On Fri Mar 7, 2025 at 10:58 PM CET, 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@xxxxxxxxxx/ [1] > Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxx> > --- > rust/kernel/workqueue.rs | 45 ++++++++++++--------------------------------- > 1 file changed, 12 insertions(+), 33 deletions(-) What is the motivation of this change? I didn't follow the discussion, so if you explained it there, it would be nice if you could also add it to this commit message. > diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs > index 0cd100d2aefb..0e2e0ecc58a6 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. > /// > /// [`impl_has_work!`]: crate::impl_has_work > -/// [`OFFSET`]: HasWork::OFFSET > pub unsafe trait HasWork<T, const ID: u64 = 0> { > - /// The offset of the [`Work<T, ID>`] field. > - const OFFSET: usize; > - > - /// Returns the offset of the [`Work<T, ID>`] field. > - /// > - /// This method exists because the [`OFFSET`] constant cannot be accessed if the type is not > - /// [`Sized`]. > - /// > - /// [`OFFSET`]: HasWork::OFFSET > - #[inline] > - fn get_work_offset(&self) -> usize { > - Self::OFFSET > - } > - > /// Returns a pointer to the [`Work<T, ID>`] field. > /// > /// # Safety > /// > /// The provided pointer must point at a valid struct of type `Self`. > - #[inline] > - unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID> { > - // SAFETY: The caller promises that the pointer is valid. > - unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut Work<T, ID> } > - } > + unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID>; > > /// Returns a pointer to the struct containing the [`Work<T, ID>`] field. > /// > /// # Safety > /// > /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`. > - #[inline] > - unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self > - where > - Self: Sized, This bound is required in order to allow the usage of `dyn HasWork` (ie object safety), so it should stay. Maybe add a comment explaining why it's there. --- Cheers, Benno > - { > - // SAFETY: The caller promises that the pointer points at a field of the right type in the > - // right kind of struct. > - unsafe { (ptr as *mut u8).sub(Self::OFFSET) as *mut Self } > - } > + unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self; > } > > /// Used to safely implement the [`HasWork<T, ID>`] trait. > @@ -504,8 +476,6 @@ macro_rules! impl_has_work { > // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right > // type. > unsafe impl$(<$($generics)+>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self { > - const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize; > - > #[inline] > 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. > @@ -513,6 +483,15 @@ unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_typ > ::core::ptr::addr_of_mut!((*ptr).$field) > } > } > + > + #[inline] > + unsafe fn work_container_of( > + ptr: *mut $crate::workqueue::Work<$work_type $(, $id)?>, > + ) -> *mut Self { > + // SAFETY: The caller promises that the pointer points at a field of the right type > + // in the right kind of struct. > + unsafe { $crate::container_of!(ptr, Self, $field) } > + } > } > )*}; > }
