Re: [Qemu-devel] [PATCH v7 0/3] 9p: Fix file ID collisions

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

On Dienstag, 8. Oktober 2019 11:14:59 CEST Greg Kurz wrote:
> > No, it is not a feature. It is still a fix. :) I cannot use 9p without
> > this
> > fix at all, so it is not some optional "feature" for me.
> 
> I understand your need but this is still arguable. The 9p device has
> a limitation with cross-device setups. The actual bug is to silently
> cause inode number collisions in the guest. This is partly fixed by the
> "9p: Treat multiple devices on one export as an error" patch. Thinking
> again, it would even make sense to move "remap" from "9p: Added virtfs
> option 'multidevs=remap|forbid|warn'" to its own patch. We could then
> consider that the bug is fully fixed with "multidevs=forbid|warn".
> 
> Then comes the "remap" feature which is expected to lift the limitation
> with cross-device setups, with a "not yet determined" performance cost
> and light reviewing of the code.

Are these patch transfer requests addressed at me to be done?

> Also, I strongly recommend you try out "virtio-fs" which is
> going to be soon the production grade way of sharing files
> between host and guest.
> 
> https://www.mail-archive.com/libvir-list@redhat.com/msg182457.html

Yes I know, I am following the development of virtio-fs already of course. 
However for me it is far too early to actually use it in a production 
environment. It e.g. seems to require bleeding edge kernel versions. And the 
real argument for switching from 9p to virtio-fs would be a significant 
performance increase. However so far (correct me if I am wrong) I have not 
seen benchmarks that would show that this was already the case (yet).

I wonder though whether virtio-fs suffers from the same file ID collisions 
problem when sharing multiple file systems.

What is your long-term plan for 9p? Will it be dropped completely after 
virtio-fs became stable?

Best regards,
Christian Schoenebeck