[Virtio-fs] [PATCH] virtiofs: Export filesystem tags through sysfs

[German Maglione]

On Tue, Oct 10, 2023 at 8:38 PM Stefan Hajnoczi <stefanha at redhat.com> 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
> >
> > 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
>
> If you respin this series, please mention that the tag is available at
> KOBJ_BIND time, but not KOBJ_ADD. Just a sentence or two is enough to
> help someone trying to figure out how to use this new sysfs attr with
> udev.

Maybe it's also worth mention, that the tag file is created after a successful
probe, so the tag should be a valid one: non-empty and unique

>
> >
> > Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
> > ---
> >  fs/fuse/virtio_fs.c | 34 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
>
> Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>



-- 
German