From: Danilo Krummrich <dakr@xxxxxxxxxx>
commit 93e602310f87b7b515b86a8f919cc0799387e5c3 upstream.
Currently, we can't implement `FromIterator`. There are a couple of
issues with this trait in the kernel, namely:
- Rust's specialization feature is unstable. This prevents us to
optimize for the special case where `I::IntoIter` equals `Vec`'s
`IntoIter` type.
- We also can't use `I::IntoIter`'s type ID either to work around this,
since `FromIterator` doesn't require this type to be `'static`.
- `FromIterator::from_iter` does return `Self` instead of
`Result<Self, AllocError>`, hence we can't properly handle allocation
failures.
- Neither `Iterator::collect` nor `FromIterator::from_iter` can handle
additional allocation flags.
Instead, provide `IntoIter::collect`, such that we can at least convert
`IntoIter` into a `Vec` again.
Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx>
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241004154149.93856-19-dakr@xxxxxxxxxx
[ Added newline in documentation, changed case of section to be
consistent with an existing one, fixed typo. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
rust/kernel/alloc/kvec.rs | 95 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 95 insertions(+)
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -692,6 +692,101 @@ pub struct IntoIter<T, A: Allocator> {
_p: PhantomData<A>,
}
+impl<T, A> IntoIter<T, A>
+where
+ A: Allocator,
+{
+ fn into_raw_parts(self) -> (*mut T, NonNull<T>, usize, usize) {
+ let me = ManuallyDrop::new(self);
+ let ptr = me.ptr;
+ let buf = me.buf;
+ let len = me.len;
+ let cap = me.layout.len();
+ (ptr, buf, len, cap)
+ }
+
+ /// Same as `Iterator::collect` but specialized for `Vec`'s `IntoIter`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// let v = kernel::kvec![1, 2, 3]?;
+ /// let mut it = v.into_iter();
+ ///
+ /// assert_eq!(it.next(), Some(1));
+ ///
+ /// let v = it.collect(GFP_KERNEL);
+ /// assert_eq!(v, [2, 3]);
+ ///
+ /// # Ok::<(), Error>(())
+ /// ```
+ ///
+ /// # Implementation details
+ ///
+ /// Currently, we can't implement `FromIterator`. There are a couple of issues with this trait
+ /// in the kernel, namely:
+ ///
+ /// - Rust's specialization feature is unstable. This prevents us to optimize for the special
+ /// case where `I::IntoIter` equals `Vec`'s `IntoIter` type.
+ /// - We also can't use `I::IntoIter`'s type ID either to work around this, since `FromIterator`
+ /// doesn't require this type to be `'static`.
+ /// - `FromIterator::from_iter` does return `Self` instead of `Result<Self, AllocError>`, hence
+ /// we can't properly handle allocation failures.
+ /// - Neither `Iterator::collect` nor `FromIterator::from_iter` can handle additional allocation
+ /// flags.
+ ///
+ /// Instead, provide `IntoIter::collect`, such that we can at least convert a `IntoIter` into a
+ /// `Vec` again.
+ ///
+ /// Note that `IntoIter::collect` doesn't require `Flags`, since it re-uses the existing backing
+ /// buffer. However, this backing buffer may be shrunk to the actual count of elements.
+ pub fn collect(self, flags: Flags) -> Vec<T, A> {
+ let old_layout = self.layout;
+ let (mut ptr, buf, len, mut cap) = self.into_raw_parts();
+ let has_advanced = ptr != buf.as_ptr();
+
+ if has_advanced {
+ // Copy the contents we have advanced to at the beginning of the buffer.
+ //
+ // SAFETY:
+ // - `ptr` is valid for reads of `len * size_of::<T>()` bytes,
+ // - `buf.as_ptr()` is valid for writes of `len * size_of::<T>()` bytes,
+ // - `ptr` and `buf.as_ptr()` are not be subject to aliasing restrictions relative to
+ // each other,
+ // - both `ptr` and `buf.ptr()` are properly aligned.
+ unsafe { ptr::copy(ptr, buf.as_ptr(), len) };
+ ptr = buf.as_ptr();
+
+ // SAFETY: `len` is guaranteed to be smaller than `self.layout.len()`.
+ let layout = unsafe { ArrayLayout::<T>::new_unchecked(len) };
+
+ // SAFETY: `buf` points to the start of the backing buffer and `len` is guaranteed to be
+ // smaller than `cap`. Depending on `alloc` this operation may shrink the buffer or leaves
+ // it as it is.
+ ptr = match unsafe {
+ A::realloc(Some(buf.cast()), layout.into(), old_layout.into(), flags)
+ } {
+ // If we fail to shrink, which likely can't even happen, continue with the existing
+ // buffer.
+ Err(_) => ptr,
+ Ok(ptr) => {
+ cap = len;
+ ptr.as_ptr().cast()
+ }
+ };
+ }
+
+ // SAFETY: If the iterator has been advanced, the advanced elements have been copied to
+ // the beginning of the buffer and `len` has been adjusted accordingly.
+ //
+ // - `ptr` is guaranteed to point to the start of the backing buffer.
+ // - `cap` is either the original capacity or, after shrinking the buffer, equal to `len`.
