Merge bitcoin/bitcoin#32950: validation: remove BLOCK_FAILED_CHILD

fb3e1bf9c9 test: check LoadBlockIndex correctly recomputes invalidity flags (stratospher)
29740c06ac validation: remove BLOCK_FAILED_MASK (stratospher)
b5b2956bda validation: reset BLOCK_FAILED_CHILD to BLOCK_FAILED_VALID when loading from disk (stratospher)
37bc207852 validation: stop using BLOCK_FAILED_CHILD (stratospher)
120c631e16 refactor: use clearer variables in InvalidateBlock() (stratospher)
18f11695c7 validation: don't update BLOCK_FAILED_VALID to BLOCK_FAILED_CHILD in InvalidateBlock (stratospher)

Pull request description:

  Fixes https://github.com/bitcoin/bitcoin/issues/32173

  even though we have a distinction between `BLOCK_FAILED_VALID` and `BLOCK_FAILED_CHILD` in the codebase,
  we don't use it for anything. Whenever we check for BlockStatus, we use `BLOCK_FAILED_MASK` which encompasses both of them.

  Since there is no functional difference between `BLOCK_FAILED_VALID` and `BLOCK_FAILED_CHILD` and it's added
  code complexity to correctly categorise them (ex: https://github.com/bitcoin/bitcoin/pull/31405#discussion_r1914366243, https://github.com/bitcoin/bitcoin/pull/16856#issuecomment-565506585), we could just remove it.

  Looking for conceptual feedback on whether it's better to improve handling of `BLOCK_FAILED_CHILD` in the codebase or remove `BLOCK_FAILED_CHILD`.

  Of less relevance, but it would also fix a `reconsiderblock` crash that could happen in the situation mentioned in https://github.com/bitcoin/bitcoin/issues/32173#issuecomment-2767030982

  Similar attempt in the past in https://github.com/bitcoin/bitcoin/pull/16856#issuecomment-568073859

ACKs for top commit:
  stickies-v:
    re-ACK fb3e1bf9c9
  alexanderwiederin:
    ACK fb3e1bf9c9
  mzumsande:
    re-ACK fb3e1bf9c9

Tree-SHA512: e97b739885c40a8c021966438e9767cc02bc183056236d6a8c64f6819347ae70c0fbcd71cc2528917560d9f4fd56aed45faf1b6c75d98de7b08b621693a97fbc

src/chain.h

@@ -77,8 +77,7 @@ enum BlockStatus : uint32_t {
     BLOCK_HAVE_MASK          =   BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO,
 
     BLOCK_FAILED_VALID       =   32, //!< stage after last reached validness failed
-    BLOCK_FAILED_CHILD       =   64, //!< descends from failed block
+    BLOCK_FAILED_CHILD       =   64, //!< Unused flag that was previously set when descending from failed block
-    BLOCK_FAILED_MASK        =   BLOCK_FAILED_VALID | BLOCK_FAILED_CHILD,
 
     BLOCK_OPT_WITNESS        =   128, //!< block data in blk*.dat was received with a witness-enforcing client
 
@@ -253,7 +252,7 @@ public:
     {
         AssertLockHeld(::cs_main);
         assert(!(nUpTo & ~BLOCK_VALID_MASK)); // Only validity flags allowed.
-        if (nStatus & BLOCK_FAILED_MASK)
+        if (nStatus & BLOCK_FAILED_VALID)
             return false;
         return ((nStatus & BLOCK_VALID_MASK) >= nUpTo);
     }
@@ -264,7 +263,7 @@ public:
     {
         AssertLockHeld(::cs_main);
         assert(!(nUpTo & ~BLOCK_VALID_MASK)); // Only validity flags allowed.
-        if (nStatus & BLOCK_FAILED_MASK) return false;
+        if (nStatus & BLOCK_FAILED_VALID) return false;
 
         if ((nStatus & BLOCK_VALID_MASK) < nUpTo) {
             nStatus = (nStatus & ~BLOCK_VALID_MASK) | nUpTo;

