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 00/17] refactor to utilize `&raw [const|mut]`

[Antonio Hickey]

This patch set enables the `raw_ref_op` feature, which became stable 
in Rust 1.82.

It then replaces all occurences of `addr_of!(place)` and
`addr_of_mut!(place)` with `&raw const place` and `&raw mut place`.

Finally it adds the previous macros `addr_of!` and `addr_of_mut!` to
the disallowed macros in `.clippy.toml`.

Changes in v5:
- Fix doctest errors when compiling on the minimum Rust version (1.78)
  due to not having the `raw_ref_op` feature enabled for doctests.
- Reword commit messages to more accurately describe the changes.
- Replace unsafe call to `Opaque::raw_get` with pointer casting
  in workqueue.
- Fix clippy disallowed macros message for `core::ptr::addr_of`
- Link to v4: https://lore.kernel.org/all/20250316061429.817126-1-contact@antoniohickey.com/

Changes in v4:
- Fix comment typo.
- Fix clippy issues.
- Add more context and link for disallowed macros with clippy.
- Separate the patch replacing of `addr_of[_mut]!` macros with
  `&raw [const|mut]` into smaller patches for each section.
  (PATCH v3 2/3 -> PATCH v4 2/16 through 15/16)
- Fix email typo.
- Link to v3: https://lore.kernel.org/all/0100019597091f92-cb55b6cd-4d06-4d14-8d9c-1a1314949a00-000000@email.amazonses.com/

Changes in v3:
- Re ordered the patches, so that the patch adding the `addr_of[_mut]!`
  macros to the disallowed macros in clippy is applied after replacing
  all the instances of `addr_of_[_mut]` with `&raw [const|mut]`.
  (moved PATCH v2 2/3 -> PATCH v3 3/3 and PATCH v2 3/3 -> PATCH v3 2/3)
- Link to v2: https://lore.kernel.org/all/0100019592c224ba-0cf38e16-2aa2-459d-99cd-09a463d616d4-000000@email.amazonses.com/

Changes in v2:   
- Fix `&raw place` should be `&raw const place`
- Fix email typo
- Link to v1: https://lore.kernel.org/all/010001958dfeacb5-9039aaab-6114-494a-9f1d-f13982091169-000000@email.amazonses.com/

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>



Antonio Hickey (17):
  rust: enable `raw_ref_op` feature
  rust: init: refactor to use `&raw [const|mut]`
  rust: list: refactor to use `&raw [const|mut]`
  rust: task: remove use of `addr_of!` macro
  rust: faux: refactor to use `&raw [const|mut]`
  rust: platform: refactor to use `&raw [const|mut]`
  rust: pci: refactor to use `&raw [const|mut]`
  rust: kunit: refactor to use `&raw [const|mut]`
  rust: workqueue: refactor to use `&raw [const|mut]`
  rust: workqueue: replace `raw_get` with pointer cast
  rust: rbtree: refactor to use `&raw [const|mut]`
  rust: net: phy: refactor to use `&raw [const|mut]`
  rust: sync: arc: refactor to use `&raw [const|mut]`
  rust: jump_label: refactor to use `&raw [const|mut]`
  rust: fs: file: refactor to use `&raw [const|mut]`
  rust: block: refactor to use `&raw [const|mut]`
  rust: clippy: disallow `addr_of[_mut]!` macros

 .clippy.toml                           |  4 ++++
 rust/kernel/block/mq/request.rs        |  4 ++--
 rust/kernel/faux.rs                    |  4 ++--
 rust/kernel/fs/file.rs                 |  2 +-
 rust/kernel/init.rs                    |  8 ++++----
 rust/kernel/init/macros.rs             | 28 +++++++++++++-------------
 rust/kernel/jump_label.rs              |  4 ++--
 rust/kernel/kunit.rs                   |  4 ++--
 rust/kernel/lib.rs                     |  2 ++
 rust/kernel/list.rs                    |  2 +-
 rust/kernel/list/impl_list_item_mod.rs |  6 +++---
 rust/kernel/net/phy.rs                 |  4 ++--
 rust/kernel/pci.rs                     |  4 ++--
 rust/kernel/platform.rs                |  4 +---
 rust/kernel/rbtree.rs                  | 22 ++++++++++----------
 rust/kernel/sync/arc.rs                |  2 +-
 rust/kernel/task.rs                    |  4 ++--
 rust/kernel/workqueue.rs               |  9 +++------
 scripts/Makefile.build                 |  4 ++--
 19 files changed, 61 insertions(+), 60 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