at some point had more work than the
             //    tip, and
             //  - we tried switching to that descendant but were missing
             //    data for some intermediate block between m_chain and the
             //    tip.
             // So if this block is itself better than m_chain.Tip() and it wasn't in
-            // setBlockIndexCandidates, then it must be in mapBlocksUnlinked.
+            // setBlockIndexCandidates, then it must be in m_blocks_unlinked.
             if (!CBlockIndexWorkComparator()(pindex, m_chain.Tip()) && setBlockIndexCandidates.count(pindex) == 0) {
                 if (pindexFirstInvalid == nullptr) {
                     assert(foundInUnlinked);
@@ -4758,10 +4783,10 @@ public:
     CMainCleanup() {}
     ~CMainCleanup() {
         // block headers
-        BlockMap::iterator it1 = mapBlockIndex.begin();
-        for (; it1 != mapBlockIndex.end(); it1++)
+        BlockMap::iterator it1 = g_blockman.m_block_index.begin();
+        for (; it1 != g_blockman.m_block_index.end(); it1++)
             delete (*it1).second;
-        mapBlockIndex.clear();
+        g_blockman.m_block_index.clear();
     }
 };
 static CMainCleanup instance_of_cmaincleanup;