a8f62f50 - virtiofs: export filesystem tags through sysfs

Tue, 13 Feb 2024 00:11:48 +0000

virtiofs: export filesystem tags through sysfsThe virtiofs filesystem is mounted using a "tag" which is exported bythe virtiofs device: # mount -t virtiofs /mntThe virtiofs driver knows about all the available tags but these arecurrently not exported to user space.People have asked for these tags to be exported to user space. Mostrecently Lennart Poettering has asked for it as he wants to scan thetags and mount virtiofs automatically in certain cases.https://gitlab.com/virtio-fs/virtiofsd/-/issues/128This patch exports tags at /sys/fs/virtiofs//tag where N is the id ofthe virtiofs device. The filesystem tag can be obtained by reading this"tag" file.There is also a symlink at /sys/fs/virtiofs//device that points tothe 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 objectscan then be exposed in a kset at /sys/fs/virtiofs/. Note that virtio_fsobjects may live slightly longer than we wish for them to be exposed touserspace, so kobject_del() is called explicitly when the underlyingvirtio_device is removed. The virtio_fs object is freed when allreferences are dropped (e.g. active mounts) but disappears as soon asthe virtiofs device is gone.Originally-by: Vivek Goyal Signed-off-by: Stefan Hajnoczi Reviewed-by: Vivek Goyal Signed-off-by: Miklos Szeredi List of files: /linux-6.15/Documentation/ABI/testing/sysfs-fs-virtiofs

Changes in sysfs-fs-virtiofs

a8f62f50 - virtiofs: export filesystem tags through sysfs