[ISSUE]: Linux/pfsfuse & NBD - files don't finish transferring to PS2 until sync is ran

[bitrot-alpha]

Checks

• I have checked existing issues for duplicates and found none

Describe the issue

When copying multiple large files like PS1 VCDs over NBD using the Nautilus file manager in GNOME, the copy speed indicated is way too fast and really just false information. I've already tried using the mount options sync,direct_io to try and prevent write caching, which didn't seem to do anything. My last resort was to copy one file at a time and call sync after the file started copying.

Distro: OpenSUSE Tumbleweed
nbd-client version: 3.25
OPL (NBD server): 1.2.0 beta build 2016

Command I've been using: ./pfsfuse /dev/nbd4 ../ps2_hdd/ --partition=__.POPS -o allow_other,sync,direct_io

Similar issue in hdl-dump with a code example: ps2homebrew/hdl-dump#14

Console model

SCPH-39001