From 5e4ac5abf54f8e6d6330df0c73119aa0cca4c103 Mon Sep 17 00:00:00 2001
From: Martin Leitner-Ankerl <martin.ankerl@gmail.com>
Date: Sat, 11 Jun 2022 11:00:53 +0200
Subject: [PATCH] Call ReallocateCache() on each Flush()

This frees up all associated memory with the map, not only the nodes.
This is necessary in preparation for using the PoolAllocator for
CCoinsMap, which does not actually free any memory on clear().
---
 src/coins.cpp                       | 9 ++++++---
 src/test/validation_flush_tests.cpp | 5 ++---
 src/validation.cpp                  | 1 -
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/coins.cpp b/src/coins.cpp
index 5a6ae525a7..f55932f302 100644
--- a/src/coins.cpp
+++ b/src/coins.cpp
@@ -253,9 +253,12 @@ bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn
 
 bool CCoinsViewCache::Flush() {
     bool fOk = base->BatchWrite(cacheCoins, hashBlock, /*erase=*/true);
-    if (fOk && !cacheCoins.empty()) {
-        /* BatchWrite must erase all cacheCoins elements when erase=true. */
-        throw std::logic_error("Not all cached coins were erased");
+    if (fOk) {
+        if (!cacheCoins.empty()) {
+            /* BatchWrite must erase all cacheCoins elements when erase=true. */
+            throw std::logic_error("Not all cached coins were erased");
+        }
+        ReallocateCache();
     }
     cachedCoinsUsage = 0;
     return fOk;
diff --git a/src/test/validation_flush_tests.cpp b/src/test/validation_flush_tests.cpp
index 26c48eb0e0..205164b94c 100644
--- a/src/test/validation_flush_tests.cpp
+++ b/src/test/validation_flush_tests.cpp
@@ -131,8 +131,7 @@ BOOST_AUTO_TEST_CASE(getcoinscachesizestate)
             CoinsCacheSizeState::OK);
     }
 
-    // Flushing the view doesn't take us back to OK because cacheCoins has
-    // preallocated memory that doesn't get reclaimed even after flush.
+    // Flushing the view does take us back to OK because ReallocateCache() is called
 
     BOOST_CHECK_EQUAL(
         chainstate.GetCoinsCacheSizeState(MAX_COINS_CACHE_BYTES, 0),
@@ -144,7 +143,7 @@ BOOST_AUTO_TEST_CASE(getcoinscachesizestate)
 
     BOOST_CHECK_EQUAL(
         chainstate.GetCoinsCacheSizeState(MAX_COINS_CACHE_BYTES, 0),
-        CoinsCacheSizeState::CRITICAL);
+        CoinsCacheSizeState::OK);
 }
 
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/validation.cpp b/src/validation.cpp
index e82fead89e..cf7688ea9f 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -4930,7 +4930,6 @@ bool Chainstate::ResizeCoinsCaches(size_t coinstip_size, size_t coinsdb_size)
     } else {
         // Otherwise, flush state to disk and deallocate the in-memory coins map.
         ret = FlushStateToDisk(state, FlushStateMode::ALWAYS);
-        CoinsTip().ReallocateCache();
     }
     return ret;
 }