Merge #19927: validation: Reduce direct g_chainman usage

72a1d5c6f3834e206719ee5121df7727aed5b786 validation: Remove review-only comments + assertions (Carl Dong)
3756853b15902d63f4b5a3129e8b5d82e84e125b docs: Move FindFilesToPrune{,Manual} doxygen comment (Carl Dong)
485899a93c6f5fff62090907efb0ac938992e1fb style: Make FindFilesToPrune{,Manual} match style guide (Carl Dong)
3f5b5f3f6db0e5716911b3fba1460ce327e8a845 validation: Move FindFilesToPrune{,Manual} to BlockManager (Carl Dong)
f8d4975ab3fcd3553843cf0862251289c88c106b validation: Move PruneOneBlockFile to BlockManager (Carl Dong)
74f73c783d46b012f375d819e2cd09c792820cd5 validation: Pass in chainman to UnloadBlockIndex (Carl Dong)
4668ded6d6ea4299d998abbb57543f37519812e2 validation: Move ~CMainCleanup logic to ~BlockManager (Carl Dong)

Pull request description:

  This PR paves the way for de-globalizing `g_chainman` entirely by removing the usage of `g_chainman` in the following functions/methods:
  - `~CMainCleanup`
  - `CChainState::FlushStateToDisk`
  - `UnloadBlockIndex`

  The remaining direct uses of `g_chainman` are as follows:
  1. In initialization codepaths:
  	- `AppTests`
  	- `AppInitMain`
  	- `TestingSetup::TestingSetup`
  2. `::ChainstateActive`
  3. `LookupBlockIndex`
  	- Note: `LookupBlockIndex` is used extensively throughout the codebase and require a much larger set of changes, therefore I've left it out of this initial PR

ACKs for top commit:
  MarcoFalke:
    re-ACK 72a1d5c6f3 👚
  jnewbery:
    utACK 72a1d5c6f3834e206719ee5121df7727aed5b786

Tree-SHA512: 944a4fa8405eecf39706ff944375d6824373aaeea849d11473f08181eff26b12f70043a8348a5b08e6e9021b243b481842fbdfbc7c3140ca795fce3688b7f5c3

6 files changed, 72 insertions, 69 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 132acbfc81..5ad807cbac 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1563,7 +1563,7 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
                 chainman.m_total_coinstip_cache = nCoinCacheUsage;
                 chainman.m_total_coinsdb_cache = nCoinDBCache;
 
-                UnloadBlockIndex(node.mempool.get());
+                UnloadBlockIndex(node.mempool.get(), chainman);
 
                 // new CBlockTreeDB tries to delete the existing file, which
                 // fails if it's still open from the previous loop. Close it first:
diff --git a/src/qt/test/apptests.cpp b/src/qt/test/apptests.cpp
index 0b5c341548..8dffd2f59f 100644
--- a/src/qt/test/apptests.cpp
+++ b/src/qt/test/apptests.cpp
@@ -84,8 +84,11 @@ void AppTests::appTests()
     // Reset global state to avoid interfering with later tests.
     LogInstance().DisconnectTestLogger();
     AbortShutdown();
-    UnloadBlockIndex(/* mempool */ nullptr);
-    WITH_LOCK(::cs_main, g_chainman.Reset());
+    {
+        LOCK(cs_main);
+        UnloadBlockIndex(/* mempool */ nullptr, g_chainman);
+        g_chainman.Reset();
+    }
 }
 
 //! Entry point for BitcoinGUI tests.
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 08aff07448..2d3137e1e2 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -187,7 +187,7 @@ TestingSetup::~TestingSetup()
     m_node.connman.reset();
     m_node.banman.reset();
     m_node.args = nullptr;
-    UnloadBlockIndex(m_node.mempool.get());
+    UnloadBlockIndex(m_node.mempool.get(), *m_node.chainman);
     m_node.mempool.reset();
     m_node.scheduler.reset();
     m_node.chainman->Reset();
diff --git a/src/validation.cpp b/src/validation.cpp
index 7020b59cb8..d4463bf17b 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -198,9 +198,6 @@ CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& loc
 
 std::unique_ptr<CBlockTreeDB> pblocktree;
 
-// See definition for documentation
-static void FindFilesToPruneManual(ChainstateManager& chainman, std::set<int>& setFilesToPrune, int nManualPruneHeight);
-static void FindFilesToPrune(ChainstateManager& chainman, std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight);
 bool CheckInputScripts(const CTransaction& tx, TxValidationState &state, const CCoinsViewCache &inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
 static FILE* OpenUndoFile(const FlatFilePos &pos, bool fReadOnly = false);
 static FlatFileSeq BlockFileSeq();
@@ -2299,11 +2296,11 @@ bool CChainState::FlushStateToDisk(
             if (nManualPruneHeight > 0) {
                 LOG_TIME_MILLIS_WITH_CATEGORY("find files to prune (manual)", BCLog::BENCH);
 
