private void replaceListHeadUnderLock(FreeList freeList, int headerIx) {
      if (headerIx == freeList.listHead) return;
      if (headerIx >= 0) {
        int newHeadOffset = offsetFromHeaderIndex(headerIx);
        data.putInt(newHeadOffset, -1); // Remove backlink.
      }
      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