[PATCH] rust: cpumask: Replace `MaybeUninit` with `Opaque::uninit`

[PATCH] rust: cpumask: Replace `MaybeUninit` with `Opaque::uninit`

[Ritvik Gupta]

Replace unsafe `MaybeUninit::uninit().assume_init()`
initialization with `Opaque::uninit()`, which is an
abstraction for handling opaque FFI types.

Suggested-by: Benno Lossin <benno.lossin@proton.me>
Link: https://github.com/Rust-for-Linux/linux/issues/1178
Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>
---
 rust/kernel/cpumask.rs | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
index 4bce230a73b68..5f84b8797c2a7 100644
--- a/rust/kernel/cpumask.rs
+++ b/rust/kernel/cpumask.rs
@@ -14,9 +14,6 @@
 #[cfg(CONFIG_CPUMASK_OFFSTACK)]
 use core::ptr::{self, NonNull};
 
-#[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
-use core::mem::MaybeUninit;
-
 use core::ops::{Deref, DerefMut};
 
 /// A CPU Mask.
@@ -266,10 +263,7 @@ pub unsafe fn new(_flags: Flags) -> Result<Self, AllocError> {
                 NonNull::new(ptr.cast()).ok_or(AllocError)?
             },
             #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
-            // SAFETY: Guaranteed by the safety requirements of the function.
-            //
-            // INVARIANT: The associated memory is freed when the `CpumaskVar` goes out of scope.
-            mask: unsafe { MaybeUninit::uninit().assume_init() },
+            mask: Cpumask(Opaque::uninit()),
         })
     }
 

base-commit: 2009a2d5696944d85c34d75e691a6f3884e787c0
-- 
2.50.0

Re: [PATCH] rust: cpumask: Replace `MaybeUninit` with `Opaque::uninit`

[Alice Ryhl]

On Thu, Jul 10, 2025 at 2:37 PM Ritvik Gupta <ritvikfoss@gmail.com> wrote:
>
> Replace unsafe `MaybeUninit::uninit().assume_init()`
> initialization with `Opaque::uninit()`, which is an
> abstraction for handling opaque FFI types.
>
> Suggested-by: Benno Lossin <benno.lossin@proton.me>
> Link: https://github.com/Rust-for-Linux/linux/issues/1178
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>

I would make the same change to the mem::zeroed() call in
CpumaskVar::new_zeroed().

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH] rust: cpumask: Replace `MaybeUninit` with `Opaque::uninit`

[Benno Lossin]

On Thu Jul 10, 2025 at 2:38 PM CEST, Ritvik Gupta wrote:
> Replace unsafe `MaybeUninit::uninit().assume_init()`
> initialization with `Opaque::uninit()`, which is an
> abstraction for handling opaque FFI types.
>
> Suggested-by: Benno Lossin <benno.lossin@proton.me>

@Viresh when you take this, please use <lossin@kernel.org> :)

(it also is in .mailmap, so maybe it will automatically be fixed?)

> Link: https://github.com/Rust-for-Linux/linux/issues/1178
> Signed-off-by: Ritvik Gupta <ritvikfoss@gmail.com>

Thanks!

Reviewed-by: Benno Lossin <lossin@kernel.org>

---
Cheers,
Benno

> ---
>  rust/kernel/cpumask.rs | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)