-                FindFilesToPruneManual(g_chainman, setFilesToPrune, nManualPruneHeight);
+                m_blockman.FindFilesToPruneManual(setFilesToPrune, nManualPruneHeight, m_chain.Height());
             } else {
                 LOG_TIME_MILLIS_WITH_CATEGORY("find files to prune", BCLog::BENCH);
 
-                FindFilesToPrune(g_chainman, setFilesToPrune, chainparams.PruneAfterHeight());
+                m_blockman.FindFilesToPrune(setFilesToPrune, chainparams.PruneAfterHeight(), m_chain.Height(), IsInitialBlockDownload());
                 fCheckForPruning = false;
             }
             if (!setFilesToPrune.empty()) {
@@ -3909,12 +3906,12 @@ uint64_t CalculateCurrentUsage()
     return retval;
 }
 
-void ChainstateManager::PruneOneBlockFile(const int fileNumber)
+void BlockManager::PruneOneBlockFile(const int fileNumber)
 {
     AssertLockHeld(cs_main);
     LOCK(cs_LastBlockFile);
 
-    for (const auto& entry : m_blockman.m_block_index) {
+    for (const auto& entry : m_block_index) {
         CBlockIndex* pindex = entry.second;
         if (pindex->nFile == fileNumber) {
             pindex->nStatus &= ~BLOCK_HAVE_DATA;
@@ -3928,12 +3925,12 @@ void ChainstateManager::PruneOneBlockFile(const int fileNumber)
             // to be downloaded again in order to consider its chain, at which
             // point it would be considered as a candidate for
             // m_blocks_unlinked or setBlockIndexCandidates.
-            auto range = m_blockman.m_blocks_unlinked.equal_range(pindex->pprev);
+            auto range = 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) {
-                    m_blockman.m_blocks_unlinked.erase(_it);
+                    m_blocks_unlinked.erase(_it);
                 }
             }
         }
@@ -3954,22 +3951,23 @@ void UnlinkPrunedFiles(const std::set<int>& setFilesToPrune)
     }
 }
 
-/* Calculate the block/rev files to delete based on height specified by user with RPC command pruneblockchain */
-static void FindFilesToPruneManual(ChainstateManager& chainman, std::set<int>& setFilesToPrune, int nManualPruneHeight)
+void BlockManager::FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight, int chain_tip_height)
 {
     assert(fPruneMode && nManualPruneHeight > 0);
 
     LOCK2(cs_main, cs_LastBlockFile);
-    if (::ChainActive().Tip() == nullptr)
+    if (chain_tip_height < 0) {
         return;
+    }
 
     // last block to prune is the lesser of (user-specified height, MIN_BLOCKS_TO_KEEP from the tip)
-    unsigned int nLastBlockWeCanPrune = std::min((unsigned)nManualPruneHeight, ::ChainActive().Tip()->nHeight - MIN_BLOCKS_TO_KEEP);
-    int count=0;
+    unsigned int nLastBlockWeCanPrune = std::min((unsigned)nManualPruneHeight, chain_tip_height - MIN_BLOCKS_TO_KEEP);
+    int count = 0;
     for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
-        if (vinfoBlockFile[fileNumber].nSize == 0 || vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune)
+        if (vinfoBlockFile[fileNumber].nSize == 0 || vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune) {
             continue;
-        chainman.PruneOneBlockFile(fileNumber);
+        }
+        PruneOneBlockFile(fileNumber);
         setFilesToPrune.insert(fileNumber);
         count++;
     }
@@ -3987,46 +3985,31 @@ void PruneBlockFilesManual(int nManualPruneHeight)
     }
 }
 
-/**
- * Prune block and undo files (blk???.dat and undo???.dat) so that the disk space used is less than a user-defined target.
- * The user sets the target (in MB) on the command line or in config file.  This will be run on startup and whenever new
- * space is allocated in a block or undo file, staying below the target. Changing back to unpruned requires a reindex
- * (which in this case means the blockchain must be re-downloaded.)
- *
- * Pruning functions are called from FlushStateToDisk when the global fCheckForPruning flag has been set.
- * Block and undo files are deleted in lock-step (when blk00003.dat is deleted, so is rev00003.dat.)
- * Pruning cannot take place until the longest chain is at least a certain length (100000 on mainnet, 1000 on testnet, 1000 on regtest).
- * Pruning will never delete a block within a defined distance (currently 288) from the active chain's tip.
- * The block index is updated by unsetting HAVE_DATA and HAVE_UNDO for any blocks that were stored in the deleted files.
- * A db flag records the fact that at least some block files have been pruned.
- *
- * @param[out]   setFilesToPrune   The set of file indices that can be unlinked will be returned
- */
-static void FindFilesToPrune(ChainstateManager& chainman, std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight)
+void BlockManager::FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight, int chain_tip_height, bool is_ibd)
 {
     LOCK2(cs_main, cs_LastBlockFile);
-    if (::ChainActive().Tip() == nullptr || nPruneTarget == 0) {
+    if (chain_tip_height < 0 || nPruneTarget == 0) {
         return;
     }
-    if ((uint64_t)::ChainActive().Tip()->nHeight <= nPruneAfterHeight) {
+    if ((uint64_t)chain_tip_height <= nPruneAfterHeight) {
         return;
     }
 
