private void addBlockToFreeListUnderLock(FreeList freeList, int headerIx, int ix) {
      CasLog.logAddToList(arenaIx, headerIx, ix, freeList.listHead);
      if (freeList.listHead >= 0) {
        int oldHeadOffset = offsetFromHeaderIndex(freeList.listHead);
        assert getPrevFreeListItem(oldHeadOffset) == -1;
        data.putInt(oldHeadOffset, headerIx);
      }
      int offset = offsetFromHeaderIndex(headerIx);
      data.putInt(offset, -1);
      data.putInt(offset + 4, freeList.listHead);
      freeList.listHead = headerIx;
    }
Unsets the headers (meaning this does not refer to a buffer).
llap-server/src/java/org/apache/hadoop/hive/llap/cache/BuddyAllocator.java