public synchronized int freeBlock(long offset, int length) {
    int bucketNo = (int) (offset / bucketCapacity);
    assert bucketNo >= 0 && bucketNo < buckets.length;
    Bucket targetBucket = buckets[bucketNo];
    bucketSizeInfos[targetBucket.sizeIndex()].freeBlock(targetBucket, offset, length);
    usedSize -= targetBucket.getItemAllocationSize();
    return targetBucket.getItemAllocationSize();
  }
Free a block with the offset
@param offset block's offset
@return size freed
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/BucketAllocator.java