On Fri, Feb 09, 2024 at 10:36:47AM +0000, Greg KH wrote: > 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! Will fix, thanks! Stefan
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