bug#51425: file-system: validate flags

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

Hi Tobias,

Tobias Geerinckx-Rice <me@tobias.gr> writes:

> Maxim,
>
> Maxim Cournoyer 写道：
>> Another thing that is tricky about options is that some of them are
>> only
>> really understood by the 'mount' command line utility, not the
>> 'mount'
>> system call such as used in our init RAM disk (both are thrown
>> together
>> in 'man 8 mount' without an easy way to discern them apart, IIRC).
>
> Aha!  Let me introduce you to the only slightly unfortunately named
> ‘man 2 mount’ instead.

Eh, I'm not sure why I hadn't thought about that myself, thank you!  It
makes sense after all -- one man page (2) documents the options for the
system call, the other one (8) for the command.

> The way mount(8) lumps both together is… I guess it's user-friendly —
> in a way? — but it leads to this total confusion about what's what.
> Think of flags as literal bit flags, mainly because they are.

Hehe.

> Guix does make the distinction.  It's the right call but it leads to a
> brief education moment the first time you encounter both fields.
>
> You're absolutely right that mount options OTOH are arbitrary strings.
> They can't and shouldn't be ‘validated’, but we don't currently
> mandate their stringiness, and should.

Makes sense.

Thank you!

Maxim