[PATCH v10 6/8] rust: file: add `FileDescriptorReservation`

[Al Viro]

On Sun, Sep 15, 2024 at 11:01:26PM +0100, Al Viro wrote:

> There's not a lot of binary formats (5 of those currently -
> all in fs/binmt_*.c), but there's nothing to prohibit more
            binfmt_*.c, sorry.

> of them.  If somebody decides to add the infrastructure for
> writing those in Rust, begin_new_exec() wrapper will need
> to be documented as "never call that in scope of reserved
> descriptor".  Maybe by marking that wrapper unsafe and
> telling the users about the restriction wrt descriptor
> reservations, maybe by somehow telling the compiler to
> watch out for that - or maybe the constraint will be gone
> by that time.
> 
> In any case, the underlying constraint ("a thread with
> reserved descriptors should not try to get a private
> descriptor table until all those descriptors are disposed
> of one way or another") needs to be documented.
>