IOReadBandwidthMax with path says "Path ... is not a device file in /dev"

[rwmjones]

systemd version the issue has been seen with

systemd-238-9.git0e0aa59.fc28.x86_64

Used distribution

Fedora

Expected behaviour you didn't see

IOReadBandwidthMax is supposed to work with a path, but does not.

Unexpected behaviour you saw

An error instead of working

Steps to reproduce the problem

$ systemd-run --user --pipe -p IOReadBandwidthMax="/var/tmp 1K" echo hello
Failed to start transient service unit: Path IOReadBandwidthMax specified in /var/tmp= is not a device file in /dev

[yuwata]

I think this is already fixed by the commit 9d5e9b4, which is included in v239.