3 files changed, 30 insertions, 2 deletions
diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index 14a990131..b3096e473 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -126,7 +126,7 @@ static const uint64_t testnet_hard_fork_version_1_till = 624633;
 //------------------------------------------------------------------
 Blockchain::Blockchain(tx_memory_pool& tx_pool) :
   m_db(), m_tx_pool(tx_pool), m_hardfork(NULL), m_timestamps_and_difficulties_height(0), m_current_block_cumul_sz_limit(0),
-  m_enforce_dns_checkpoints(false), m_max_prepare_blocks_threads(4), m_db_blocks_per_sync(1), m_db_sync_mode(db_async), m_fast_sync(true), m_show_time_stats(false), m_sync_counter(0), m_cancel(false)
+  m_enforce_dns_checkpoints(false), m_max_prepare_blocks_threads(4), m_db_blocks_per_sync(1), m_db_sync_mode(db_async), m_db_default_sync(false), m_fast_sync(true), m_show_time_stats(false), m_sync_counter(0), m_cancel(false)
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
 }
@@ -4034,12 +4034,29 @@ bool Blockchain::for_all_txpool_txes(std::function<bool(const crypto::hash&, con
 
 void Blockchain::set_user_options(uint64_t maxthreads, uint64_t blocks_per_sync, blockchain_db_sync_mode sync_mode, bool fast_sync)
 {
+  if (sync_mode == db_defaultsync)
+  {
+    m_db_default_sync = true;
+    sync_mode = db_async;
+  }
   m_db_sync_mode = sync_mode;
   m_fast_sync = fast_sync;
   m_db_blocks_per_sync = blocks_per_sync;
   m_max_prepare_blocks_threads = maxthreads;
 }
 
+void Blockchain::safesyncmode(const bool onoff)
+{
+  /* all of this is no-op'd if the user set a specific
+   * --db-sync-mode at startup.
+   */
+  if (m_db_default_sync)
+  {
+    m_db->safesyncmode(onoff);
+    m_db_sync_mode = onoff ? db_nosync : db_async;
+  }
+}
+
 HardFork::State Blockchain::get_hard_fork_state() const
 {
   return m_hardfork->get_state();
diff --git a/src/cryptonote_core/blockchain.h b/src/cryptonote_core/blockchain.h
index 7fa78584b..b8ea657b4 100644
--- a/src/cryptonote_core/blockchain.h
+++ b/src/cryptonote_core/blockchain.h
@@ -65,6 +65,7 @@ namespace cryptonote
    */
   enum blockchain_db_sync_mode
   {
+    db_defaultsync, //!< user didn't specify, use db_async
     db_sync,  //!< handle syncing calls instead of the backing db, synchronously
     db_async, //!< handle syncing calls instead of the backing db, asynchronously
     db_nosync //!< Leave syncing up to the backing db (safest, but slowest because of disk I/O)
@@ -701,6 +702,11 @@ namespace cryptonote
         blockchain_db_sync_mode sync_mode, bool fast_sync);
 
     /**
+     * @brief Put DB in safe sync mode
+     */
+    void safesyncmode(const bool onoff);
+
+    /**
      * @brief set whether or not to show/print time statistics
      *
      * @param stats the new time stats setting
@@ -932,6 +938,7 @@ namespace cryptonote
     blockchain_db_sync_mode m_db_sync_mode;
     bool m_fast_sync;
     bool m_show_time_stats;
+    bool m_db_default_sync;
     uint64_t m_db_blocks_per_sync;
     uint64_t m_max_prepare_blocks_threads;
     uint64_t m_fake_pow_calc_time;
diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index 314f37246..a002f19a3 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -316,7 +316,7 @@ namespace cryptonote
 
     const std::string filename = folder.string();
     // default to fast:async:1
-    blockchain_db_sync_mode sync_mode = db_async;
+    blockchain_db_sync_mode sync_mode = db_defaultsync;
     uint64_t blocks_per_sync = 1;
 
     try
@@ -349,11 +349,15 @@ namespace cryptonote
           sync_mode = db_nosync;
         }
         else if(options[0] == "fast")
+        {
           db_flags = DBF_FAST;
+          sync_mode = db_async;
+        }
         else if(options[0] == "fastest")
         {
           db_flags = DBF_FASTEST;
           blocks_per_sync = 1000; // default to fastest:async:1000
+          sync_mode = db_async;
         }
         else
           db_flags = DEFAULT_FLAGS;