virtio-fs doesn't aware modified unless refresh

[fecet]

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Describe the bug

After modify file system on host, windows guest have to refresh to know that.

To Reproduce Steps to reproduce the behaviour:

Write something on host

Expected behavior A clear and concise description of what you expected to happen.

Changes happen on guest as soon as host

Screenshots

Host:

• Disto: Ubuntu
• Kernel version: 5.0.4
• QEMU version 7.0
• QEMU command line start by virt-manager
• libvirt version 8.6
• libvirt XML file

VM:

• Windows 10
• virtiofs
• 1.229

Additional context Add any other context about the problem here.

[viktor-prutyanov]

Hi @fecet,

Windows Explorer shows a state as of the most recent ReadDirectory return. But any new request to FS will work with an updated state.

From an architectural point of view, Explorer can show an updated state with ReadDirectoryChangesW, but in the virtiofs service it requires a processing of the notify VirtIO queue. Also I'm not sure that WinFsp has full support of such FS to kernel notify logic.

To sum up, this is hypothetically feasible, but requires a lot of investigation and development. I'm not sure this is a good investment of time for just seeing host updates in Explorer.

[fecet]

of course we dont care Explorer but for some reason I need to modify file on host and watch the changes in guest. Maybe watching file soulds like a interesting feature good to consider.

My current solution is share smb from guest, it's really slow

[viktor-prutyanov]

All changes are seen on the guest side

[viktor-prutyanov]

Explorer simply doesn't show them

[fecet]

So it's perhaps beeter to be a FR, add watching file support for guest

[viktor-prutyanov]

OK, so let's reopen it and mark it as a feature request.