* [PATCH v18 1/8] rust: alloc: add `KBox::into_non_null`
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 2/8] rust: types: Add Ownable/Owned types Andreas Hindborg
` (6 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm
Add a method to consume a `Box<T, A>` and return a `NonNull<T>`. This
is a convenience wrapper around `Self::into_raw` for callers that need
a `NonNull` pointer rather than a raw pointer.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
---
rust/kernel/alloc/kbox.rs | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
index 35d1e015848dd..d534e8adcf7b3 100644
--- a/rust/kernel/alloc/kbox.rs
+++ b/rust/kernel/alloc/kbox.rs
@@ -211,6 +211,15 @@ pub fn leak<'a>(b: Self) -> &'a mut T {
// which points to an initialized instance of `T`.
unsafe { &mut *Box::into_raw(b) }
}
+
+ /// Consumes the `Box<T,A>` and returns a `NonNull<T>`.
+ ///
+ /// Like [`Self::into_raw`], but returns a `NonNull`.
+ #[inline]
+ pub fn into_non_null(b: Self) -> NonNull<T> {
+ // SAFETY: `KBox::into_raw` returns a valid pointer.
+ unsafe { NonNull::new_unchecked(Self::into_raw(b)) }
+ }
}
impl<T, A> Box<MaybeUninit<T>, A>
--
2.51.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v18 2/8] rust: types: Add Ownable/Owned types
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 1/8] rust: alloc: add `KBox::into_non_null` Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
[not found] ` <RGwPXnEIbmBiUBfnS6xf4w_nFgCkKyGqve0WSY_SbSrRXPnRF3zE_LoMjmCUpsnUBAZU8NQz5SkXWgUU7xZnBA==@protonmail.internalid>
2026-06-25 10:15 ` [PATCH v18 3/8] rust: implement `ForeignOwnable` for `Owned` Andreas Hindborg
` (5 subsequent siblings)
7 siblings, 1 reply; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Asahi Lina, Oliver Mangold, Boqun Feng
From: Asahi Lina <lina+kernel@asahilina.net>
By analogy to `AlwaysRefCounted` and `ARef`, an `Ownable` type is a
(typically C FFI) type that *may* be owned by Rust, but need not be. Unlike
`AlwaysRefCounted`, this mechanism expects the reference to be unique
within Rust, and does not allow cloning.
Conceptually, this is similar to a `KBox<T>`, except that it delegates
resource management to the `T` instead of using a generic allocator.
[ om:
- Split code into separate file and `pub use` it from types.rs.
- Make from_raw() and into_raw() public.
- Remove OwnableMut, and make DerefMut dependent on Unpin instead.
- Usage example/doctest for Ownable/Owned.
- Fixes to documentation and commit message.
]
Link: https://lore.kernel.org/all/20250202-rust-page-v1-1-e3170d7fe55e@asahilina.net/
Signed-off-by: Asahi Lina <lina+kernel@asahilina.net>
Co-developed-by: Oliver Mangold <oliver.mangold@pm.me>
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
[ Andreas: Updated documentation, examples, and formatting. Change safety
requirements, safety comments. ]
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/lib.rs | 1 +
rust/kernel/owned.rs | 188 +++++++++++++++++++++++++++++++++++++++++++++++
rust/kernel/sync/aref.rs | 5 ++
rust/kernel/types.rs | 5 ++
4 files changed, 199 insertions(+)
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 9512af7156df2..eb5256204a174 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -101,6 +101,7 @@
pub mod of;
#[cfg(CONFIG_PM_OPP)]
pub mod opp;
+pub mod owned;
pub mod page;
#[cfg(CONFIG_PCI)]
pub mod pci;
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
new file mode 100644
index 0000000000000..7fe9ec3e55126
--- /dev/null
+++ b/rust/kernel/owned.rs
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Unique owned pointer types for objects with custom drop logic.
+//!
+//! These pointer types are useful for C-allocated objects which by API-contract
+//! are owned by Rust, but need to be freed through the C API.
