On Sat, 29 Jul 2023 09:10:22 +0000
Benno Lossin <benno.lossin@proton.me> wrote:
> Remove the blanket implementation of `PinInit<T, E> for I where I:
> Init<T, E>`. This blanket implementation prevented custom types that
> implement `PinInit`.
>
> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> v2 -> v3:
> - add blank missing line,
> - added Reviewed-by's from Martin and Alice.
>
> rust/kernel/init.rs | 21 ++++++++-------------
> rust/kernel/init/__internal.rs | 12 ++++++++++++
> 2 files changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
> index 06ecab4901f2..040dc9a5f9fd 100644
> --- a/rust/kernel/init.rs
> +++ b/rust/kernel/init.rs
> @@ -807,7 +807,7 @@ pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
> ///
> /// [`Arc<T>`]: crate::sync::Arc
> #[must_use = "An initializer must be used in order to create its value."]
> -pub unsafe trait Init<T: ?Sized, E = Infallible>: Sized {
> +pub unsafe trait Init<T: ?Sized, E = Infallible>: PinInit<T, E> {
> /// Initializes `slot`.
> ///
> /// # Safety
> @@ -818,18 +818,6 @@ pub unsafe trait Init<T: ?Sized, E = Infallible>: Sized {
> unsafe fn __init(self, slot: *mut T) -> Result<(), E>;
> }
>
> -// SAFETY: Every in-place initializer can also be used as a pin-initializer.
> -unsafe impl<T: ?Sized, E, I> PinInit<T, E> for I
> -where
> - I: Init<T, E>,
> -{
> - unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
> - // SAFETY: `__init` meets the same requirements as `__pinned_init`, except that it does not
> - // require `slot` to not move after init.
> - unsafe { self.__init(slot) }
> - }
> -}
> -
> /// Creates a new [`PinInit<T, E>`] from the given closure.
> ///
> /// # Safety
> @@ -971,6 +959,13 @@ unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
> }
> }
>
> +// SAFETY: Every type can be initialized by-value. `__pinned_init` calls `__init`.
> +unsafe impl<T, E> PinInit<T, E> for T {
> + unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
> + unsafe { self.__init(slot) }
> + }
> +}
> +
> /// Smart pointer that can initialize memory in-place.
> pub trait InPlaceInit<T>: Sized {
> /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
> diff --git a/rust/kernel/init/__internal.rs b/rust/kernel/init/__internal.rs
> index 7abd1fb65e41..12e195061525 100644
> --- a/rust/kernel/init/__internal.rs
> +++ b/rust/kernel/init/__internal.rs
> @@ -32,6 +32,18 @@ unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
> }
> }
>
> +// SAFETY: While constructing the `InitClosure`, the user promised that it upholds the
> +// `__pinned_init` invariants.
> +unsafe impl<T: ?Sized, F, E> PinInit<T, E> for InitClosure<F, T, E>
> +where
> + F: FnOnce(*mut T) -> Result<(), E>,
> +{
> + #[inline]
> + unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
> + (self.0)(slot)
> + }
> +}
> +
> /// This trait is only implemented via the `#[pin_data]` proc-macro. It is used to facilitate
> /// the pin projections within the initializers.
> ///