On Thu, Feb 08, 2024 at 02:32:10PM -0500, Stefan Hajnoczi wrote: > The virtiofs filesystem is mounted using a "tag" which is exported by > the virtiofs device: > > # mount -t virtiofs <tag> /mnt > > The virtiofs driver knows about all the available tags but these are > currently not exported to user space. > > People have asked for 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 at /sys/fs/virtiofs/<N>/tag where N is the id of > the virtiofs device. The filesystem tag can be obtained by reading this > "tag" file. > > There is also a symlink at /sys/fs/virtiofs/<N>/device that points to > the virtiofs device that exports this tag. > > This patch converts the existing struct virtio_fs into a full kobject. > It already had a refcount so it's an easy change. The virtio_fs objects > can then be exposed in a kset at /sys/fs/virtiofs/. Note that virtio_fs > objects may live slightly longer than we wish for them to be exposed to > userspace, so kobject_del() is called explicitly when the underlying > virtio_device is removed. The virtio_fs object is freed when all > references are dropped (e.g. active mounts) but disappears as soon as > the virtiofs device is gone. > > Originally-by: Vivek Goyal <vgoyal@xxxxxxxxxx> > Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx> > --- > fs/fuse/virtio_fs.c | 113 ++++++++++++++++---- > Documentation/ABI/testing/sysfs-fs-virtiofs | 11 ++ > 2 files changed, 103 insertions(+), 21 deletions(-) > create mode 100644 Documentation/ABI/testing/sysfs-fs-virtiofs > > diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c > index de9a38efdf1e..28e96b7cde00 100644 > --- a/fs/fuse/virtio_fs.c > +++ b/fs/fuse/virtio_fs.c > @@ -31,6 +31,9 @@ > static DEFINE_MUTEX(virtio_fs_mutex); > static LIST_HEAD(virtio_fs_instances); > > +/* The /sys/fs/virtio_fs/ kset */ > +static struct kset *virtio_fs_kset; > + > enum { > VQ_HIPRIO, > VQ_REQUEST > @@ -55,7 +58,7 @@ struct virtio_fs_vq { > > /* A virtio-fs device instance */ > struct virtio_fs { > - struct kref refcount; > + struct kobject kobj; > struct list_head list; /* on virtio_fs_instances */ > char *tag; > struct virtio_fs_vq *vqs; > @@ -161,18 +164,43 @@ static inline void dec_in_flight_req(struct virtio_fs_vq *fsvq) > complete(&fsvq->in_flight_zero); > } > > -static void release_virtio_fs_obj(struct kref *ref) > +static ssize_t virtio_fs_tag_attr_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > { > - struct virtio_fs *vfs = container_of(ref, struct virtio_fs, refcount); > + struct virtio_fs *fs = container_of(kobj, struct virtio_fs, kobj); > + > + return sysfs_emit(buf, fs->tag); > +} > + > +static struct kobj_attribute virtio_fs_tag_attr = { > + .attr = { .name = "tag", .mode= 0644 }, > + .show = virtio_fs_tag_attr_show, > +}; __ATTR_RO()? That way we all know you got the mode setting correct :) Other than that minor thing, looks good, nice job! greg k-h
