On Thu, Apr 30, 2020 at 03:20:13PM +0100, Dr. David Alan Gilbert wrote: > * Vivek Goyal (vgo...@redhat.com) wrote: > > On Thu, Apr 30, 2020 at 09:58:12AM +0100, Dr. David Alan Gilbert wrote: > > [..] > > > > > Even without this patch, the SLAVE stuff worked so if you start the > > > > > daemon and *then* mount under the shared directory, the guest sees it > > > > > with or without this patch. > > > > > > > > Hm, I don’t. Do you really? > > > > > > Yes! With your patch reverted: > > > > > > Start virtiofsd, mount in the guest: > > > > > > host: > > > # ./virtiofsd --socket-path=/tmp/vhostqemu -o > > > source=/home/dgilbert/virtio-fs/fs -o log_level=warn -o no_writeback > > > > > > guest: > > > # mount -t virtiofs myfs /sysroot > > > > > > host: > > > # findmnt -o +PROPAGATION -N 6100 > > > TARGET SOURCE > > > FSTYPE OPTIONS > > > PROPAGATION > > > / > > > /dev/mapper/fedora_dgilbert--t580-root[/home/dgilbert/virtio-fs/fs] xfs > > > rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,no > > > private,slave > > > # mount -t tmpfs /dev/null /home/dgilbert/virtio-fs/fs/tmp > > > # findmnt -o +PROPAGATION -N 6100 > > > TARGET SOURCE > > > FSTYPE OPTIONS > > > PROPAGATION > > > / > > > /dev/mapper/fedora_dgilbert--t580-root[/home/dgilbert/virtio-fs/fs] xfs > > > rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,no > > > private,slave > > > └─/tmp /dev/null > > > tmpfs rw,relatime,seclabel > > > private,slave > > > > Why is it showing a mount point at "/tmp". If mount point propagated, then > > inside guest we should see a mount point at /sysroot/tmp? > > That findmnt is on the host. > > > So there are two things. > > > > A. Propagation of mount from host to virtiofsd. > > B. Visibility of that mount inside guest over fuse protocol (submount > > functionality). > > > > I think A works for me without any patches. But don't think B is working > > for me. I don't see the submount inside guest. > > > > > # touch /home/dgilbert/virtio-fs/fs/tmp/hello > > > > > > guest: > > > # ls -l /sysroot/tmp > > > total 0 > > > -rw-r--r-- 1 root root 0 Apr 30 08:50 hello > > > > Do a "findmnt /sysroot/tmp" inside guest and see what do you see. > > > > You will be able to see "hello" as long as virtiofsd sees the new > > mount point, I think. And guest does not have to see that mount point > > for this simple test to work. > > Right, the guest just sees: > > `-/sysroot myfs virtiof rw,relatime
That is a good thing surely ? If I'm exporting "/sysroot" from the host, I want the content in "/sysroot/some/sub/mount" to be visible to the guest, but I don't want the guest to see "/sysroot/some/sub/mount" as an actual mount point. That would be leaking information about the host storage setup into the guest. The host admin should be free to re-arrange submounts in the host OS, to bring more storage space online, and have this be transparent to the guest OS. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
