Re: [PATCH v2] rust: Implement the smart pointer `InPlaceInit` for `Arc`

[Alex Mantel]

Submitted v3:

https://lore.kernel.org/rust-for-linux/20240727042442.682109-1-alexmantel93@xxxxxxxxxxx/

Thanks for the feedback!

On 25.07.24 11:06, Benno Lossin wrote:
> On 19.07.24 21:22, Alex Mantel wrote:
> > diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
> > index 68605b633..46f50cf12 100644
> > --- a/rust/kernel/init.rs
> > +++ b/rust/kernel/init.rs
> > @@ -213,6 +213,7 @@
> >   use crate::{
> >       alloc::{box_ext::BoxExt, AllocError, Flags},
> >       error::{self, Error},
> > +    sync::Arc,
> >       sync::UniqueArc,
> >       types::{Opaque, ScopeGuard},
> >   };
> > @@ -1112,11 +1113,15 @@ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
> >
> >   /// Smart pointer that can initialize memory in-place.
> >   pub trait InPlaceInit<T>: Sized {
> > +    /// A type might be pinned implicitly. An addtional `Pin<ImplicitlyPinned>` is useless. In
> > +    /// doubt, the type can just be set to `Pin<Self>`.
>
> This comment should better describe the purpose of this associated type,
> the first line could be "Pinned version of `Self`" then (with an empty
> line in between) you could write more explanatory stuff. I would also
> rephrase what you have above, for example: "If a type already implicitly
> pins its pointee, `Pin<Self>` is unnecessary. In this case use `Self`,
> otherwise just use `Pin<Self>`.".
>
> > +    type PinnedResult;
>
> I don't really like the name for this, since it is not a result. What do
> you think of `PinnedSelf`?
>
> Otherwise this looks good!
>
> ---
> Cheers,
> Benno
>
> > +
> >       /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
> >       /// type.
> >       ///
> >       /// If `T: !Unpin` it will not be able to move afterwards.
> > -    fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Pin<Self>, E>
> > +    fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedResult, E>
> >       where
> >           E: From<AllocError>;