Re: [PATCH v3 13/13] rust: sync: add functions for initializing `UniqueArc<MaybeUninit<T>>`

From: Gary Guo
Date: Thu Mar 30 2023 - 07:09:19 EST


On Wed, 29 Mar 2023 22:33:53 +0000
y86-dev@xxxxxxxxxxxxxx wrote:

> From: Benno Lossin <y86-dev@xxxxxxxxxxxxxx>
>
> Add two functions `init_with` and `pin_init_with` to
> `UniqueArc<MaybeUninit<T>>` to initialize the memory of already allocated
> `UniqueArc`s. This is useful when you want to allocate memory check some
> condition inside of a context where allocation is forbidden and then
> conditionally initialize an object.
>
> Signed-off-by: Benno Lossin <y86-dev@xxxxxxxxxxxxxx>

Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>

> ---
> rust/kernel/sync/arc.rs | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 4ed6329a5e5f..64b0e9d67025 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -540,6 +540,30 @@ impl<T> UniqueArc<MaybeUninit<T>> {
> inner: unsafe { Arc::from_inner(inner.cast()) },
> }
> }
> +
> + /// Initialize `self` using the given initializer.
> + pub fn init_with<E>(mut self, init: impl Init<T, E>) -> core::result::Result<UniqueArc<T>, E> {
> + // SAFETY: The supplied pointer is valid for initialization.
> + match unsafe { init.__init(self.as_mut_ptr()) } {
> + // SAFETY: Initialization completed successfully.
> + Ok(()) => Ok(unsafe { self.assume_init() }),
> + Err(err) => Err(err),
> + }
> + }
> +
> + /// Pin-initialize `self` using the given pin-initializer.
> + pub fn pin_init_with<E>(
> + mut self,
> + init: impl PinInit<T, E>,
> + ) -> core::result::Result<Pin<UniqueArc<T>>, E> {
> + // SAFETY: The supplied pointer is valid for initialization and we will later pin the value
> + // to ensure it does not move.
> + match unsafe { init.__pinned_init(self.as_mut_ptr()) } {
> + // SAFETY: Initialization completed successfully.
> + Ok(()) => Ok(unsafe { self.assume_init() }.into()),
> + Err(err) => Err(err),
> + }
> + }
> }
>
> impl<T: ?Sized> From<UniqueArc<T>> for Pin<UniqueArc<T>> {
> --
> 2.39.2
>
>