-    unsigned int nLastBlockWeCanPrune = ::ChainActive().Tip()->nHeight - MIN_BLOCKS_TO_KEEP;
+    unsigned int nLastBlockWeCanPrune = chain_tip_height - MIN_BLOCKS_TO_KEEP;
     uint64_t nCurrentUsage = CalculateCurrentUsage();
     // We don't check to prune until after we've allocated new space for files
     // So we should leave a buffer under our target to account for another allocation
     // before the next pruning.
     uint64_t nBuffer = BLOCKFILE_CHUNK_SIZE + UNDOFILE_CHUNK_SIZE;
     uint64_t nBytesToPrune;
-    int count=0;
+    int count = 0;
 
     if (nCurrentUsage + nBuffer >= nPruneTarget) {
         // On a prune event, the chainstate DB is flushed.
         // To avoid excessive prune events negating the benefit of high dbcache
         // values, we should not prune too rapidly.
         // So when pruning in IBD, increase the buffer a bit to avoid a re-prune too soon.
-        if (::ChainstateActive().IsInitialBlockDownload()) {
+        if (is_ibd) {
             // Since this is only relevant during IBD, we use a fixed 10%
             nBuffer += nPruneTarget / 10;
         }
@@ -4034,17 +4017,20 @@ static void FindFilesToPrune(ChainstateManager& chainman, std::set<int>& setFile
         for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
             nBytesToPrune = vinfoBlockFile[fileNumber].nSize + vinfoBlockFile[fileNumber].nUndoSize;
 
-            if (vinfoBlockFile[fileNumber].nSize == 0)
+            if (vinfoBlockFile[fileNumber].nSize == 0) {
                 continue;
+            }
 
-            if (nCurrentUsage + nBuffer < nPruneTarget)  // are we below our target?
+            if (nCurrentUsage + nBuffer < nPruneTarget) { // are we below our target?
                 break;
+            }
 
             // don't prune files that could have a block within MIN_BLOCKS_TO_KEEP of the main chain's tip but keep scanning
-            if (vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune)
+            if (vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune) {
                 continue;
+            }
 
-            chainman.PruneOneBlockFile(fileNumber);
+            PruneOneBlockFile(fileNumber);
             // Queue up the files for removal
             setFilesToPrune.insert(fileNumber);
             nCurrentUsage -= nBytesToPrune;
@@ -4602,10 +4588,10 @@ void CChainState::UnloadBlockIndex() {
 // May NOT be used after any connections are up as much
 // of the peer-processing logic assumes a consistent
 // block index state
-void UnloadBlockIndex(CTxMemPool* mempool)
+void UnloadBlockIndex(CTxMemPool* mempool, ChainstateManager& chainman)
 {
     LOCK(cs_main);
-    g_chainman.Unload();
+    chainman.Unload();
     pindexBestInvalid = nullptr;
     pindexBestHeader = nullptr;
     if (mempool) mempool->clear();
@@ -5220,20 +5206,6 @@ double GuessVerificationProgress(const ChainTxData& data, const CBlockIndex *pin
     return std::min<double>(pindex->nChainTx / fTxTotal, 1.0);
 }
 
