fileblock_t
fileblock_t logicalEndIndex
fileblock_t diff = index - extent.LogicalBlock();
ExtentStream::_Check(ext2_extent_stream *stream, fileblock_t &block)
fileblock_t index = offset >> fVolume->BlockShift();
fileblock_t block = 0;
status_t _Check(ext2_extent_stream *stream, fileblock_t &block);