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Message-ID: <20230329223239.138757-7-y86-dev@protonmail.com>
Date: Wed, 29 Mar 2023 22:33:18 +0000
From: y86-dev@...tonmail.com
To: Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Alice Ryhl <alice@...l.io>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
patches@...ts.linux.dev
Subject: [PATCH v3 06/13] rust: init/sync: add `InPlaceInit` trait to pin-initialize smart pointers
From: Benno Lossin <y86-dev@...tonmail.com>
The `InPlaceInit` trait that provides two functions, for initializing
using `PinInit<T, E>` and `Init<T>`. It is implemented by `Arc<T>`,
`UniqueArc<T>` and `Box<T>`.
Signed-off-by: Benno Lossin <y86-dev@...tonmail.com>
---
rust/kernel/init.rs | 97 +++++++++++++++++++++++++++++++++++------
rust/kernel/sync/arc.rs | 25 ++++++++++-
2 files changed, 108 insertions(+), 14 deletions(-)
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 85e8d5f41b60..3d89c7e3bdb5 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -114,10 +114,13 @@
//! [`impl Init<T, E>`]: Init
//! [`Opaque`]: kernel::types::Opaque
//! [`pin_data`]: ::macros::pin_data
-//! [`UniqueArc<T>`]: kernel::sync::UniqueArc
+use crate::{
+ error::{self, Error},
+ sync::UniqueArc,
+};
use alloc::boxed::Box;
-use core::{cell::Cell, convert::Infallible, marker::PhantomData, mem::MaybeUninit, ptr};
+use core::{cell::Cell, convert::Infallible, marker::PhantomData, mem::MaybeUninit, pin::Pin, ptr};
#[doc(hidden)]
pub mod __internal;
@@ -309,7 +312,6 @@ pub mod macros;
///
/// [`try_pin_init!`]: kernel::try_pin_init
/// [`NonNull<Self>`]: core::ptr::NonNull
-/// [`Error`]: kernel::error::Error
// For a detailed example of how this macro works, see the module documentation of the hidden
// module `__internal` inside of `init/__internal.rs`.
#[macro_export]
@@ -366,8 +368,6 @@ macro_rules! pin_init {
/// }
/// }
/// ```
-///
-/// [`Error`]: kernel::error::Error
// For a detailed example of how this macro works, see the module documentation of the hidden
// module `__internal` inside of `init/__internal.rs`.
#[macro_export]
@@ -589,8 +589,6 @@ macro_rules! try_pin_init {
///
/// This initializer is for initializing data in-place that might later be moved. If you want to
/// pin-initialize, use [`pin_init!`].
-///
-/// [`Error`]: kernel::error::Error
// For a detailed example of how this macro works, see the module documentation of the hidden
// module `__internal` inside of `init/__internal.rs`.
#[macro_export]
@@ -641,8 +639,6 @@ macro_rules! init {
/// }
/// }
/// ```
-///
-/// [`Error`]: kernel::error::Error
// For a detailed example of how this macro works, see the module documentation of the hidden
// module `__internal` inside of `init/__internal.rs`.
#[macro_export]
@@ -848,7 +844,8 @@ macro_rules! try_init {
/// A pinned initializer for `T`.
///
/// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
-/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`].
+/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`]. Use the [`InPlaceInit::pin_init`] function of a
+/// smart pointer like [`Arc<T>`] on this.
///
/// Also see the [module description](self).
///
@@ -867,7 +864,6 @@ macro_rules! try_init {
///
/// [`Arc<T>`]: crate::sync::Arc
/// [`Arc::pin_init`]: crate::sync::Arc::pin_init
-/// [`UniqueArc<T>`]: kernel::sync::UniqueArc
#[must_use = "An initializer must be used in order to create its value."]
pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
/// Initializes `slot`.
@@ -884,7 +880,8 @@ pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
/// An initializer for `T`.
///
/// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
-/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`]. Because [`PinInit<T, E>`] is a super trait, you can
+/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`]. Use the [`InPlaceInit::init`] function of a smart
+/// pointer like [`Arc<T>`] on this. Because [`PinInit<T, E>`] is a super trait, you can
/// use every function that takes it as well.
///
/// Also see the [module description](self).
@@ -909,7 +906,6 @@ pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
/// move the pointee after initialization.
