Re: [PATCH v2] virtiofs: Export filesystem tags through sysfs

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Nov 08, 2023 at 04:33:33PM -0500, 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. Tag has a newline char at the end.
> 
> /sys/bus/virtio/devices/virtio<N>/tag
> 
> # cat /sys/bus/virtio/devices/virtio<N>/tag
> myfs
> 
> Note, tag is available at KOBJ_BIND time and not at KOBJ_ADD event time.
> 
> v2:
> - Add a newline char at the end in tag file. (Alyssa Ross)
> - Add a line in commit logs about tag file being available at KOBJ_BIND
>   time and not KOBJ_ADD time.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  fs/fuse/virtio_fs.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)

No documentation for your new sysfs file?  :(