Re: [PATCH v2 2/2] rust: workqueue: remove HasWork::OFFSET

[Alice Ryhl <aliceryhl@google.com>]

On Thu, Apr 10, 2025 at 10:15:53AM -0400, Tamir Duberstein wrote:
> On Thu, Apr 10, 2025 at 5:16 AM Alice Ryhl <aliceryhl@google.com> wrote:
> >
> > On Wed, Apr 09, 2025 at 06:03:22AM -0400, Tamir Duberstein wrote:
> > > Implement `HasWork::work_container_of` in `impl_has_work!`, narrowing
> > > the interface of `HasWork` and replacing pointer arithmetic with
> > > `container_of!`. Remove the provided implementation of
> > > `HasWork::get_work_offset` without replacement; an implementation is
> > > already generated in `impl_has_work!`. Remove the `Self: Sized` bound on
> > > `HasWork::work_container_of` which was apparently necessary to access
> > > `OFFSET` as `OFFSET` no longer exists.
> > >
> > > A similar API change was discussed on the hrtimer series[1].
> > >
> > > Link: https://lore.kernel.org/all/20250224-hrtimer-v3-v6-12-rc2-v9-1-5bd3bf0ce6cc@kernel.org/ [1]
> > > Reviewed-by: Benno Lossin <benno.lossin@proton.me>
> > > Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> > > Tested-by: Alice Ryhl <aliceryhl@google.com>
> > > Signed-off-by: Tamir Duberstein <tamird@gmail.com>
> > > ---
> > >  rust/kernel/workqueue.rs | 45 ++++++++++++---------------------------------
> > >  1 file changed, 12 insertions(+), 33 deletions(-)
> > >
> > > diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
> > > index f98bd02b838f..1d640dbdc6ad 100644
> > > --- a/rust/kernel/workqueue.rs
> > > +++ b/rust/kernel/workqueue.rs
> > > @@ -429,51 +429,23 @@ pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
> > >  ///
> > >  /// # Safety
> > >  ///
> > > -/// The [`OFFSET`] constant must be the offset of a field in `Self` of type [`Work<T, ID>`]. The
> > > -/// methods on this trait must have exactly the behavior that the definitions given below have.
> > > +/// The methods on this trait must have exactly the behavior that the definitions given below have.
> >
> > This wording probably needs to be rephrased. You got rid of the
> > definitions that sentence refers to.
> 
> I don't follow. What definitions was it referring to? I interpreted it
> as having referred to all the items: constants *and* methods.

I meant for it to refer to the default implementations of the methods.

> Could you propose an alternate phrasing?

I guess the requirements are something along the lines of raw_get_work
must return a value pointer, and it must roundtrip with
raw_container_of.

Alice