+ // - `alloc` is guaranteed to be unchanged since `into_iter` has been called on the original
+ // `Vec`.
+ unsafe { Vec::from_raw_parts(ptr, len, cap) }
+ }
+}
+
impl<T, A> Iterator for IntoIter<T, A>
where
A: Allocator,
Patches currently in stable-queue which might be from ojeda@xxxxxxxxxx are
queue-6.12/drm-panic-avoid-reimplementing-iterator-find.patch
queue-6.12/documentation-rust-add-coding-guidelines-on-lints.patch
queue-6.12/rust-provide-proper-code-documentation-titles.patch
queue-6.12/rust-alloc-make-allocator-module-public.patch
queue-6.12/rust-alloc-remove-vecext-extension.patch
queue-6.12/rust-alloc-implement-reallocfunc.patch
queue-6.12/rust-alloc-separate-aligned_size-from-krealloc_aligned.patch
queue-6.12/rust-enable-clippy-unnecessary_safety_comment-lint.patch
queue-6.12/rust-alloc-update-module-comment-of-alloc.rs.patch
queue-6.12/rust-kbuild-expand-rusttest-target-for-macros.patch
queue-6.12/rust-error-use-core-alloc-layouterror.patch
queue-6.12/rust-str-test-replace-alloc-format.patch
queue-6.12/loongarch-use-asm_reachable.patch
queue-6.12/rust-alloc-implement-allocator-for-kmalloc.patch
queue-6.12/rust-alloc-implement-collect-for-intoiter.patch
queue-6.12/rust-alloc-introduce-arraylayout.patch
queue-6.12/rust-alloc-implement-vmalloc-allocator.patch
queue-6.12/documentation-rust-discuss-in-the-guidelines.patch
queue-6.12/rust-error-check-for-config-test-in-error-name.patch
queue-6.12/rust-enable-clippy-ignored_unit_patterns-lint.patch
queue-6.12/rust-enable-clippy-unnecessary_safety_doc-lint.patch
queue-6.12/rust-alloc-add-box-to-prelude.patch
queue-6.12/kbuild-rust-remove-the-alloc-crate-and-globalalloc.patch
queue-6.12/rust-alloc-add-allocator-trait.patch
queue-6.12/rust-treewide-switch-to-our-kernel-box-type.patch
queue-6.12/rust-introduce-.clippy.toml.patch
queue-6.12/rust-alloc-rename-kernelallocator-to-kmalloc.patch
queue-6.12/rust-alloc-implement-cmalloc-in-module-allocator_test.patch
queue-6.12/drm-panic-allow-verbose-version-check.patch
queue-6.12/rust-map-__kernel_size_t-and-friends-also-to-usize-isize.patch
queue-6.12/rust-alloc-add-module-allocator_test.patch
queue-6.12/rust-replace-clippy-dbg_macro-with-disallowed_macros.patch
queue-6.12/rust-alloc-add-__gfp_nowarn-to-flags.patch
queue-6.12/rust-enable-clippy-s-check-private-items.patch
queue-6.12/rust-error-make-conversion-functions-public.patch
queue-6.12/rust-sort-global-rust-flags.patch
queue-6.12/rust-alloc-implement-contains-for-flags.patch
queue-6.12/rust-init-remove-unneeded.patch
queue-6.12/rust-use-custom-ffi-integer-types.patch
queue-6.12/rust-sync-remove-unneeded.patch
queue-6.12/rust-treewide-switch-to-the-kernel-vec-type.patch
queue-6.12/rust-alloc-implement-kvmalloc-allocator.patch
queue-6.12/drm-panic-correctly-indent-continuation-of-line-in-list-item.patch
queue-6.12/rust-alloc-implement-kernel-vec-type.patch
queue-6.12/rust-workqueue-remove-unneeded.patch
queue-6.12/rust-error-optimize-error-type-to-use-nonzero.patch
queue-6.12/drm-panic-remove-unnecessary-borrow-in-alignment_pattern.patch
queue-6.12/rust-alloc-remove-extension-of-std-s-box.patch
queue-6.12/rust-block-fix-formatting-in-gendisk-doc.patch
queue-6.12/rust-enable-rustdoc-unescaped_backticks-lint.patch
queue-6.12/rust-fix-size_t-in-bindgen-prototypes-of-c-builtins.patch
queue-6.12/rust-enable-clippy-undocumented_unsafe_blocks-lint.patch
queue-6.12/rust-alloc-add-vec-to-prelude.patch
queue-6.12/rust-alloc-implement-intoiterator-for-vec.patch
queue-6.12/rust-alloc-implement-kernel-box.patch
queue-6.12/drm-panic-remove-redundant-field-when-assigning-value.patch
queue-6.12/rust-types-avoid-repetition-in-as-from-bytes-impls.patch
queue-6.12/rust-start-using-the-attribute.patch
queue-6.12/drm-panic-allow-verbose-boolean-for-clarity.patch
queue-6.12/maintainers-add-entry-for-the-rust-alloc-module.patch
queue-6.12/rust-alloc-fix-arraylayout-allocations.patch
queue-6.12/drm-panic-prefer-eliding-lifetimes.patch
