@Override
  public void cacheBlock(BlockCacheKey cacheKey, Cacheable buf, boolean inMemory) {
    if (isMetaBlock(buf.getBlockType())) {
      super.cacheBlock(cacheKey, buf, inMemory);
    }
  }
Cache only index block with the specified name and buffer
@param cacheKey block's cache key
@param buf      block buffer
@param inMemory if block is in-memory
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/IndexOnlyLruBlockCache.java