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@xxxxxxxxxx> > Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx> > --- > 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..9f76c9697e6f 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\n", fs->tag); > +} > +static DEVICE_ATTR_RO(tag); Is there a race between tag_show() and virtio_fs_remove()? virtio_fs_mutex is not held. I'm thinking of the case where userspace opens the sysfs file and invokes read(2) on one CPU while virtio_fs_remove() runs on another CPU. Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Attachment:
signature.asc
Description: PGP signature
