On Tue, Mar 11, 2025 at 08:53:02PM +0100, David Hildenbrand wrote: > > 2. 9pfs seems to pass the f_type through from the host. So you can't > > detect it this way anyway. > > > > [3. I guess overlayfs & friends would also be an issue here although > > that doesn't affect my usecase.] > > > > Anyway, I think we would have to scrape /proc/mounts to do this :( > > > > The question I am asking myself: is this a 9pfs design bug or is it a 9pfs > hypervisor bug. Because we shouldn't try too hard to work around hypervisor > bugs. > > Which 9pfs implementation are you using in the hypervisor? I'm using QEMU via virtme-ng. IIUC virtme-ng knows how to use viortfs for the rootfs, but for individually-mounted directories with --rwdir/--rodir it uses 9pfs unconditionally. Even if it's a bug in QEMU, I think it is worth working around this one way or another. QEMU by far the most practical way to run these tests, and virtme-ng is probably the most popular/practical way to do that. I think even if we are confident it's just a bunch of broken code that isn't even in Linux, it's pragmatic to spend a certain amount of energy on having green tests there. (Also, this f_type thing might be totally intentional specified filesystem behaviour, I don't know).
