On Sat, Oct 21, 2023 at 04:10:21PM +0000, Alyssa Ross wrote: > On Thu, Oct 05, 2023 at 04:30:30PM -0400, Vivek Goyal wrote: > > virtiofs filesystem is mounted using a "tag" which is exported by the > > virtiofs device. virtiofs driver knows about all the available tags but > > these are not exported to user space. > > > > People have asked these tags to be exported to user space. Most recently > > Lennart Poettering has asked for it as he wants to scan the tags and mount > > virtiofs automatically in certain cases. > > > > https://gitlab.com/virtio-fs/virtiofsd/-/issues/128 > > Hi, I was one of those people. :) Hi Alyssa, Aha... Thanks. I was not able to remember who had requested this. > > > This patch exports tags through sysfs. One tag is associated with each > > virtiofs device. A new "tag" file appears under virtiofs device dir. > > Actual filesystem tag can be obtained by reading this "tag" file. > > > > For example, if a virtiofs device exports tag "myfs", a new file "tag" > > will show up here. > > > > /sys/bus/virtio/devices/virtio<N>/tag > > > > # cat /sys/bus/virtio/devices/virtio<N>/tag > > myfs > > > > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx> > > Are you still thinking about exposing this in the uevent as well? > That would be much more convenient for me, because with this approach > by the time the "remove" uevent arrives, it's no longer possible to > check what tag was associated with the device — you have to store it > somewhere when the device appears, so you can look it up again when the > device is removed. (Not everybody uses udev.) Looks like systemd + udev combination can already take care of it. I just had to specify "StopWhenUnneeded=true" in my systemd .mount unit file. And that made sure that when device goes away, virtiofs is unmounted and service is deactivated. Following is my mount unit file. $ cat /etc/systemd/system/mnt-virtiofs.mount [Unit] Description=Virtiofs mount myfs DefaultDependencies=no ConditionPathExists=/mnt/virtiofs ConditionCapability=CAP_SYS_ADMIN Before=sysinit.target StopWhenUnneeded=true [Mount] What=myfs Where=/mnt/virtiofs Type=virtiofs And following is the udev rule I used. $ cat /etc/udev/rules.d/80-local.rules SUBSYSTEM=="virtio", DRIVER=="virtiofs", ATTR{tag}=="myfs", TAG+="systemd", ENV{SYSTEMD_WANTS}+="mnt-virtiofs.mount" And a combination of above two seems to work. virtiofs is automatically mounted when device is hotplugged and it is unmounted when device is hot unplugged. > > Regardless, > > Tested-by: Alyssa Ross <hi@xxxxxxxxx> > > … and a review comment below. > > > --- > > fs/fuse/virtio_fs.c | 34 ++++++++++++++++++++++++++++++++++ > > 1 file changed, 34 insertions(+) > > > > diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c > > index 5f1be1da92ce..a5b11e18f331 100644 > > --- a/fs/fuse/virtio_fs.c > > +++ b/fs/fuse/virtio_fs.c > > @@ -107,6 +107,21 @@ static const struct fs_parameter_spec virtio_fs_parameters[] = { > > {} > > }; > > > > +/* Forward Declarations */ > > +static void virtio_fs_stop_all_queues(struct virtio_fs *fs); > > + > > +/* sysfs related */ > > +static ssize_t tag_show(struct device *dev, struct device_attribute *attr, > > + char *buf) > > +{ > > + struct virtio_device *vdev = container_of(dev, struct virtio_device, > > + dev); > > + struct virtio_fs *fs = vdev->priv; > > + > > + return sysfs_emit(buf, "%s", fs->tag); > > All of the other files in the device directory end with trailing > newlines. Should this one be an exception? I did not think much about it but you are right that other files seem to have a newline at the end. I will add one as well. Thanks Vivek