-class CMainCleanup
-{
-public:
-    CMainCleanup() {}
-    ~CMainCleanup() {
-        // block headers
-        BlockMap::iterator it1 = g_chainman.BlockIndex().begin();
-        for (; it1 != g_chainman.BlockIndex().end(); it1++)
-            delete (*it1).second;
-        g_chainman.BlockIndex().clear();
-    }
-};
-static CMainCleanup instance_of_cmaincleanup;
-
 Optional<uint256> ChainstateManager::SnapshotBlockhash() const {
     if (m_active_chainstate != nullptr) {
         // If a snapshot chainstate exists, it will always be our active.
diff --git a/src/validation.h b/src/validation.h
index 0da62093a3..d88bd07765 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -157,7 +157,7 @@ void LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, FlatFi
 /** Ensures we have a genesis block in the block tree, possibly writing one to disk. */
 bool LoadGenesisBlock(const CChainParams& chainparams);
 /** Unload database information */
-void UnloadBlockIndex(CTxMemPool* mempool);
+void UnloadBlockIndex(CTxMemPool* mempool, ChainstateManager& chainman);
 /** Run an instance of the script checking thread */
 void ThreadScriptCheck(int worker_num);
 /**
@@ -352,7 +352,31 @@ struct CBlockIndexWorkComparator
  * This data is used mostly in `CChainState` - information about, e.g.,
  * candidate tips is not maintained here.
  */
-class BlockManager {
+class BlockManager
+{
+    friend CChainState;
+
+private:
+    /* Calculate the block/rev files to delete based on height specified by user with RPC command pruneblockchain */
+    void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight, int chain_tip_height);
+
+    /**
+     * Prune block and undo files (blk???.dat and undo???.dat) so that the disk space used is less than a user-defined target.
+     * The user sets the target (in MB) on the command line or in config file.  This will be run on startup and whenever new
+     * space is allocated in a block or undo file, staying below the target. Changing back to unpruned requires a reindex
+     * (which in this case means the blockchain must be re-downloaded.)
+     *
+     * Pruning functions are called from FlushStateToDisk when the global fCheckForPruning flag has been set.
+     * Block and undo files are deleted in lock-step (when blk00003.dat is deleted, so is rev00003.dat.)
+     * Pruning cannot take place until the longest chain is at least a certain length (100000 on mainnet, 1000 on testnet, 1000 on regtest).
+     * Pruning will never delete a block within a defined distance (currently 288) from the active chain's tip.
+     * The block index is updated by unsetting HAVE_DATA and HAVE_UNDO for any blocks that were stored in the deleted files.
+     * A db flag records the fact that at least some block files have been pruned.
+     *
+     * @param[out]   setFilesToPrune   The set of file indices that can be unlinked will be returned
+     */
+    void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight, int chain_tip_height, bool is_ibd);
+
 public:
     BlockMap m_block_index GUARDED_BY(cs_main);
 
@@ -403,6 +427,9 @@ public:
     /** Create a new block index entry for a given block hash */
     CBlockIndex* InsertBlockIndex(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
+    //! Mark one block file as pruned (modify associated database entries)
+    void PruneOneBlockFile(const int fileNumber) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
     /**
      * If a block header hasn't already been seen, call CheckBlockHeader on it, ensure
      * that it doesn't descend from an invalid block, and then add it to m_block_index.
@@ -412,6 +439,10 @@ public:
         BlockValidationState& state,
         const CChainParams& chainparams,
         CBlockIndex** ppindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    ~BlockManager() {
+        Unload();
+    }
 };
 
 /**
@@ -895,9 +926,6 @@ public:
      */
     bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& block, BlockValidationState& state, const CChainParams& chainparams, const CBlockIndex** ppindex = nullptr) LOCKS_EXCLUDED(cs_main);
 
-    //! Mark one block file as pruned (modify associated database entries)
-    void PruneOneBlockFile(const int fileNumber) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
-
     //! Load the block tree and coins database from disk, initializing state if we're running with -reindex
     bool LoadBlockIndex(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index 6b98482f98..4393bb7701 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -126,7 +126,7 @@ BOOST_FIXTURE_TEST_CASE(scan_for_wallet_transactions, TestChain100Setup)
     // Prune the older block file.
     {
         LOCK(cs_main);
-        Assert(m_node.chainman)->PruneOneBlockFile(oldTip->GetBlockPos().nFile);
+        Assert(m_node.chainman)->m_blockman.PruneOneBlockFile(oldTip->GetBlockPos().nFile);
     }
     UnlinkPrunedFiles({oldTip->GetBlockPos().nFile});
 
@@ -152,7 +152,7 @@ BOOST_FIXTURE_TEST_CASE(scan_for_wallet_transactions, TestChain100Setup)
     // Prune the remaining block file.
     {
         LOCK(cs_main);
-        Assert(m_node.chainman)->PruneOneBlockFile(newTip->GetBlockPos().nFile);
+        Assert(m_node.chainman)->m_blockman.PruneOneBlockFile(newTip->GetBlockPos().nFile);
     }
     UnlinkPrunedFiles({newTip->GetBlockPos().nFile});
 
@@ -189,7 +189,7 @@ BOOST_FIXTURE_TEST_CASE(importmulti_rescan, TestChain100Setup)
     // Prune the older block file.
     {
         LOCK(cs_main);
-        Assert(m_node.chainman)->PruneOneBlockFile(oldTip->GetBlockPos().nFile);
+        Assert(m_node.chainman)->m_blockman.PruneOneBlockFile(oldTip->GetBlockPos().nFile);
     }
     UnlinkPrunedFiles({oldTip->GetBlockPos().nFile});