src/node/blockstorage.cpp

@@ -487,10 +487,18 @@ bool BlockManager::LoadBlockIndex(const std::optional<uint256>& snapshot_blockha
                 pindex->m_chain_tx_count = pindex->nTx;
             }
         }
-        if (!(pindex->nStatus & BLOCK_FAILED_MASK) && pindex->pprev && (pindex->pprev->nStatus & BLOCK_FAILED_MASK)) {
+
-            pindex->nStatus |= BLOCK_FAILED_CHILD;
+        if (pindex->nStatus & BLOCK_FAILED_CHILD) {
+            // BLOCK_FAILED_CHILD is deprecated, but may still exist on disk. Replace it with BLOCK_FAILED_VALID.
+            pindex->nStatus = (pindex->nStatus & ~BLOCK_FAILED_CHILD) | BLOCK_FAILED_VALID;
             m_dirty_blockindex.insert(pindex);
         }
+        if (!(pindex->nStatus & BLOCK_FAILED_VALID) && pindex->pprev && (pindex->pprev->nStatus & BLOCK_FAILED_VALID)) {
+            // All descendants of invalid blocks are invalid too.
+            pindex->nStatus |= BLOCK_FAILED_VALID;
+            m_dirty_blockindex.insert(pindex);
+        }
+
         if (pindex->pprev) {
             pindex->BuildSkip();
         }

src/rpc/blockchain.cpp

@@ -1595,7 +1595,7 @@ static RPCHelpMan getchaintips()
         if (active_chain.Contains(block)) {
             // This block is part of the currently active chain.
             status = "active";
-        } else if (block->nStatus & BLOCK_FAILED_MASK) {
+        } else if (block->nStatus & BLOCK_FAILED_VALID) {
             // This block or one of its ancestors is invalid.
             status = "invalid";
         } else if (!block->HaveNumChainTxs()) {

src/rpc/mining.cpp

@@ -742,7 +742,7 @@ static RPCHelpMan getblocktemplate()
             if (pindex) {
                 if (pindex->IsValid(BLOCK_VALID_SCRIPTS))
                     return "duplicate";
-                if (pindex->nStatus & BLOCK_FAILED_MASK)
+                if (pindex->nStatus & BLOCK_FAILED_VALID)
                     return "duplicate-invalid";
                 return "duplicate-inconclusive";
             }

src/test/blockchain_tests.cpp

@@ -130,28 +130,21 @@ BOOST_FIXTURE_TEST_CASE(invalidate_block, TestChain100Setup)
 
     // tip_to_invalidate just got invalidated, so it's BLOCK_FAILED_VALID
     WITH_LOCK(::cs_main, assert(tip_to_invalidate->nStatus & BLOCK_FAILED_VALID));
-    WITH_LOCK(::cs_main, assert((tip_to_invalidate->nStatus & BLOCK_FAILED_CHILD) == 0));
 
     // check all ancestors of the invalidated block are validated up to BLOCK_VALID_TRANSACTIONS and are not invalid
     auto pindex = tip_to_invalidate->pprev;
     while (pindex) {
         WITH_LOCK(::cs_main, assert(pindex->IsValid(BLOCK_VALID_TRANSACTIONS)));
-        WITH_LOCK(::cs_main, assert((pindex->nStatus & BLOCK_FAILED_MASK) == 0));
+        WITH_LOCK(::cs_main, assert((pindex->nStatus & BLOCK_FAILED_VALID) == 0));
         pindex = pindex->pprev;
     }
 
-    // check all descendants of the invalidated block are BLOCK_FAILED_CHILD
+    // check all descendants of the invalidated block are BLOCK_FAILED_VALID
     pindex = orig_tip;
     while (pindex && pindex != tip_to_invalidate) {
-        WITH_LOCK(::cs_main, assert((pindex->nStatus & BLOCK_FAILED_VALID) == 0));
+        WITH_LOCK(::cs_main, assert(pindex->nStatus & BLOCK_FAILED_VALID));
-        WITH_LOCK(::cs_main, assert(pindex->nStatus & BLOCK_FAILED_CHILD));
         pindex = pindex->pprev;
     }
-
-    // don't mark already invalidated block (orig_tip is BLOCK_FAILED_CHILD) with BLOCK_FAILED_VALID again
-    m_node.chainman->ActiveChainstate().InvalidateBlock(state, orig_tip);
-    WITH_LOCK(::cs_main, assert(orig_tip->nStatus & BLOCK_FAILED_CHILD));
-    WITH_LOCK(::cs_main, assert((orig_tip->nStatus & BLOCK_FAILED_VALID) == 0));
 }
 
