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Re: [PATCH] virtiofsd: Show submounts
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH] virtiofsd: Show submounts |
Date: |
Thu, 30 Apr 2020 15:34:25 +0100 |
User-agent: |
Mutt/1.13.3 (2020-01-12) |
On Thu, Apr 30, 2020 at 03:20:13PM +0100, Dr. David Alan Gilbert wrote:
> * Vivek Goyal (address@hidden) 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
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- Re: [Virtio-fs] [PATCH] virtiofsd: Show submounts, (continued)
- Re: [PATCH] virtiofsd: Show submounts, Dr. David Alan Gilbert, 2020/04/29
- Re: [PATCH] virtiofsd: Show submounts, Vivek Goyal, 2020/04/29
- Re: [PATCH] virtiofsd: Show submounts, Max Reitz, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Dr. David Alan Gilbert, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Max Reitz, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Max Reitz, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Vivek Goyal, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Dr. David Alan Gilbert, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Vivek Goyal, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts,
Daniel P . Berrangé <=
- Re: [PATCH] virtiofsd: Show submounts, Vivek Goyal, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Daniel P . Berrangé, 2020/04/30
- Re: [PATCH] virtiofsd: Show submounts, Vivek Goyal, 2020/04/30