As stat(2) states on my system, there is a field st_blocks in struct stat, which represents

The actual number of blocks allocated for the file in 512-byte units. As short symbolic links are stored in the inode, this number may be zero.

For sparse files, this size may differ significantly from st_size (fileSize here), which represents apparent/logical/virtual file size.

st_size is needed for implementing a du-like utility.

Please bind this field too.