exception safety when writing block (#168)

* make sure we always clear writing block from m_ActiveWriteBlocks even if we have an exception

2 files changed, 9 insertions, 10 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index da6cd320d..f4c8a157a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 - Improvement: Refactored GCv2 to reduce time we block write requests, trading for longer overall GC time
   - Reduces time writes are blocked by ~8 times, going from 6s to 0.7s on a large data set
   - Increases time for GC to execute (without blocking reads/writes) by ~1.7 times, going from 10.4s to 17.6s on a large data set
+- Bugfix: Make sure we clear active write block if block store if we get exception when writing to disk
 
 ## 5.5.8
 - Feature: Added `zen cache-gen` command to generate large amount of cache data for testing
diff --git a/src/zenstore/blockstore.cpp b/src/zenstore/blockstore.cpp
index 00a38c3b6..7c6677052 100644
--- a/src/zenstore/blockstore.cpp
+++ b/src/zenstore/blockstore.cpp
@@ -539,16 +539,15 @@ BlockStore::WriteChunk(const void* Data, uint64_t Size, uint32_t Alignment, cons
 	Ref<BlockStoreFile> WriteBlock = m_WriteBlock;
 	m_ActiveWriteBlocks.push_back(WriteBlockIndex);
 	InsertLock.ReleaseNow();
+	auto _ = MakeGuard([this, WriteBlockIndex]() {
+		RwLock::ExclusiveLockScope _(m_InsertLock);
+		m_ActiveWriteBlocks.erase(std::find(m_ActiveWriteBlocks.begin(), m_ActiveWriteBlocks.end(), WriteBlockIndex));
+	});
 
 	WriteBlock->Write(Data, ChunkSize, AlignedInsertOffset);
 	m_TotalSize.fetch_add(AlignedWriteSize, std::memory_order::relaxed);
 
 	Callback({.BlockIndex = WriteBlockIndex, .Offset = AlignedInsertOffset, .Size = ChunkSize});
-
-	{
-		RwLock::ExclusiveLockScope _(m_InsertLock);
-		m_ActiveWriteBlocks.erase(std::find(m_ActiveWriteBlocks.begin(), m_ActiveWriteBlocks.end(), WriteBlockIndex));
-	}
 }
 
 void
@@ -615,6 +614,10 @@ BlockStore::WriteChunks(std::span<IoBuffer> Datas, uint32_t Alignment, const Wri
 		Ref<BlockStoreFile> WriteBlock = m_WriteBlock;
 		m_ActiveWriteBlocks.push_back(WriteBlockIndex);
 		InsertLock.ReleaseNow();
+		auto _ = MakeGuard([this, WriteBlockIndex]() {
+			RwLock::ExclusiveLockScope _(m_InsertLock);
+			m_ActiveWriteBlocks.erase(std::find(m_ActiveWriteBlocks.begin(), m_ActiveWriteBlocks.end(), WriteBlockIndex));
+		});
 
 		{
 			MutableMemoryView WriteBuffer(Buffer.data(), RangeSize);
@@ -639,11 +642,6 @@ BlockStore::WriteChunks(std::span<IoBuffer> Datas, uint32_t Alignment, const Wri
 		}
 		Callback(Locations);
 
-		{
-			RwLock::ExclusiveLockScope _(m_InsertLock);
-			m_ActiveWriteBlocks.erase(std::find(m_ActiveWriteBlocks.begin(), m_ActiveWriteBlocks.end(), WriteBlockIndex));
-		}
-
 		Offset += Count;
 	}
 }