 BOOST_AUTO_TEST_SUITE_END()

src/test/fuzz/block_index_tree.cpp

@@ -61,7 +61,7 @@ FUZZ_TARGET(block_index_tree, .init = initialize_block_index_tree)
                 // Receive a header building on an existing valid one. This assumes headers are valid, so PoW is not relevant here.
                 LOCK(cs_main);
                 CBlockIndex* prev_block = PickValue(fuzzed_data_provider, blocks);
-                if (!(prev_block->nStatus & BLOCK_FAILED_MASK)) {
+                if (!(prev_block->nStatus & BLOCK_FAILED_VALID)) {
                     CBlockHeader header = ConsumeBlockHeader(fuzzed_data_provider, prev_block->GetBlockHash(), nonce_counter);
                     CBlockIndex* index = blockman.AddToBlockIndex(header, chainman.m_best_header);
                     assert(index->nStatus & BLOCK_VALID_TREE);
@@ -74,7 +74,7 @@ FUZZ_TARGET(block_index_tree, .init = initialize_block_index_tree)
                 LOCK(cs_main);
                 CBlockIndex* index = PickValue(fuzzed_data_provider, blocks);
                 // Must be new to us and not known to be invalid (e.g. because of an invalid ancestor).
-                if (index->nTx == 0 && !(index->nStatus & BLOCK_FAILED_MASK)) {
+                if (index->nTx == 0 && !(index->nStatus & BLOCK_FAILED_VALID)) {
                     if (fuzzed_data_provider.ConsumeBool()) { // Invalid
                         BlockValidationState state;
                         state.Invalid(BlockValidationResult::BLOCK_CONSENSUS, "consensus-invalid");
@@ -124,7 +124,7 @@ FUZZ_TARGET(block_index_tree, .init = initialize_block_index_tree)
                     }
                     // Connect blocks, possibly fail
                     for (CBlockIndex* block : to_connect | std::views::reverse) {
-                        assert(!(block->nStatus & BLOCK_FAILED_MASK));
+                        assert(!(block->nStatus & BLOCK_FAILED_VALID));
                         assert(block->nStatus & BLOCK_HAVE_DATA);
                         if (!block->IsValid(BLOCK_VALID_SCRIPTS)) {
                             if (fuzzed_data_provider.ConsumeBool()) { // Invalid

src/test/fuzz/chain.cpp

@@ -50,8 +50,6 @@ FUZZ_TARGET(chain)
             BlockStatus::BLOCK_HAVE_UNDO,
             BlockStatus::BLOCK_HAVE_MASK,
             BlockStatus::BLOCK_FAILED_VALID,
-            BlockStatus::BLOCK_FAILED_CHILD,
-            BlockStatus::BLOCK_FAILED_MASK,
             BlockStatus::BLOCK_OPT_WITNESS,
         });
         if (block_status & ~BLOCK_VALID_MASK) {

src/test/validation_chainstatemanager_tests.cpp

@@ -591,6 +591,31 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_loadblockindex, TestChain100Setup)
     BOOST_CHECK_EQUAL(cs2.setBlockIndexCandidates.size(), num_indexes - last_assumed_valid_idx + 1);
 }
 
