refactor: replace m_last_write with m_next_write

Co-Authored-By: l0rinc <pap.lorinc@gmail.com>

Author: andrewtoth

src/validation.cpp

@@ -2876,16 +2876,12 @@ bool Chainstate::FlushStateToDisk(
             }
         }
         const auto nNow{NodeClock::now()};
-        // Avoid writing/flushing immediately after startup.
-        if (m_last_write == decltype(m_last_write){}) {
-            m_last_write = nNow;
-        }
         // The cache is large and we're within 10% and 10 MiB of the limit, but we have time now (not in the middle of a block processing).
         bool fCacheLarge = mode == FlushStateMode::PERIODIC && cache_state >= CoinsCacheSizeState::LARGE;
         // The cache is over the limit, we have to write now.
         bool fCacheCritical = mode == FlushStateMode::IF_NEEDED && cache_state >= CoinsCacheSizeState::CRITICAL;
         // It's been a while since we wrote the block index and chain state to disk. Do this frequently, so we don't need to redownload or reindex after a crash.
-        bool fPeriodicWrite = mode == FlushStateMode::PERIODIC && nNow > m_last_write + DATABASE_WRITE_INTERVAL;
+        bool fPeriodicWrite = mode == FlushStateMode::PERIODIC && nNow >= m_next_write;
         // Combine all conditions that result in a write to disk.
         bool should_write = (mode == FlushStateMode::ALWAYS) || fCacheLarge || fCacheCritical || fPeriodicWrite || fFlushForPrune;
         // Write blocks, block index and best chain related state to disk.
@@ -2946,7 +2942,10 @@ bool Chainstate::FlushStateToDisk(
                     (uint64_t)coins_mem_usage,
                     (bool)fFlushForPrune);
             }
-            m_last_write = NodeClock::now();
+        }
+
+        if (should_write || m_next_write == NodeClock::time_point::max()) {
+            m_next_write = NodeClock::now() + DATABASE_WRITE_INTERVAL;
         }
     }
     if (full_flush_completed && m_chainman.m_options.signals) {

src/validation.h

@@ -803,7 +803,7 @@ class Chainstate
     void UpdateTip(const CBlockIndex* pindexNew)
         EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
-    NodeClock::time_point m_last_write{};
+    NodeClock::time_point m_next_write{NodeClock::time_point::max()};
 
     /**
      * In case of an invalid snapshot, rename the coins leveldb directory so