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rust: avoid box_uninit_write feature

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Like commit 0903b9e2a4 ("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>
This commit is contained in:
Miguel Ojeda 2024-09-04 16:42:29 +02:00
parent 68d3b6aa08
commit ab309b6e08
2 changed files with 12 additions and 11 deletions
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6
rust/kernel/alloc/box_ext.rs
View File

@ -26,9 +26,11 @@ pub trait BoxExt<T>: Sized {
/// use kernel::alloc::{flags, box_ext::BoxExt}; /// use kernel::alloc::{flags, box_ext::BoxExt};
/// let value = Box::new([0; 32], flags::GFP_KERNEL)?; /// let value = Box::new([0; 32], flags::GFP_KERNEL)?;
/// assert_eq!(*value, [0; 32]); /// assert_eq!(*value, [0; 32]);
/// let value = Box::drop_contents(value); /// let mut value = Box::drop_contents(value);
/// // Now we can re-use `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]); /// assert_eq!(*value, [1; 32]);
/// # Ok::<(), Error>(()) /// # Ok::<(), Error>(())
/// ``` /// ```

17
rust/kernel/rbtree.rs
View File

@ -1059,15 +1059,14 @@ impl<K, V> RBTreeNodeReservation<K, V> {
/// Initialises a node reservation. /// Initialises a node reservation.
/// ///
/// It then becomes an [`RBTreeNode`] that can be inserted into a tree. /// It then becomes an [`RBTreeNode`] that can be inserted into a tree.
pub fn into_node(self, key: K, value: V) -> RBTreeNode<K, V> { pub fn into_node(mut self, key: K, value: V) -> RBTreeNode<K, V> {
let node = Box::write( self.node.write(Node {
self.node, key,
Node { value,
key, links: bindings::rb_node::default(),
value, });
links: bindings::rb_node::default(), // SAFETY: We just wrote to it.
}, let node = unsafe { self.node.assume_init() };
);
RBTreeNode { node } RBTreeNode { node }
} }
} }