+BOOST_FIXTURE_TEST_CASE(loadblockindex_invalid_descendants, TestChain100Setup)
+{
+    LOCK(Assert(m_node.chainman)->GetMutex());
+    // consider the chain of blocks grand_parent <- parent <- child
+    // intentionally mark:
+    //   - grand_parent: BLOCK_FAILED_VALID
+    //   - parent: BLOCK_FAILED_CHILD
+    //   - child: not invalid
+    // Test that when the block index is loaded, all blocks are marked as BLOCK_FAILED_VALID
+    auto* child{m_node.chainman->ActiveChain().Tip()};
+    auto* parent{child->pprev};
+    auto* grand_parent{parent->pprev};
+    grand_parent->nStatus = (grand_parent->nStatus | BLOCK_FAILED_VALID);
+    parent->nStatus = (parent->nStatus & ~BLOCK_FAILED_VALID) | BLOCK_FAILED_CHILD;
+    child->nStatus = (child->nStatus & ~BLOCK_FAILED_VALID);
+
+    // Reload block index to recompute block status validity flags.
+    m_node.chainman->LoadBlockIndex();
+
+    // check grand_parent, parent, child is marked as BLOCK_FAILED_VALID after reloading the block index
+    BOOST_CHECK(grand_parent->nStatus & BLOCK_FAILED_VALID);
+    BOOST_CHECK(parent->nStatus & BLOCK_FAILED_VALID);
+    BOOST_CHECK(child->nStatus & BLOCK_FAILED_VALID);
+}
+
 //! Ensure that snapshot chainstate can be loaded when found on disk after a
 //! restart, and that new blocks can be connected to both chainstates.
 BOOST_FIXTURE_TEST_CASE(chainstatemanager_snapshot_init, SnapshotTestSetup)

src/validation.cpp

@@ -3173,7 +3173,7 @@ CBlockIndex* Chainstate::FindMostWorkChain()
             // which block files have been deleted.  Remove those as candidates
             // for the most work chain if we come across them; we can't switch
             // to a chain unless we have all the non-active-chain parent blocks.
-            bool fFailedChain = pindexTest->nStatus & BLOCK_FAILED_MASK;
+            bool fFailedChain = pindexTest->nStatus & BLOCK_FAILED_VALID;
             bool fMissingData = !(pindexTest->nStatus & BLOCK_HAVE_DATA);
             if (fFailedChain || fMissingData) {
                 // Candidate chain is not usable (either invalid or missing data)
@@ -3184,7 +3184,7 @@ CBlockIndex* Chainstate::FindMostWorkChain()
                 // Remove the entire chain from the set.
                 while (pindexTest != pindexFailed) {
                     if (fFailedChain) {
-                        pindexFailed->nStatus |= BLOCK_FAILED_CHILD;
+                        pindexFailed->nStatus |= BLOCK_FAILED_VALID;
                         m_blockman.m_dirty_blockindex.insert(pindexFailed);
                     } else if (fMissingData) {
                         // If we're missing data, then add back to m_blocks_unlinked,
@@ -3565,10 +3565,6 @@ bool Chainstate::InvalidateBlock(BlockValidationState& state, CBlockIndex* pinde
     assert(pindex);
     if (pindex->nHeight == 0) return false;
 
-    CBlockIndex* to_mark_failed = pindex;
-    bool pindex_was_in_chain = false;
-    int disconnected = 0;
-
     // We do not allow ActivateBestChain() to run while InvalidateBlock() is
     // running, as that could cause the tip to change while we disconnect
     // blocks.
@@ -3594,12 +3590,16 @@ bool Chainstate::InvalidateBlock(BlockValidationState& state, CBlockIndex* pinde
             // at least as good with CBlockIndexWorkComparator as the new tip.
             if (!m_chain.Contains(candidate) &&
                 !CBlockIndexWorkComparator()(candidate, pindex->pprev) &&
-                !(candidate->nStatus & BLOCK_FAILED_MASK)) {
+                !(candidate->nStatus & BLOCK_FAILED_VALID)) {
                 highpow_outofchain_headers.insert({candidate->nChainWork, candidate});
             }
         }
     }
 
+    CBlockIndex* to_mark_failed = pindex;
+    bool pindex_was_in_chain = false;
+    int disconnected = 0;
+
     // Disconnect (descendants of) pindex, and mark them invalid.
     while (true) {
         if (m_chainman.m_interrupt) break;
@@ -3613,7 +3613,7 @@ bool Chainstate::InvalidateBlock(BlockValidationState& state, CBlockIndex* pinde
         LOCK(MempoolMutex());
         if (!m_chain.Contains(pindex)) break;
         pindex_was_in_chain = true;
-        CBlockIndex *invalid_walk_tip = m_chain.Tip();
+        CBlockIndex* disconnected_tip{m_chain.Tip()};
 
