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

[Stefan Hajnoczi]

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.

> 
> 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>
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