Further filesystems to ignore #3
Description
When overlaying things, further filesystem types should be ignored as accessing them may have externally visible state. In particular when ignoring nsfs you might also want to ignore cifs for the same reason you ignored nsfs.
Another category of filesystems to ignore covers everything related to FUSE, as even just reading such filesystems may by the very nature of FUSE have any effect you can think of. While usually FUSE is modelled to behave like normal, local filesystems do, there are several remote ones like sshfs, curlftpfs, et.al. that could create externally visible side-effects.
In general it might be worth noting that an allowlist for filesystems might be easier to maintain; possibly using an user-configuration.