         // ActivateBestChain considers blocks already in m_chain
         // unconditionally valid already, so force disconnect away from it.
@@ -3626,49 +3626,42 @@ bool Chainstate::InvalidateBlock(BlockValidationState& state, CBlockIndex* pinde
         // keeping the mempool up to date is probably futile anyway).
         MaybeUpdateMempoolForReorg(disconnectpool, /* fAddToMempool = */ (++disconnected <= 10) && ret);
         if (!ret) return false;
-        assert(invalid_walk_tip->pprev == m_chain.Tip());
+        CBlockIndex* new_tip{m_chain.Tip()};
+        assert(disconnected_tip->pprev == new_tip);
 
         // We immediately mark the disconnected blocks as invalid.
         // This prevents a case where pruned nodes may fail to invalidateblock
         // and be left unable to start as they have no tip candidates (as there
         // are no blocks that meet the "have data and are not invalid per
         // nStatus" criteria for inclusion in setBlockIndexCandidates).
-        invalid_walk_tip->nStatus |= BLOCK_FAILED_VALID;
+        disconnected_tip->nStatus |= BLOCK_FAILED_VALID;
-        m_blockman.m_dirty_blockindex.insert(invalid_walk_tip);
+        m_blockman.m_dirty_blockindex.insert(disconnected_tip);
-        setBlockIndexCandidates.erase(invalid_walk_tip);
+        setBlockIndexCandidates.erase(disconnected_tip);
-        setBlockIndexCandidates.insert(invalid_walk_tip->pprev);
+        setBlockIndexCandidates.insert(new_tip);
-        if (invalid_walk_tip == to_mark_failed->pprev && (to_mark_failed->nStatus & BLOCK_FAILED_VALID)) {
-            // We only want to mark the last disconnected block as BLOCK_FAILED_VALID; its children
-            // need to be BLOCK_FAILED_CHILD instead.
-            to_mark_failed->nStatus = (to_mark_failed->nStatus ^ BLOCK_FAILED_VALID) | BLOCK_FAILED_CHILD;
-            m_blockman.m_dirty_blockindex.insert(to_mark_failed);
-        }
 
         // Mark out-of-chain descendants of the invalidated block as invalid
-        // (possibly replacing a pre-existing BLOCK_FAILED_VALID with BLOCK_FAILED_CHILD)
         // Add any equal or more work headers that are not invalidated to setBlockIndexCandidates
         // Recalculate m_best_header if it became invalid.
-        auto candidate_it = highpow_outofchain_headers.lower_bound(invalid_walk_tip->pprev->nChainWork);
+        auto candidate_it = highpow_outofchain_headers.lower_bound(new_tip->nChainWork);
 
-        const bool best_header_needs_update{m_chainman.m_best_header->GetAncestor(invalid_walk_tip->nHeight) == invalid_walk_tip};
+        const bool best_header_needs_update{m_chainman.m_best_header->GetAncestor(disconnected_tip->nHeight) == disconnected_tip};
         if (best_header_needs_update) {
-            // pprev is definitely still valid at this point, but there may be better ones
+            // new_tip is definitely still valid at this point, but there may be better ones
-            m_chainman.m_best_header = invalid_walk_tip->pprev;
+            m_chainman.m_best_header = new_tip;
         }
 
         while (candidate_it != highpow_outofchain_headers.end()) {
             CBlockIndex* candidate{candidate_it->second};
-            if (candidate->GetAncestor(invalid_walk_tip->nHeight) == invalid_walk_tip) {
+            if (candidate->GetAncestor(disconnected_tip->nHeight) == disconnected_tip) {
-                // Children of failed blocks should be marked as BLOCK_FAILED_CHILD instead.
+                // Children of failed blocks are marked as BLOCK_FAILED_VALID.
-                candidate->nStatus &= ~BLOCK_FAILED_VALID;
+                candidate->nStatus |= BLOCK_FAILED_VALID;
-                candidate->nStatus |= BLOCK_FAILED_CHILD;
                 m_blockman.m_dirty_blockindex.insert(candidate);
                 // If invalidated, the block is irrelevant for setBlockIndexCandidates
                 // and for m_best_header and can be removed from the cache.
                 candidate_it = highpow_outofchain_headers.erase(candidate_it);
                 continue;
             }
-            if (!CBlockIndexWorkComparator()(candidate, invalid_walk_tip->pprev) &&
+            if (!CBlockIndexWorkComparator()(candidate, new_tip) &&
                 candidate->IsValid(BLOCK_VALID_TRANSACTIONS) &&
                 candidate->HaveNumChainTxs()) {
                 setBlockIndexCandidates.insert(candidate);
@@ -3682,9 +3675,8 @@ bool Chainstate::InvalidateBlock(BlockValidationState& state, CBlockIndex* pinde
             ++candidate_it;
         }
 
-        // Track the last disconnected block, so we can correct its BLOCK_FAILED_CHILD status in future
+        // Track the last disconnected block to call InvalidChainFound on it.
-        // iterations, or, if it's the last one, call InvalidChainFound on it.
+        to_mark_failed = disconnected_tip;
-        to_mark_failed = invalid_walk_tip;
     }
 
     m_chainman.CheckBlockIndex();
@@ -3697,7 +3689,7 @@ bool Chainstate::InvalidateBlock(BlockValidationState& state, CBlockIndex* pinde
         }
 
         // Mark pindex as invalid if it never was in the main chain
-        if (!pindex_was_in_chain && !(pindex->nStatus & BLOCK_FAILED_MASK)) {
+        if (!pindex_was_in_chain && !(pindex->nStatus & BLOCK_FAILED_VALID)) {
             pindex->nStatus |= BLOCK_FAILED_VALID;
             m_blockman.m_dirty_blockindex.insert(pindex);
             setBlockIndexCandidates.erase(pindex);
@@ -3748,7 +3740,7 @@ void Chainstate::SetBlockFailureFlags(CBlockIndex* invalid_block)
 
     for (auto& [_, block_index] : m_blockman.m_block_index) {
         if (invalid_block != &block_index && block_index.GetAncestor(invalid_block->nHeight) == invalid_block) {
-            block_index.nStatus = (block_index.nStatus & ~BLOCK_FAILED_VALID) | BLOCK_FAILED_CHILD;
+            block_index.nStatus |= BLOCK_FAILED_VALID;
             m_blockman.m_dirty_blockindex.insert(&block_index);
         }
     }
@@ -3761,8 +3753,8 @@ void Chainstate::ResetBlockFailureFlags(CBlockIndex *pindex) {
 
     // Remove the invalidity flag from this block and all its descendants and ancestors.
     for (auto& [_, block_index] : m_blockman.m_block_index) {
-        if ((block_index.nStatus & BLOCK_FAILED_MASK) && (block_index.GetAncestor(nHeight) == pindex || pindex->GetAncestor(block_index.nHeight) == &block_index)) {
+        if ((block_index.nStatus & BLOCK_FAILED_VALID) && (block_index.GetAncestor(nHeight) == pindex || pindex->GetAncestor(block_index.nHeight) == &block_index)) {
-            block_index.nStatus &= ~BLOCK_FAILED_MASK;
+            block_index.nStatus &= ~BLOCK_FAILED_VALID;
             m_blockman.m_dirty_blockindex.insert(&block_index);
             if (block_index.IsValid(BLOCK_VALID_TRANSACTIONS) && block_index.HaveNumChainTxs() && setBlockIndexCandidates.value_comp()(m_chain.Tip(), &block_index)) {
                 setBlockIndexCandidates.insert(&block_index);
@@ -4245,7 +4237,7 @@ bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValida
             CBlockIndex* pindex = &(miSelf->second);
             if (ppindex)
                 *ppindex = pindex;
-            if (pindex->nStatus & BLOCK_FAILED_MASK) {
+            if (pindex->nStatus & BLOCK_FAILED_VALID) {
                 LogDebug(BCLog::VALIDATION, "%s: block %s is marked invalid\n", __func__, hash.ToString());
                 return state.Invalid(BlockValidationResult::BLOCK_CACHED_INVALID, "duplicate-invalid",
                                      strprintf("block %s was previously marked invalid", hash.ToString()));
@@ -4266,7 +4258,7 @@ bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValida
             return state.Invalid(BlockValidationResult::BLOCK_MISSING_PREV, "prev-blk-not-found");
         }
         pindexPrev = &((*mi).second);
-        if (pindexPrev->nStatus & BLOCK_FAILED_MASK) {
+        if (pindexPrev->nStatus & BLOCK_FAILED_VALID) {
             LogDebug(BCLog::VALIDATION, "header %s has prev block invalid: %s\n", hash.ToString(), block.hashPrevBlock.ToString());
             return state.Invalid(BlockValidationResult::BLOCK_INVALID_PREV, "bad-prevblk");
         }
@@ -4960,7 +4952,7 @@ bool ChainstateManager::LoadBlockIndex()
                     chainstate->TryAddBlockIndexCandidate(pindex);
                 }
             }
-            if (pindex->nStatus & BLOCK_FAILED_MASK && (!m_best_invalid || pindex->nChainWork > m_best_invalid->nChainWork)) {
+            if (pindex->nStatus & BLOCK_FAILED_VALID && (!m_best_invalid || pindex->nChainWork > m_best_invalid->nChainWork)) {
                 m_best_invalid = pindex;
             }
             if (pindex->IsValid(BLOCK_VALID_TREE) && (m_best_header == nullptr || CBlockIndexWorkComparator()(m_best_header, pindex)))
@@ -5200,7 +5192,7 @@ void ChainstateManager::CheckBlockIndex() const
     // are not yet validated.
     CChain best_hdr_chain;
     assert(m_best_header);
-    assert(!(m_best_header->nStatus & BLOCK_FAILED_MASK));
+    assert(!(m_best_header->nStatus & BLOCK_FAILED_VALID));
     best_hdr_chain.SetTip(*m_best_header);
 