///
/// [`Arc<T>`]: crate::sync::Arc
-/// [`UniqueArc<T>`]: kernel::sync::UniqueArc
#[must_use = "An initializer must be used in order to create its value."]
pub unsafe trait Init<T: ?Sized, E = Infallible>: PinInit<T, E> {
/// Initializes `slot`.
@@ -1014,3 +1010,78 @@ unsafe impl<T> Init<T> for T {
Ok(())
}
}
+
+/// Smart pointer that can initialize memory in-place.
+pub trait InPlaceInit<T>: Sized {
+ /// Use the given initializer to in-place initialize a `T`.
+ ///
+ /// If `T: !Unpin` it will not be able to move afterwards.
+ fn pin_init<E>(init: impl PinInit<T, E>) -> error::Result<Pin<Self>>
+ where
+ Error: From<E>;
+
+ /// Use the given initializer to in-place initialize a `T`.
+ fn init<E>(init: impl Init<T, E>) -> error::Result<Self>
+ where
+ Error: From<E>;
+}
+
+impl<T> InPlaceInit<T> for Box<T> {
+ #[inline]
+ fn pin_init<E>(init: impl PinInit<T, E>) -> error::Result<Pin<Self>>
+ where
+ Error: From<E>,
+ {
+ let mut this = Box::try_new_uninit()?;
+ let slot = this.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid and will not be moved because of the `Pin::new_unchecked`
+ unsafe { init.__pinned_init(slot)? };
+ // SAFETY: All fields have been initialized.
+ Ok(unsafe { Pin::new_unchecked(this.assume_init()) })
+ }
+
+ #[inline]
+ fn init<E>(init: impl Init<T, E>) -> error::Result<Self>
+ where
+ Error: From<E>,
+ {
+ let mut this = Box::try_new_uninit()?;
+ let slot = this.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid
+ unsafe { init.__init(slot)? };
+ // SAFETY: All fields have been initialized.
+ Ok(unsafe { this.assume_init() })
+ }
+}
+
+impl<T> InPlaceInit<T> for UniqueArc<T> {
+ #[inline]
+ fn pin_init<E>(init: impl PinInit<T, E>) -> error::Result<Pin<Self>>
+ where
+ Error: From<E>,
+ {
+ let mut this = UniqueArc::try_new_uninit()?;
+ let slot = this.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid and will not be moved because of the `Pin::new_unchecked`.
+ unsafe { init.__pinned_init(slot)? };
+ // SAFETY: All fields have been initialized.
+ Ok(unsafe { Pin::new_unchecked(this.assume_init()) })
+ }
+
+ #[inline]
+ fn init<E>(init: impl Init<T, E>) -> error::Result<Self>
+ where
+ Error: From<E>,
+ {
+ let mut this = UniqueArc::try_new_uninit()?;
+ let slot = this.as_mut_ptr();
+ // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+ // slot is valid.
+ unsafe { init.__init(slot)? };
+ // SAFETY: All fields have been initialized.
+ Ok(unsafe { this.assume_init() })
+ }
+}
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 16ec174637b2..77a3833cc265 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -17,7 +17,8 @@
use crate::{
bindings,
- error::Result,
+ error::{Error, Result},
+ init::{InPlaceInit, Init, PinInit},
types::{ForeignOwnable, Opaque},
};
use alloc::boxed::Box;
@@ -163,6 +164,28 @@ impl<T> Arc<T> {
// `Arc` object.
Ok(unsafe { Self::from_inner(Box::leak(inner).into()) })
}
+
+ /// Use the given initializer to in-place initialize a `T`.
+ ///
+ /// If `T: !Unpin` it will not be able to move afterwards.
+ #[inline]
+ pub fn pin_init<E>(init: impl PinInit<T, E>) -> Result<Self>
+ where
+ Error: From<E>,
+ {
+ UniqueArc::pin_init(init).map(|u| u.into())
+ }
+
+ /// Use the given initializer to in-place initialize a `T`.
+ ///
+ /// This is equivalent to [`pin_init`], since an [`Arc`] is always pinned.
+ #[inline]
+ pub fn init<E>(init: impl Init<T, E>) -> Result<Self>
+ where
+ Error: From<E>,
+ {
+ UniqueArc::init(init).map(|u| u.into())
+ }
}
impl<T: ?Sized> Arc<T> {
--
2.39.2
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