From ab309b6e084c70a29f9fa3cee797572bd2340901 Mon Sep 17 00:00:00 2001
From: Miguel Ojeda <ojeda@kernel.org>
Date: Wed, 4 Sep 2024 16:42:29 +0200
Subject: [PATCH] rust: avoid `box_uninit_write` feature
Like commit 0903b9e2a46c ("rust: alloc: eschew
`Box<MaybeUninit<T>>::write`"), but for the new `rbtree` and `alloc` code.
That is, `feature(new_uninit)` [1] got partially stabilized [2]
for Rust 1.82.0 (expected to be released on 2024-10-17), but it
did not include `Box<MaybeUninit<T>>::write`, which got split into
`feature(box_uninit_write)` [3].
To avoid relying on a new unstable feature, rewrite the `write` +
`assume_init` pair manually.
Link: https://github.com/rust-lang/rust/issues/63291 [1]
Link: https://github.com/rust-lang/rust/pull/129401 [2]
Link: https://github.com/rust-lang/rust/issues/129397 [3]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Matt Gilbride <mattgilbride@google.com>
Link: https://lore.kernel.org/r/20240904144229.18592-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
rust/kernel/alloc/box_ext.rs | 6 ++++--
rust/kernel/rbtree.rs | 17 ++++++++---------
2 files changed, 12 insertions(+), 11 deletions(-)
diff --git a/rust/kernel/alloc/box_ext.rs b/rust/kernel/alloc/box_ext.rs
index b68ade26a42dd..5b1550d620fd5 100644
--- a/rust/kernel/alloc/box_ext.rs
+++ b/rust/kernel/alloc/box_ext.rs
@@ -26,9 +26,11 @@ pub trait BoxExt<T>: Sized {
/// use kernel::alloc::{flags, box_ext::BoxExt};
/// let value = Box::new([0; 32], flags::GFP_KERNEL)?;
/// assert_eq!(*value, [0; 32]);
- /// let value = Box::drop_contents(value);
+ /// let mut value = Box::drop_contents(value);
/// // Now we can re-use `value`:
- /// let value = Box::write(value, [1; 32]);
+ /// value.write([1; 32]);
+ /// // SAFETY: We just wrote to it.
+ /// let value = unsafe { value.assume_init() };
/// assert_eq!(*value, [1; 32]);
/// # Ok::<(), Error>(())
/// ```
diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs
index 48ceb9560bf53..25eb36fd1cdce 100644
--- a/rust/kernel/rbtree.rs
+++ b/rust/kernel/rbtree.rs
@@ -1059,15 +1059,14 @@ impl<K, V> RBTreeNodeReservation<K, V> {
/// Initialises a node reservation.
///
/// It then becomes an [`RBTreeNode`] that can be inserted into a tree.
- pub fn into_node(self, key: K, value: V) -> RBTreeNode<K, V> {
- let node = Box::write(
- self.node,
- Node {
- key,
- value,
- links: bindings::rb_node::default(),
- },
- );
+ pub fn into_node(mut self, key: K, value: V) -> RBTreeNode<K, V> {
+ self.node.write(Node {
+ key,
+ value,
+ links: bindings::rb_node::default(),
+ });
+ // SAFETY: We just wrote to it.
+ let node = unsafe { self.node.assume_init() };
RBTreeNode { node }
}
}
--
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