Fix the wbcache dependency chain issue. (#291)

Add the dependency to any dirty buffer which has modification.
Either left or parent can be modified, add to the end of it.

conanfile.py

@@ -5,7 +5,7 @@
 
 class HomestoreConan(ConanFile):
     name = "homestore"
-    version = "5.0.5"
+    version = "5.0.6"
     homepage = "https://github.com/eBay/Homestore"
     description = "HomeStore Storage Engine"
     topics = ("ebay", "nublox")

src/lib/index/wb_cache.cpp

@@ -158,23 +158,26 @@ std::pair< bool, bool > IndexWBCache::create_chain(IndexBufferPtr& second, Index
     auto old_third = third;
     if (!second->is_clean()) {
         auto new_second = copy_buffer(second, cp_ctx);
+        chain = second;
         second = new_second;
         second_copied = true;
     }
 
     if (!third->is_clean()) {
         auto new_third = copy_buffer(third, cp_ctx);
+        chain = third;
         third = new_third;
         third_copied = true;
     }
 
     // Append parent(third) to the left child(second).
     second->m_next_buffer = third;
     third->m_wait_for_leaders.increment(1);
-    if (chain != second) {
+    if (second_copied || third_copied) {
         // We want buffers to be append to the end of the chain which are related.
         // If we split a node multiple times in same or different CP's, each dirty buffer will be
-        // added to the end of that chain.
+        // added to the end of that chain. Whichever dependent buffer is dirty, we add this
+        // parent-left combination to the end of that chain.
         while (chain->m_next_buffer.lock() != nullptr) {
             chain = chain->m_next_buffer.lock();
         }