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Message-ID: <ZgcBdlELp_5Stdxl@boqun-archlinux>
Date: Fri, 29 Mar 2024 10:59:18 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Wedson Almeida Filho <wedsonaf@...il.com>
Cc: rust-for-linux@...r.kernel.org, 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@...sung.com>,
Alice Ryhl <aliceryhl@...gle.com>, linux-kernel@...r.kernel.org,
Wedson Almeida Filho <walmeida@...rosoft.com>
Subject: Re: [PATCH v3 06/10] rust: alloc: introduce the `BoxExt` trait
On Wed, Mar 27, 2024 at 10:35:59PM -0300, Wedson Almeida Filho wrote:
> From: Wedson Almeida Filho <walmeida@...rosoft.com>
>
> Make fallible versions of `new` and `new_uninit` methods available in
> `Box` even though it doesn't implement them because we build `alloc`
> with the `no_global_oom_handling` config.
>
> They also have an extra `flags` parameter that allows callers to pass
> flags to the allocator.
>
> Signed-off-by: Wedson Almeida Filho <walmeida@...rosoft.com>
Reviewed-by: Boqun Feng <boqun.feng@...il.com>
A small nit below..
> ---
> rust/kernel/alloc.rs | 1 +
> rust/kernel/alloc/allocator.rs | 2 +-
> rust/kernel/alloc/box_ext.rs | 60 ++++++++++++++++++++++++++++++++++
> rust/kernel/init.rs | 13 ++++----
> rust/kernel/prelude.rs | 2 +-
> rust/kernel/sync/arc.rs | 3 +-
> 6 files changed, 72 insertions(+), 9 deletions(-)
> create mode 100644 rust/kernel/alloc/box_ext.rs
>
> diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
> index fd5541991a22..9bc1b48b5641 100644
> --- a/rust/kernel/alloc.rs
> +++ b/rust/kernel/alloc.rs
> @@ -5,6 +5,7 @@
> #[cfg(not(test))]
> #[cfg(not(testlib))]
> mod allocator;
> +pub mod box_ext;
> pub mod vec_ext;
>
> /// Flags to be used when allocating memory.
> diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
> index 8cc7099d6ae1..ff88bce04fd4 100644
> --- a/rust/kernel/alloc/allocator.rs
> +++ b/rust/kernel/alloc/allocator.rs
> @@ -16,7 +16,7 @@
> ///
> /// - `ptr` can be either null or a pointer which has been allocated by this allocator.
> /// - `new_layout` must have a non-zero size.
> -unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 {
> +pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 {
> // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
> let layout = new_layout.pad_to_align();
>
> diff --git a/rust/kernel/alloc/box_ext.rs b/rust/kernel/alloc/box_ext.rs
> new file mode 100644
> index 000000000000..c62db0aa4dd1
> --- /dev/null
> +++ b/rust/kernel/alloc/box_ext.rs
> @@ -0,0 +1,60 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Extensions to [`Box`] for fallible allocations.
> +
> +use super::Flags;
> +use alloc::boxed::Box;
> +use core::alloc::AllocError;
> +use core::mem::MaybeUninit;
> +use core::result::Result;
> +
> +/// Extensions to [`Box`].
> +pub trait BoxExt<T>: Sized {
> + /// Allocates a new box.
> + ///
> + /// The allocation may fail, in which case an error is returned.
> + fn new(x: T, flags: Flags) -> Result<Self, AllocError>;
> +
> + /// Allocates a new uninitialised box.
> + ///
> + /// The allocation may fail, in which case an error is returned.
> + fn new_uninit(flags: Flags) -> Result<Box<MaybeUninit<T>>, AllocError>;
> +}
> +
> +impl<T> BoxExt<T> for Box<T> {
> + fn new(x: T, flags: Flags) -> Result<Self, AllocError> {
> + let mut b = <Self as BoxExt<_>>::new_uninit(flags)?;
> + b.write(x);
> + // SAFETY: The contents were just initialised in the line above.
> + Ok(unsafe { b.assume_init() })
, since we have the new_uninit feature selected, we can actually do
fn new(x: T, flags: Flags) -> Result<Self, AllocError> {
<Self as BoxExt<_>>::new_uninit(flags).map(|b| Box::write(b, x))
}
here.
Regards,
Boqun
> + }
> +
[...]
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