Status: It compiled.
Blkchnkr is a ublk server which creates a block device backed by an on demand allocated files.
$ blkchnkr init -r /tmp/repository --dev-id 42 --size 1t
[INFO] Created a new repository at /tmp/repository
# blkchnkr start -r /tmp/repository
[INFO] Starting up (v0.1.0)
[INFO] Created a new block device at /dev/ublkb42
[INFO] Ready!
# mkfs.xfs /dev/ublkb42
# mount --mkdir /dev/ublkb42 /tmp/mounted
$ cargo install --frozen --path .
# Development
$ cargo build --features debugGPL-3.0