virtiofs: emit uevents on filesystem events

Alyssa Ross <[email protected]> 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 <[email protected]>
Reviewed-by: Vivek Goyal <[email protected]>
Signed-off-by: Miklos Szeredi <[email protected]>

0 files changed, 0 insertions, 0 deletions