Re: [PATCH v4 09/16] rust: workqueue: refactor to use `&raw [const|mut]`

[Boqun Feng <boqun.feng@gmail.com>]

On Sun, Mar 16, 2025 at 02:14:18AM -0400, Antonio Hickey wrote:
> Replacing all occurrences of `addr_of!(place)` and `addr_of_mut!(place)`
> with `&raw const place` and `&raw mut place` respectively.
> 
> This will allow us to reduce macro complexity, and improve consistency
> with existing reference syntax as `&raw const`, `&raw mut` are similar
> to `&`, `&mut` making it fit more naturally with other existing code.
> 
> Suggested-by: Benno Lossin <benno.lossin@proton.me>
> Link: https://github.com/Rust-for-Linux/linux/issues/1148
> Signed-off-by: Antonio Hickey <contact@antoniohickey.com>
> ---
>  rust/kernel/workqueue.rs | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> index 0cd100d2aefb..4e27df324d26 100644
> --- a/rust/kernel/workqueue.rs
> +++ b/rust/kernel/workqueue.rs
> @@ -401,9 +401,10 @@ pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self
>      pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
>          // SAFETY: The caller promises that the pointer is aligned and not dangling.
>          //
> -        // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that
> -        // the compiler does not complain that the `work` field is unused.
> -        unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).work)) }
> +        // A pointer cast would also be ok due to `#[repr(transparent)]`. We use
> +        // `&raw const (*ptr).work` so that the compiler does not complain that the
> +        // `work` field is unused.

I think we can actually use the pointer casting here. Because now we use
pin-init for Work initialization, so `work` field is always used.

Could you replace this with a:

	// CAST: `Work` is transparent to `bindings::work_struct`.
	ptr.cast_mut().cast()

in a separate patch?

Thanks!

Regards,
Boqun

> +        unsafe { Opaque::raw_get(&raw const (*ptr).work) }
>      }
>  }
>  
> @@ -510,7 +511,7 @@ macro_rules! impl_has_work {
>              unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
>                  // SAFETY: The caller promises that the pointer is not dangling.
>                  unsafe {
> -                    ::core::ptr::addr_of_mut!((*ptr).$field)
> +                    &raw mut (*ptr).$field
>                  }
>              }
>          }
> -- 
> 2.48.1
>