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Thu, 30 Apr 2020 14:20:22 +0000 (UTC) Received: from work-vm (ovpn-114-228.ams2.redhat.com [10.36.114.228]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8103C5D9C5; Thu, 30 Apr 2020 14:20:16 +0000 (UTC) Date: Thu, 30 Apr 2020 15:20:13 +0100 From: "Dr. David Alan Gilbert" To: Vivek Goyal Subject: Re: [PATCH] virtiofsd: Show submounts Message-ID: <20200430142013.GI2874@work-vm> References: <20200424133516.73077-1-mreitz@redhat.com> <20200427175902.GM2923@work-vm> <20200429145720.GA2835@work-vm> <8c73f374-fcc8-1684-b581-84a9ab501aa9@redhat.com> <20200430085812.GC2874@work-vm> <20200430135639.GA260081@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200430135639.GA260081@redhat.com> User-Agent: Mutt/1.13.4 (2020-02-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/30 01:31:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org, Stefan Hajnoczi , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Vivek Goyal (vgoyal@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. > > >=20 > > > Hm, I don=E2=80=99t. Do you really? > >=20 > > Yes! With your patch reverted: > >=20 > > Start virtiofsd, mount in the guest: > >=20 > > host: > > # ./virtiofsd --socket-path=3D/tmp/vhostqemu -o source=3D/home/dgilbert= /virtio-fs/fs -o log_level=3Dwarn -o no_writeback > >=20 > > guest: > > # mount -t virtiofs myfs /sysroot > >=20 > > host: > > # findmnt -o +PROPAGATION -N 6100 > > TARGET SOURCE = FSTYPE OPTIONS PRO= PAGATION > > / /dev/mapper/fedora_dgilbert--t580-root[/home/dgilbert/virtio-fs/= fs] xfs rw,relatime,seclabel,attr2,inode64,logbufs=3D8,logbsize=3D32k,no= private,slave > > # mount -t tmpfs /dev/null /home/dgilbert/virtio-fs/fs/tmp > > # findmnt -o +PROPAGATION -N 6100 > > TARGET SOURCE = FSTYPE OPTIONS PRO= PAGATION > > / /dev/mapper/fedora_dgilbert--t580-root[/home/dgilbert/virtio-fs/= fs] xfs rw,relatime,seclabel,attr2,inode64,logbufs=3D8,logbsize=3D32k,no= private,slave > > =E2=94=94=E2=94=80/tmp /dev/null = tmpfs rw,relatime,seclabel = private,slave >=20 > Why is it showing a mount point at "/tmp". If mount point propagated, the= n > inside guest we should see a mount point at /sysroot/tmp? That findmnt is on the host. > So there are two things. >=20 > A. Propagation of mount from host to virtiofsd. > B. Visibility of that mount inside guest over fuse protocol (submount > functionality). >=20 > 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.=20 >=20 > > # touch /home/dgilbert/virtio-fs/fs/tmp/hello > >=20 > > guest: > > # ls -l /sysroot/tmp > > total 0 > > -rw-r--r-- 1 root root 0 Apr 30 08:50 hello >=20 > Do a "findmnt /sysroot/tmp" inside guest and see what do you see. >=20 > 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 Dave > Vivek -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK