Fix curruption of disk cache bucket index on GC (#448)

* make sure we hold the index lock when reading payload data in reclaim space
* don't use index snapshot when updating index in reclaim space
* check that things have not moved under our feet
* don't touch m_Payloads without a lock
* start write block index on the highest block index
* we don't need to bump writeblockindex when stopping write to a block, we will bump appropriately when we start a new block
* changelog

1 files changed, 7 insertions, 4 deletions

diff --git a/src/zenstore/blockstore.cpp b/src/zenstore/blockstore.cpp
index f99b0bc4a..968e919d6 100644
--- a/src/zenstore/blockstore.cpp
+++ b/src/zenstore/blockstore.cpp
@@ -171,6 +171,7 @@ BlockStore::Initialize(const std::filesystem::path& BlocksBasePath, uint64_t Max
 
 	if (std::filesystem::is_directory(m_BlocksBasePath))
 	{
+		uint32_t						   NextBlockIndex = 0;
 		std::vector<std::filesystem::path> FoldersToScan;
 		FoldersToScan.push_back(m_BlocksBasePath);
 		size_t FolderOffset = 0;
@@ -202,10 +203,15 @@ BlockStore::Initialize(const std::filesystem::path& BlocksBasePath, uint64_t Max
 					m_TotalSize.fetch_add(BlockFile->FileSize(), std::memory_order::relaxed);
 					m_ChunkBlocks[BlockIndex] = BlockFile;
 					FoundBlocks[BlockIndex]	  = BlockFile->FileSize();
+					if (BlockIndex >= NextBlockIndex)
+					{
+						NextBlockIndex = (BlockIndex + 1) & (m_MaxBlockCount - 1);
+					}
 				}
 			}
 			++FolderOffset;
 		}
+		m_WriteBlockIndex.store(NextBlockIndex, std::memory_order_release);
 	}
 	else
 	{
@@ -363,14 +369,11 @@ BlockStore::Flush(bool ForceNewBlock)
 		RwLock::ExclusiveLockScope _(m_InsertLock);
 		if (m_CurrentInsertOffset > 0)
 		{
-			uint32_t WriteBlockIndex = m_WriteBlockIndex.load(std::memory_order_acquire);
-			WriteBlockIndex			 = (WriteBlockIndex + 1) & (m_MaxBlockCount - 1);
 			if (m_WriteBlock)
 			{
 				m_WriteBlock->Flush();
 			}
-			m_WriteBlock = nullptr;
-			m_WriteBlockIndex.store(WriteBlockIndex, std::memory_order_release);
+			m_WriteBlock		  = nullptr;
 			m_CurrentInsertOffset = 0;
 		}
 		return;