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Date: Tue, 26 Mar 2024 15:27:18 +0000
To: Wedson Almeida Filho <wedsonaf@gmail.com>
From: Benno Lossin <benno.lossin@proton.me>
Cc: rust-for-linux@vger.kernel.org, Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@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>, Andreas Hindborg <a.hindborg@samsung.com>, Alice Ryhl <aliceryhl@google.com>, linux-kernel@vger.kernel.org, Wedson Almeida Filho <walmeida@microsoft.com>
Subject: Re: [PATCH 10/10] rust: kernel: remove usage of `allocator_api` unstable feature
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On 25.03.24 20:54, Wedson Almeida Filho wrote:
> From: Wedson Almeida Filho <walmeida@microsoft.com>
>=20
> With the adoption of `BoxExt` and `VecExt`, we don't need the functions
> provided by this feature (namely the methods prefixed with `try_` and
> different allocator per collection instance).
>=20
> We do need `AllocError`, but we define our own as it is a trivial empty
> struct.
>=20
> Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
> ---
>  rust/kernel/alloc.rs        |  3 +++
>  rust/kernel/alloc/boxext.rs |  3 +--
>  rust/kernel/alloc/vecext.rs |  4 ++--
>  rust/kernel/error.rs        | 13 ++-----------
>  rust/kernel/init.rs         |  3 +--
>  rust/kernel/lib.rs          |  1 -
>  rust/kernel/str.rs          |  3 +--
>  rust/kernel/sync/arc.rs     |  4 ++--
>  rust/kernel/workqueue.rs    |  3 +--
>  9 files changed, 13 insertions(+), 24 deletions(-)
>=20
> diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
> index 5712c81b1308..f17f48130f13 100644
> --- a/rust/kernel/alloc.rs
> +++ b/rust/kernel/alloc.rs
> @@ -8,6 +8,9 @@
>  pub mod boxext;
>  pub mod vecext;
>=20
> +/// Indicates an allocation error.
> +pub struct AllocError;

I think it would be sensible to add this now:
    #[derive(Copy, Clone, PartialEq, Eq, Debug)]

> +
>  /// Flags to be used when allocating memory.
>  ///
>  /// They can be combined with the operators `|`, `&`, and `!`.
> diff --git a/rust/kernel/alloc/boxext.rs b/rust/kernel/alloc/boxext.rs
> index 26a918df7acf..3cdda0f635a3 100644
> --- a/rust/kernel/alloc/boxext.rs
> +++ b/rust/kernel/alloc/boxext.rs
> @@ -2,9 +2,8 @@
>=20
>  //! Extensions to [`Box`] for fallible allocations.
>=20
> -use super::Flags;
> +use super::{AllocError, Flags};
>  use alloc::boxed::Box;
> -use core::alloc::AllocError;
>  use core::mem::MaybeUninit;
>  use core::result::Result;
>=20
> diff --git a/rust/kernel/alloc/vecext.rs b/rust/kernel/alloc/vecext.rs
> index 1d4d51b45a49..85ca6a6db6de 100644
> --- a/rust/kernel/alloc/vecext.rs
> +++ b/rust/kernel/alloc/vecext.rs
> @@ -2,8 +2,8 @@
>=20
>  //! Extensions to [`Vec`] for fallible allocations.
>=20
> -use super::Flags;
> -use alloc::{alloc::AllocError, vec::Vec};
> +use super::{AllocError, Flags};
> +use alloc::vec::Vec;
>  use core::{mem::ManuallyDrop, result::Result};
>=20
>  /// Extensions to [`Vec`].
> diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
> index 4786d3ee1e92..fc986bc24c6d 100644
> --- a/rust/kernel/error.rs
> +++ b/rust/kernel/error.rs
> @@ -4,12 +4,9 @@
>  //!
>  //! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/=
uapi/asm-generic/errno-base.h)
>=20
> -use crate::str::CStr;
> +use crate::{alloc::AllocError, str::CStr};
>=20
> -use alloc::{
> -    alloc::{AllocError, LayoutError},
> -    collections::TryReserveError,
> -};
> +use alloc::alloc::LayoutError;
>=20
>  use core::convert::From;
>  use core::fmt;
> @@ -192,12 +189,6 @@ fn from(_: Utf8Error) -> Error {
>      }
>  }
>=20
> -impl From<TryReserveError> for Error {
> -    fn from(_: TryReserveError) -> Error {
> -        code::ENOMEM
> -    }
> -}
> -

Why are you removing this?

--=20
Cheers,
Benno

>  impl From<LayoutError> for Error {
>      fn from(_: LayoutError) -> Error {
>          code::ENOMEM
> diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
> index 1a8b0464db0c..1f7a6b5892ac 100644
> --- a/rust/kernel/init.rs
> +++ b/rust/kernel/init.rs
> @@ -211,14 +211,13 @@
>  //! [`pin_init!`]: crate::pin_init!
>=20
>  use crate::{
> -    alloc::{boxext::BoxExt, Flags},
> +    alloc::{boxext::BoxExt, AllocError, Flags},
>      error::{self, Error},
>      sync::UniqueArc,
>      types::{Opaque, ScopeGuard},
>  };
>  use alloc::boxed::Box;
>  use core::{
> -    alloc::AllocError,
>      cell::UnsafeCell,
>      convert::Infallible,
>      marker::PhantomData,
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 51f30e55bd00..5c641233e26d 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -12,7 +12,6 @@
>  //! do so first instead of bypassing this crate.
>=20
>  #![no_std]
> -#![feature(allocator_api)]
>  #![feature(coerce_unsized)]
>  #![feature(dispatch_from_dyn)]
>  #![feature(new_uninit)]
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index 34dbc85b5220..5206b18f882b 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -2,8 +2,7 @@
>=20
>  //! String representations.
>=20
> -use crate::alloc::{flags::*, vecext::VecExt};
> -use alloc::alloc::AllocError;
> +use crate::alloc::{flags::*, vecext::VecExt, AllocError};
>  use alloc::vec::Vec;
>  use core::fmt::{self, Write};
>  use core::ops::{self, Deref, Index};
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index af539c5eb4bc..8db25f73b37f 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -16,7 +16,7 @@
>  //! [`Arc`]: https://doc.rust-lang.org/std/sync/struct.Arc.html
>=20
>  use crate::{
> -    alloc::{boxext::BoxExt, Flags},
> +    alloc::{boxext::BoxExt, AllocError, Flags},
>      bindings,
>      error::{self, Error},
>      init::{self, InPlaceInit, Init, PinInit},
> @@ -25,7 +25,7 @@
>  };
>  use alloc::boxed::Box;
>  use core::{
> -    alloc::{AllocError, Layout},
> +    alloc::Layout,
>      fmt,
>      marker::{PhantomData, Unsize},
>      mem::{ManuallyDrop, MaybeUninit},
> diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> index 09a0f158ff1b..50837e56efc7 100644
> --- a/rust/kernel/workqueue.rs
> +++ b/rust/kernel/workqueue.rs
> @@ -132,9 +132,8 @@
>  //!
>  //! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqu=
eue.h)
>=20
> -use crate::alloc::Flags;
> +use crate::alloc::{AllocError, Flags};
>  use crate::{bindings, prelude::*, sync::Arc, sync::LockClassKey, types::=
Opaque};
> -use alloc::alloc::AllocError;
>  use alloc::boxed::Box;
>  use core::marker::PhantomData;
>  use core::pin::Pin;
> --
> 2.34.1
>