notifier_list_notify() has no return value. This is fine when we just
want to invoke side-effects.
Sometimes it's useful for notifiers to produce a return value. This
allows notifiers to "veto" an operation and will be used by the block
layer before-write notifier.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
