linux-kernel - Re: [PATCH 1/3] rust: add Aliased type

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Message-ID: <Z5KJrTG8PN-nRrLZ@tardis.local>
Date: Thu, 23 Jan 2025 10:25:49 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Christian Schrefl <chrisi.schrefl@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lee Jones <lee@...nel.org>, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Danilo Krummrich <dakr@...nel.org>
Subject: Re: [PATCH 1/3] rust: add Aliased type

On Thu, Jan 23, 2025 at 07:04:40PM +0100, Christian Schrefl wrote:
> Hi Boqun
> 
> On 23.01.25 6:56 PM, Boqun Feng wrote:
> > On Thu, Jan 23, 2025 at 11:21:23AM +0100, Christian Schrefl wrote:
> > [...]
> >>>> +
> >>>> +/// Stores a value that may be aliased.
> >>>> +///
> >>>> +/// This is similar to `Opaque<T>` but is guaranteed to contain valid data and will
> >>>> +/// Call the Drop implementation of T when dropped.
> >>>> +#[repr(transparent)]
> >>>> +pub struct Aliased<T> {
> >>>
> >>> As I already mentioned [1], the name `Aliased` is more reflecting the
> >>> fact that this wrapper will avoid generating the "noalias" attribute(?)
> >>> on the reference/pointer to the type rather than an intuitive idea about
> >>> "why or when do I need this". Moreover, I think the argument about the
> >>> naming of the counterpart in unstable Rust (UnsafePinned) makes sense to
> >>> me [2]: this type alone won't prevent `&mut Aliased` getting `swap`, and
> >>> it has to be used with `Pin`.
> >>>
> >>> Therefore, I think we should use a different name, perhaps
> >>> `(Always)Shared`, or just use `UnsafePinned`, or, as always, looking
> >>> fowards to a better name from anybody ;-)
> >>>
> >>> [1]: https://lore.kernel.org/rust-for-linux/Z407egxOy7oNLpq8@boqun-archlinux/
> >>> [2]: https://rust-lang.github.io/rfcs/3467-unsafe-pinned.html#naming
> >>
> >> I don't particularly care about the name, I mostly used aliased, because that's
> >> the name that Alice originally used.
> >>
> >> `(Always)Shared` seems confusing to me.
> >>
> >> I guess we can use `UnsafePinned`, but most people won't know what that means,
> > 
> > Hmm.. but doesn't `Aliased` have the same effect, i.e. most people won't
> > know what that means? Moreover, people who already knows `UnsafePinned`
> > will still take some time to realize "`Aliased` is actually
> > `UnsafePinned`
> 
> I guess I'll name it `UnsafePinned` then.
> 
> > 
> >> also I'm not sure if it's a good Idea to use the same name as a (future) 
> >> language type.
> > 
> > The benefit is that we won't re-invent the wheel since `UnsafePinned`
> > already does what `Aliased` does here. If we don't have a good name, we
> > should use the one that most people are already using. Honestly, at this
> > point, I think we should just use the unstable feature unsafe_pinned.
> 
> I think that's not implemented in rustc yet.
> At least no implementation is linked in the tracking issue:
> https://github.com/rust-lang/rust/issues/125735
> 
> Once that's implemented we can use a `cfg` to disable this 
> implementation on new versions that provide it.
> (Assuming we use the same API)
> 

Sounds good to me, thanks!

Regards,
Boqun

> > [...]
> 
> Cheers
> Christian