[Virtio-fs] Live migration support for virtio-fs

[Dr. David Alan Gilbert]

* Ge, Xiongzi (Xiongzi.Ge at netapp.com) wrote:
> Hello Vivek, Dr. Gilbert, and the virtio-fs team,

Hi Xiongzi,

> It seems that virtio-fs does not support live migration. Once a vm
> is configured with virtio-fs, live migration cannot be performed even
> it is not mounted on the guest.

Right.

> Is there any progress for this?

Max Reitz is looking at some parts of it; in particular storing file
handles that can later be reopened.
But there are a bunch of other parts we've not looked at yet either
(like the dirty page marking around all syscalls).

> If the
> shared directory is from a distributed file system like Ceph, would it
> be easier than the general case to be implemented?

Maybe; there are some tricky semantics problems; for example, lets
imagine that you open the file   'a/b/c'  on the source, and sometime
after you open it, 'b' gets renamed to 'd';  when you resume on the
destination you need to make sure you know how to get to that file.
Depending on the filesystem semantics you might need to make that work
even if 'a/b/c' had been deleted but you still had it open.

Dave


> 
> Thanks,
> Xiongzi
> 
> 
-- 
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK