refactor: Replace feeDelta by m_modified_fee

* feeDelta tracked the delta (to be applied on top of the actual fee)
* m_modified_fee tracks the actual fee with the delta included
* Instead of passing in the new total delta to the Updater, pass in by
  how much the total delta should be modified.

This is needed for the next commit, but makes sense on its own because
the same is done by UpdateDescendantState and UpdateAncestorState.

1 files changed, 10 insertions, 6 deletions

diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 65c8b4ea60..9f785d4115 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -14,6 +14,7 @@
 #include <policy/policy.h>
 #include <policy/settings.h>
 #include <reverse_iterator.h>
+#include <util/check.h>
 #include <util/moneystr.h>
 #include <util/system.h>
 #include <util/time.h>
@@ -82,6 +83,7 @@ CTxMemPoolEntry::CTxMemPoolEntry(const CTransactionRef& tx, CAmount fee,
       entryHeight{entry_height},
       spendsCoinbase{spends_coinbase},
       sigOpCost{sigops_cost},
+      m_modified_fee{nFee},
       lockPoints{lp},
       nSizeWithDescendants{GetTxSize()},
       nModFeesWithDescendants{nFee},
@@ -89,11 +91,11 @@ CTxMemPoolEntry::CTxMemPoolEntry(const CTransactionRef& tx, CAmount fee,
       nModFeesWithAncestors{nFee},
       nSigOpCostWithAncestors{sigOpCost} {}
 
-void CTxMemPoolEntry::UpdateFeeDelta(CAmount newFeeDelta)
+void CTxMemPoolEntry::UpdateModifiedFee(CAmount fee_diff)
 {
-    nModFeesWithDescendants += newFeeDelta - feeDelta;
-    nModFeesWithAncestors += newFeeDelta - feeDelta;
-    feeDelta = newFeeDelta;
+    nModFeesWithDescendants += fee_diff;
+    nModFeesWithAncestors += fee_diff;
+    m_modified_fee += fee_diff;
 }
 
 void CTxMemPoolEntry::UpdateLockPoints(const LockPoints& lp)
@@ -483,8 +485,10 @@ void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAnces
     // Update transaction for any feeDelta created by PrioritiseTransaction
     CAmount delta{0};
     ApplyDelta(entry.GetTx().GetHash(), delta);
+    // The following call to UpdateModifiedFee assumes no previous fee modifications
+    Assume(entry.GetFee() == entry.GetModifiedFee());
     if (delta) {
-        mapTx.modify(newit, [&delta](CTxMemPoolEntry& e) { e.UpdateFeeDelta(delta); });
+        mapTx.modify(newit, [&delta](CTxMemPoolEntry& e) { e.UpdateModifiedFee(delta); });
     }
 
     // Update cachedInnerUsage to include contained transaction's usage.
@@ -920,7 +924,7 @@ void CTxMemPool::PrioritiseTransaction(const uint256& hash, const CAmount& nFeeD
         delta += nFeeDelta;
         txiter it = mapTx.find(hash);
         if (it != mapTx.end()) {
-            mapTx.modify(it, [&delta](CTxMemPoolEntry& e) { e.UpdateFeeDelta(delta); });
+            mapTx.modify(it, [&nFeeDelta](CTxMemPoolEntry& e) { e.UpdateModifiedFee(nFeeDelta); });
             // Now update all ancestors' modified fees with descendants
             setEntries setAncestors;
             uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();