Re: [PATCH v7 17/26] rust: alloc: remove `VecExt` extension

Gary Guo
2024-09-28T19:29:26Z

On Thu, 12 Sep 2024 00:52:53 +0200
Danilo Krummrich <dakr@kernel.org> wrote:

> Now that all existing `Vec` users were moved to the kernel `Vec` type,
> remove the `VecExt` extension.
>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Reviewed-by: Benno Lossin <benno.lossin@proton.me>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
> rust/kernel/alloc.rs | 1 -
> rust/kernel/alloc/vec_ext.rs | 185 -----------------------------------
> rust/kernel/prelude.rs | 5 +-
> 3 files changed, 1 insertion(+), 190 deletions(-)
> delete mode 100644 rust/kernel/alloc/vec_ext.rs
>
> diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
> index e8fbae2adadb..aabdf80e4f7b 100644
> --- a/rust/kernel/alloc.rs
> +++ b/rust/kernel/alloc.rs
> @@ -6,7 +6,6 @@
> pub mod allocator;
> pub mod kbox;
> pub mod kvec;
> -pub mod vec_ext;
>
> #[cfg(any(test, testlib))]
> pub mod allocator_test;
> diff --git a/rust/kernel/alloc/vec_ext.rs b/rust/kernel/alloc/vec_ext.rs
> deleted file mode 100644
> index 1297a4be32e8..000000000000
> --- a/rust/kernel/alloc/vec_ext.rs
> +++ /dev/null
> @@ -1,185 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -
> -//! Extensions to [`Vec`] for fallible allocations.
> -
> -use super::{AllocError, Flags};
> -use alloc::vec::Vec;
> -
> -/// Extensions to [`Vec`].
> -pub trait VecExt<T>: Sized {
> - /// Creates a new [`Vec`] instance with at least the given capacity.
> - ///
> - /// # Examples
> - ///
> - /// ```
> - /// let v = Vec::<u32>::with_capacity(20, GFP_KERNEL)?;
> - ///
> - /// assert!(v.capacity() >= 20);
> - /// # Ok::<(), Error>(())
> - /// ```
> - fn with_capacity(capacity: usize, flags: Flags) -> Result<Self, AllocError>;
> -
> - /// Appends an element to the back of the [`Vec`] instance.
> - ///
> - /// # Examples
> - ///
> - /// ```
> - /// let mut v = Vec::new();
> - /// v.push(1, GFP_KERNEL)?;
> - /// assert_eq!(&v, &[1]);
> - ///
> - /// v.push(2, GFP_KERNEL)?;
> - /// assert_eq!(&v, &[1, 2]);
> - /// # Ok::<(), Error>(())
> - /// ```
> - fn push(&mut self, v: T, flags: Flags) -> Result<(), AllocError>;
> -
> - /// Pushes clones of the elements of slice into the [`Vec`] instance.
> - ///
> - /// # Examples
> - ///
> - /// ```
> - /// let mut v = Vec::new();
> - /// v.push(1, GFP_KERNEL)?;
> - ///
> - /// v.extend_from_slice(&[20, 30, 40], GFP_KERNEL)?;
> - /// assert_eq!(&v, &[1, 20, 30, 40]);
> - ///
> - /// v.extend_from_slice(&[50, 60], GFP_KERNEL)?;
> - /// assert_eq!(&v, &[1, 20, 30, 40, 50, 60]);
> - /// # Ok::<(), Error>(())
> - /// ```
> - fn extend_from_slice(&mut self, other: &[T], flags: Flags) -> Result<(), AllocError>
> - where
> - T: Clone;
> -
> - /// Ensures that the capacity exceeds the length by at least `additional` elements.
> - ///
> - /// # Examples
> - ///
> - /// ```
> - /// let mut v = Vec::new();
> - /// v.push(1, GFP_KERNEL)?;
> - ///
> - /// v.reserve(10, GFP_KERNEL)?;
> - /// let cap = v.capacity();
> - /// assert!(cap >= 10);
> - ///
> - /// v.reserve(10, GFP_KERNEL)?;
> - /// let new_cap = v.capacity();
> - /// assert_eq!(new_cap, cap);
> - ///
> - /// # Ok::<(), Error>(())
> - /// ```
> - fn reserve(&mut self, additional: usize, flags: Flags) -> Result<(), AllocError>;
> -}
> -
> -impl<T> VecExt<T> for Vec<T> {
> - fn with_capacity(capacity: usize, flags: Flags) -> Result<Self, AllocError> {
> - let mut v = Vec::new();
> - <Self as VecExt<_>>::reserve(&mut v, capacity, flags)?;
> - Ok(v)
> - }
> -
> - fn push(&mut self, v: T, flags: Flags) -> Result<(), AllocError> {
> - <Self as VecExt<_>>::reserve(self, 1, flags)?;
> - let s = self.spare_capacity_mut();
> - s[0].write(v);
> -
> - // SAFETY: We just initialised the first spare entry, so it is safe to increase the length
> - // by 1. We also know that the new length is <= capacity because of the previous call to
> - // `reserve` above.
> - unsafe { self.set_len(self.len() + 1) };
> - Ok(())
> - }
> -
