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From:   Andreas Hindborg <nmi@metaspace.dk>
To:     y86-dev@protonmail.com
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?utf-8?Q?Bj=C3=B6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
        Alice Ryhl <alice@ryhl.io>, rust-for-linux@vger.kernel.org,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev,
        Alice Ryhl <aliceryhl@google.com>,
        Andreas Hindborg <a.hindborg@samsung.com>
Subject: Re: [PATCH v4 03/15] rust: sync: change error type of constructor
 functions
Date:   Mon, 03 Apr 2023 10:41:08 +0200
In-reply-to: <20230331215053.585759-4-y86-dev@protonmail.com>
Message-ID: <87y1n9jr1x.fsf@metaspace.dk>
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y86-dev@protonmail.com writes:

> From: Benno Lossin <y86-dev@protonmail.com>
>
> Change the error type of the constructors of `Arc` and `UniqueArc` to be
> `AllocError` instead of `Error`. This makes the API more clear as to
> what can go wrong when calling `try_new` or its variants.
>
> Signed-off-by: Benno Lossin <y86-dev@protonmail.com>
> Cc: Gary Guo <gary@garyguo.net>
> Cc: Andreas Hindborg <a.hindborg@samsung.com>
> Cc: Alice Ryhl <aliceryhl@google.com>
> ---

Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>

>  rust/kernel/sync/arc.rs | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index f2f1c83d72ba..aa7135f0f238 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -17,11 +17,11 @@
>
>  use crate::{
>      bindings,
> -    error::Result,
>      types::{ForeignOwnable, Opaque},
>  };
>  use alloc::boxed::Box;
>  use core::{
> +    alloc::AllocError,
>      marker::{PhantomData, Unsize},
>      mem::{ManuallyDrop, MaybeUninit},
>      ops::{Deref, DerefMut},
> @@ -149,7 +149,7 @@ unsafe impl<T: ?Sized + Sync + Send> Sync for Arc<T> {}
>
>  impl<T> Arc<T> {
>      /// Constructs a new reference counted instance of `T`.
> -    pub fn try_new(contents: T) -> Result<Self> {
> +    pub fn try_new(contents: T) -> Result<Self, AllocError> {
>          // INVARIANT: The refcount is initialised to a non-zero value.
>          let value = ArcInner {
>              // SAFETY: There are no safety requirements for this FFI call.
> @@ -469,7 +469,7 @@ pub struct UniqueArc<T: ?Sized> {
>
>  impl<T> UniqueArc<T> {
>      /// Tries to allocate a new [`UniqueArc`] instance.
> -    pub fn try_new(value: T) -> Result<Self> {
> +    pub fn try_new(value: T) -> Result<Self, AllocError> {
>          Ok(Self {
>              // INVARIANT: The newly-created object has a ref-count of 1.
>              inner: Arc::try_new(value)?,
> @@ -477,7 +477,7 @@ impl<T> UniqueArc<T> {
>      }
>
>      /// Tries to allocate a new [`UniqueArc`] instance whose contents are not initialised yet.
> -    pub fn try_new_uninit() -> Result<UniqueArc<MaybeUninit<T>>> {
> +    pub fn try_new_uninit() -> Result<UniqueArc<MaybeUninit<T>>, AllocError> {
>          Ok(UniqueArc::<MaybeUninit<T>> {
>              // INVARIANT: The newly-created object has a ref-count of 1.
>              inner: Arc::try_new(MaybeUninit::uninit())?,