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Thu, 30 Apr 2020 14:24:53 +0000 (UTC) Received: from horse.redhat.com (ovpn-115-229.rdu2.redhat.com [10.10.115.229]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6EB5F1C953; Thu, 30 Apr 2020 14:24:48 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id ED380223620; Thu, 30 Apr 2020 10:24:47 -0400 (EDT) Date: Thu, 30 Apr 2020 10:24:47 -0400 From: Vivek Goyal To: "Dr. David Alan Gilbert" Subject: Re: [PATCH] virtiofsd: Show submounts Message-ID: <20200430142447.GC260081@redhat.com> 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> <20200430142013.GI2874@work-vm> MIME-Version: 1.0 In-Reply-To: <20200430142013.GI2874@work-vm> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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=207.211.31.120; envelope-from=vgoyal@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/29 23:34:52 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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" On Thu, Apr 30, 2020 at 03:20:13PM +0100, Dr. David Alan Gilbert wrote: > * 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 t= he > > > > > daemon and *then* mount under the shared directory, the guest see= s 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/dgilbe= rt/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 P= ROPAGATION > > > / /dev/mapper/fedora_dgilbert--t580-root[/home/dgilbert/virtio-f= s/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 P= ROPAGATION > > > / /dev/mapper/fedora_dgilbert--t580-root[/home/dgilbert/virtio-f= s/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, t= hen > > inside guest we should see a mount point at /sysroot/tmp? >=20 > That findmnt is on the host. >=20 > > 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 workin= g > > 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. >=20 > Right, the guest just sees: >=20 > `-/sysroot myfs virtiof rw,relatime Aha.. we are on same page now. So we need to figure out what's needed to propagate mounts inside guest. And that's what Max is working on, I think.=20 Thanks Vivek