     std::multimap<const CBlockIndex*, const CBlockIndex*> forward;
@@ -5315,9 +5307,9 @@ void ChainstateManager::CheckBlockIndex() const
         if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_SCRIPTS) assert(pindexFirstNotScriptsValid == nullptr); // SCRIPTS valid implies all parents are SCRIPTS valid
         if (pindexFirstInvalid == nullptr) {
             // Checks for not-invalid blocks.
-            assert((pindex->nStatus & BLOCK_FAILED_MASK) == 0); // The failed mask cannot be set for blocks without invalid parents.
+            assert((pindex->nStatus & BLOCK_FAILED_VALID) == 0); // The failed flag cannot be set for blocks without invalid parents.
         } else {
-            assert(pindex->nStatus & BLOCK_FAILED_MASK); // Invalid blocks and their descendants must be marked as invalid
+            assert(pindex->nStatus & BLOCK_FAILED_VALID); // Invalid blocks and their descendants must be marked as invalid
         }
         // Make sure m_chain_tx_count sum is correctly computed.
         if (!pindex->pprev) {
@@ -5332,7 +5324,7 @@ void ChainstateManager::CheckBlockIndex() const
             assert((pindex->m_chain_tx_count != 0) == (pindex == snap_base));
         }
         // There should be no block with more work than m_best_header, unless it's known to be invalid
-        assert((pindex->nStatus & BLOCK_FAILED_MASK) || pindex->nChainWork <= m_best_header->nChainWork);
+        assert((pindex->nStatus & BLOCK_FAILED_VALID) || pindex->nChainWork <= m_best_header->nChainWork);
 
         // Chainstate-specific checks on setBlockIndexCandidates
         for (const auto& c : m_chainstates) {
@@ -5648,7 +5640,7 @@ util::Result<CBlockIndex*> ChainstateManager::ActivateSnapshot(
                           base_blockhash.ToString()))};
         }
 
-        bool start_block_invalid = snapshot_start_block->nStatus & BLOCK_FAILED_MASK;
+        bool start_block_invalid = snapshot_start_block->nStatus & BLOCK_FAILED_VALID;
         if (start_block_invalid) {
             return util::Error{Untranslated(strprintf("The base block header (%s) is part of an invalid chain", base_blockhash.ToString()))};
         }
@@ -6293,7 +6285,7 @@ void ChainstateManager::RecalculateBestHeader()
     AssertLockHeld(cs_main);
     m_best_header = ActiveChain().Tip();
     for (auto& entry : m_blockman.m_block_index) {
-        if (!(entry.second.nStatus & BLOCK_FAILED_MASK) && m_best_header->nChainWork < entry.second.nChainWork) {
+        if (!(entry.second.nStatus & BLOCK_FAILED_VALID) && m_best_header->nChainWork < entry.second.nChainWork) {
             m_best_header = &entry.second;
         }
     }