Reduce cs_main lock in ReadBlockFromDisk, only read GetBlockPos under the lock

Author: jonasschnelli

src/validation.cpp

@@ -1121,7 +1121,13 @@ bool ReadBlockFromDisk(CBlock& block, const CDiskBlockPos& pos, const Consensus:
 
 bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
 {
-    if (!ReadBlockFromDisk(block, pindex->GetBlockPos(), consensusParams))
+    CDiskBlockPos blockPos;
+    {
+        LOCK(cs_main);
+        blockPos = pindex->GetBlockPos();
+    }
+
+    if (!ReadBlockFromDisk(block, blockPos, consensusParams))
         return false;
     if (block.GetHash() != pindex->GetBlockHash())
         return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): GetHash() doesn't match index for %s at %s",

src/wallet/wallet.cpp

@@ -1689,13 +1689,8 @@ CBlockIndex* CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, CBlock
                 LogPrintf("Still rescanning. At block %d. Progress=%f\n", pindex->nHeight, GuessVerificationProgress(chainParams.TxData(), pindex));
             }
 
-            bool readRet = false;
             CBlock block;
-            {
-                LOCK(cs_main);
-                readRet = ReadBlockFromDisk(block, pindex, Params().GetConsensus());
-            }
-            if (readRet) {
+            if (ReadBlockFromDisk(block, pindex, Params().GetConsensus())) {
                 LOCK2(cs_main, cs_wallet);
                 if (pindex && !chainActive.Contains(pindex)) {
                     // Abort scan if current block is no longer active, to prevent