Re: [PATCH v5 04/17] rust: task: remove use of `addr_of!` macro

Re: [PATCH v5 04/17] rust: task: remove use of `addr_of!` macro

[Benno Lossin]

On Thu Mar 20, 2025 at 3:07 AM CET, Antonio Hickey wrote:
> The use of `addr_of!` here is unnecessary since its immediately
> dereferenced. The main benefit of `addr_of!` is to avoid intermediate
> field loads without immediate dereferencing, so there's no benefit in
> using it here.
>
> We can achieve the same behavior by directly accessing the
> `group_leader` and `pid` fields, which is more idiomatic.
>
> 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>

Reviewed-by: Benno Lossin <benno.lossin@proton.me>

---
Cheers,
Benno

> ---
>  rust/kernel/task.rs | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

[PATCH v5 04/17] rust: task: remove use of `addr_of!` macro

[Antonio Hickey]

The use of `addr_of!` here is unnecessary since its immediately
dereferenced. The main benefit of `addr_of!` is to avoid intermediate
field loads without immediate dereferencing, so there's no benefit in
using it here.

We can achieve the same behavior by directly accessing the
`group_leader` and `pid` fields, which is more idiomatic.

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/task.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 49012e711942..568b528e2cc4 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -257,7 +257,7 @@ pub fn as_ptr(&self) -> *mut bindings::task_struct {
     pub fn group_leader(&self) -> &Task {
         // SAFETY: The group leader of a task never changes after initialization, so reading this
         // field is not a data race.
-        let ptr = unsafe { *ptr::addr_of!((*self.as_ptr()).group_leader) };
+        let ptr = unsafe { (*self.as_ptr()).group_leader };
 
         // SAFETY: The lifetime of the returned task reference is tied to the lifetime of `self`,
         // and given that a task has a reference to its group leader, we know it must be valid for
@@ -269,7 +269,7 @@ pub fn group_leader(&self) -> &Task {
     pub fn pid(&self) -> Pid {
         // SAFETY: The pid of a task never changes after initialization, so reading this field is
         // not a data race.
-        unsafe { *ptr::addr_of!((*self.as_ptr()).pid) }
+        unsafe { (*self.as_ptr()).pid }
     }
 
     /// Returns the UID of the given task.

Re: [PATCH v5 04/17] rust: task: remove use of `addr_of!` macro

[Miguel Ojeda]

On Thu, Mar 20, 2025 at 3:08 AM Antonio Hickey
<contact@antoniohickey.com> wrote:
>
> Suggested-by: Benno Lossin <benno.lossin@proton.me>
> Link: https://github.com/Rust-for-Linux/linux/issues/1148

I think I would drop these two lines -- Benno definitely suggested
what triggered this series, but I think the Link does not apply to
this particular patch, and Boqun suggested this particular change in a
review anyway.

Cheers,
Miguel