But I'm not at all certain that (2) isn't a "no" and that efivarfs_pm_notify() can be called before a mount exists. IOW, once fsconfig(FSCONFIG_CMD_CREATE) is called the notifier seems ready and registered but userspace isn't forced to call fsmount(fd_fs) at all. They could just not to do it for whatever reason but the notifier should already be able to run. Another question is whether the superblock can be freed while efivarfs_pm_notify() is running? I think that can't happen because blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb) will block in efivarfs_kill_sb() until all outstanding calls to efivarfs_pm_notify() are finished? If (2) isn't guranteed then efivarfs_pm_notify() needs to be rewritten without relying on files because there's no guarantee that a mount exists at all.