> - fn extend_from_slice(&mut self, other: &[T], flags: Flags) -> Result<(), AllocError>
> - where
> - T: Clone,
> - {
> - <Self as VecExt<_>>::reserve(self, other.len(), flags)?;
> - for (slot, item) in core::iter::zip(self.spare_capacity_mut(), other) {
> - slot.write(item.clone());
> - }
> -
> - // SAFETY: We just initialised the `other.len()` spare entries, so it is safe to increase
> - // the length by the same amount. We also know that the new length is <= capacity because
> - // of the previous call to `reserve` above.
> - unsafe { self.set_len(self.len() + other.len()) };
> - Ok(())
> - }
> -
> - #[cfg(any(test, testlib))]
> - fn reserve(&mut self, additional: usize, _flags: Flags) -> Result<(), AllocError> {
> - Vec::reserve(self, additional);
> - Ok(())
> - }
> -
> - #[cfg(not(any(test, testlib)))]
> - fn reserve(&mut self, additional: usize, flags: Flags) -> Result<(), AllocError> {
> - let len = self.len();
> - let cap = self.capacity();
> -
> - if cap - len >= additional {
> - return Ok(());
> - }
> -
> - if core::mem::size_of::<T>() == 0 {
> - // The capacity is already `usize::MAX` for SZTs, we can't go higher.
> - return Err(AllocError);
> - }
> -
> - // We know cap is <= `isize::MAX` because `Layout::array` fails if the resulting byte size
> - // is greater than `isize::MAX`. So the multiplication by two won't overflow.
> - let new_cap = core::cmp::max(cap * 2, len.checked_add(additional).ok_or(AllocError)?);
> - let layout = core::alloc::Layout::array::<T>(new_cap).map_err(|_| AllocError)?;
> -
> - let (old_ptr, len, cap) = destructure(self);
> -
> - // We need to make sure that `ptr` is either NULL or comes from a previous call to
> - // `krealloc_aligned`. A `Vec<T>`'s `ptr` value is not guaranteed to be NULL and might be
> - // dangling after being created with `Vec::new`. Instead, we can rely on `Vec<T>`'s capacity
> - // to be zero if no memory has been allocated yet.
> - let ptr = if cap == 0 {
> - core::ptr::null_mut()
> - } else {
> - old_ptr
> - };
> -
> - // SAFETY: `ptr` is valid because it's either NULL or comes from a previous call to
> - // `krealloc_aligned`. We also verified that the type is not a ZST.
> - let new_ptr = unsafe { super::allocator::krealloc_aligned(ptr.cast(), layout, flags) };
> - if new_ptr.is_null() {
> - // SAFETY: We are just rebuilding the existing `Vec` with no changes.
> - unsafe { rebuild(self, old_ptr, len, cap) };
> - Err(AllocError)
> - } else {
> - // SAFETY: `ptr` has been reallocated with the layout for `new_cap` elements. New cap
> - // is greater than `cap`, so it continues to be >= `len`.
> - unsafe { rebuild(self, new_ptr.cast::<T>(), len, new_cap) };
> - Ok(())
> - }
> - }
> -}
> -
> -#[cfg(not(any(test, testlib)))]
> -fn destructure<T>(v: &mut Vec<T>) -> (*mut T, usize, usize) {
> - let mut tmp = Vec::new();
> - core::mem::swap(&mut tmp, v);
> - let mut tmp = core::mem::ManuallyDrop::new(tmp);
> - let len = tmp.len();
> - let cap = tmp.capacity();
> - (tmp.as_mut_ptr(), len, cap)
> -}
> -
> -/// Rebuilds a `Vec` from a pointer, length, and capacity.
> -///
> -/// # Safety
> -///
> -/// The same as [`Vec::from_raw_parts`].
> -#[cfg(not(any(test, testlib)))]
> -unsafe fn rebuild<T>(v: &mut Vec<T>, ptr: *mut T, len: usize, cap: usize) {
> - // SAFETY: The safety requirements from this function satisfy those of `from_raw_parts`.
> - let mut tmp = unsafe { Vec::from_raw_parts(ptr, len, cap) };
> - core::mem::swap(&mut tmp, v);
> -}
> diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
> index 80223cdaa485..07daccf6ca8e 100644
> --- a/rust/kernel/prelude.rs
> +++ b/rust/kernel/prelude.rs
> @@ -14,10 +14,7 @@
> #[doc(no_inline)]
> pub use core::pin::Pin;
>
> -pub use crate::alloc::{flags::*, vec_ext::VecExt, Box, KBox, KVBox, KVVec, KVec, VBox, VVec};
> -
> -#[doc(no_inline)]
> -pub use alloc::vec::Vec;
> +pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec};
>
> #[doc(no_inline)]
> pub use macros::{module, pin_data, pinned_drop, vtable, Zeroable};