Commit 2b34b287 authored Dec 02, 2024 by Shuai Wu

virtiofs: emit uevents on filesystem events

mainline inclusion
from mainline-v6.10
commit 9086b2d9e9f3da0b0f939aa1d7ff74e9bf5b54c8
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/IB81UH

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9086b2d9e9f3da0b0f939aa1d7ff74e9bf5b54c8



-------------------------------------------------

Alyssa Ross <hi@alyssa.is> requested that virtiofs notifies userspace
when filesytems become available. This can be used to detect when a
filesystem with a given tag is hotplugged, for example. uevents allow
userspace to detect changes without resorting to polling.

The tag is included as a uevent property so it's easy for userspace to
identify the filesystem in question even when the sysfs directory goes
away during removal.

Here are example uevents:

  # udevadm monitor -k -p

  KERNEL[111.113221] add      /fs/virtiofs/2 (virtiofs)
  ACTION=add
  DEVPATH=/fs/virtiofs/2
  SUBSYSTEM=virtiofs
  TAG=test

  KERNEL[165.527167] remove   /fs/virtiofs/2 (virtiofs)
  ACTION=remove
  DEVPATH=/fs/virtiofs/2
  SUBSYSTEM=virtiofs
  TAG=test

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Shuai Wu <wushuai51@huawei.com>

parent cc6009cb

fs/fuse/virtio_fs.c

+16 −1

Original line number	Diff line number	Diff line
		@@ -306,6 +306,8 @@ static int virtio_fs_add_instance(struct virtio_device *vdev,

		mutex_unlock(&virtio_fs_mutex);

		kobject_uevent(&fs->kobj, KOBJ_ADD);

		return 0;
		}

		@@ -1565,9 +1567,22 @@ static struct file_system_type virtio_fs_type = {
		.kill_sb = virtio_kill_sb,
		};

		static int virtio_fs_uevent(const struct kobject kobj, struct kobj_uevent_env env)
		{
		const struct virtio_fs *fs = container_of(kobj, struct virtio_fs, kobj);

		add_uevent_var(env, "TAG=%s", fs->tag);
		return 0;
		}

		static const struct kset_uevent_ops virtio_fs_uevent_ops = {
		.uevent = virtio_fs_uevent,
		};

		static int __init virtio_fs_sysfs_init(void)
		{
		virtio_fs_kset = kset_create_and_add("virtiofs", NULL, fs_kobj);
		virtio_fs_kset = kset_create_and_add("virtiofs", &virtio_fs_uevent_ops,
		fs_kobj);
		if (!virtio_fs_kset)
		return -ENOMEM;
		return 0;