There are some potential feefilter cleanups mentioned and motivated in comment https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-805808485 . If you address the locking one, please be careful and make sure that `round()` is only called under a lock. See https://github.com/bitcoin/bitcoin/pull/21509#issuecomment-807992199

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ProcessBlock(pfrom, pblock, true);
            LOCK(cs_main); 
            if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS)) {
                
                
                
                
                MarkBlockAsReceived(pblock->GetHash());
            }
        }
        return;
    }
    if (msg_type == NetMsgType::BLOCKTXN)
    {
        
        if (fImporting || fReindex) {
            LogPrint(BCLog::NET, "Unexpected blocktxn message received from peer %d\n", pfrom.GetId());
            return;
        }
        BlockTransactions resp;
        vRecv >> resp;
        std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
        bool fBlockRead = false;
        {
            LOCK(cs_main);
            std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> >::iterator it = mapBlocksInFlight.find(resp.blockhash);
            if (it == mapBlocksInFlight.end() || !it->second.second->partialBlock ||