+
+use core::{
+ mem::ManuallyDrop,
+ ops::{
+ Deref,
+ DerefMut, //
+ },
+ pin::Pin,
+ ptr::NonNull, //
+};
+
+/// Types that specify their own way of performing allocation and destruction. Typically, this trait
+/// is implemented on types from the C side.
+///
+/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type. This
+/// is useful when it is desirable to tie the lifetime of the reference to an owned object, rather
+/// than pass around a bare reference. [`Ownable`] types can define custom drop logic that is
+/// executed when the owned reference [`Owned<Self>`] pointing to the object is dropped.
+///
+/// Note: The underlying object is not required to provide internal reference counting, because it
+/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
+/// [`AlwaysRefCounted`](crate::sync::aref::AlwaysRefCounted) should be implemented.
+///
+/// # Examples
+///
+/// A minimal example implementation of [`Ownable`] and its usage with [`Owned`] looks like
+/// this:
+///
+/// ```
+/// # #![expect(clippy::disallowed_names)]
+/// # use core::cell::Cell;
+/// # use core::ptr::NonNull;
+/// # use kernel::sync::global_lock;
+/// # use kernel::alloc::{flags, kbox::KBox, AllocError};
+/// # use kernel::types::{Owned, Ownable};
+///
+/// // Let's count the allocations to see if freeing works.
+/// kernel::sync::global_lock! {
+/// // SAFETY: we call `init()` right below, before doing anything else.
+/// unsafe(uninit) static FOO_ALLOC_COUNT: Mutex<usize> = 0;
+/// }
+/// // SAFETY: We call `init()` only once, here.
+/// unsafe { FOO_ALLOC_COUNT.init() };
+///
+/// struct Foo;
+///
+/// impl Foo {
+/// fn new() -> Result<Owned<Self>> {
+/// // We are just using a `KBox` here to handle the actual allocation, as our `Foo` is
+/// // not actually a C-allocated object.
+/// let result = KBox::new(
+/// Foo {},
+/// flags::GFP_KERNEL,
+/// )?;
+/// let result = KBox::into_non_null(result);
+/// // Count new allocation
+/// *FOO_ALLOC_COUNT.lock() += 1;
+/// // SAFETY:
+/// // - We just allocated the `Self`, thus it is valid and we own it.
+/// // - We can transfer this ownership to the `from_raw` method.
+/// Ok(unsafe { Owned::from_raw(result) })
+/// }
+/// }
+///
+/// impl Ownable for Foo {
+/// unsafe fn release(this: NonNull<Self>) {
+/// // SAFETY: The [`KBox<Self>`] is still alive. We can pass ownership to the [`KBox`], as
+/// // by requirement on calling this function.
+/// drop(unsafe { KBox::from_raw(this.as_ptr()) });
+/// // Count released allocation
+/// *FOO_ALLOC_COUNT.lock() -= 1;
+/// }
+/// }
+///
+/// {
+/// let foo = Foo::new()?;
+/// assert!(*FOO_ALLOC_COUNT.lock() == 1);
+/// }
+/// // `foo` is out of scope now, so we expect no live allocations.
+/// assert!(*FOO_ALLOC_COUNT.lock() == 0);
+/// # Ok::<(), Error>(())
+/// ```
+pub trait Ownable {
+ /// Tear down this `Ownable`.
+ ///
+ /// Implementers of `Ownable` can use this function to clean up the use of `Self`. This can
+ /// include freeing the underlying object.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that they have exclusive ownership of the `Self` pointed to by `this`,
+ /// and that this ownership is transferred to the `release` method. `this` must not be used
+ /// after calling this method, as the underlying object may have been freed.
+ unsafe fn release(this: NonNull<Self>);
+}
+
+/// A mutable reference to an owned `T`.
+///
+/// The [`Ownable`] is automatically freed or released when an instance of [`Owned`] is
+/// dropped.
+///
+/// # Invariants
+///
+/// - Until `T::release` is called, this `Owned<T>` exclusively owns the underlying `T`.
+/// - The `T` value is pinned.
+pub struct Owned<T: Ownable> {
+ ptr: NonNull<T>,
+}
+
+impl<T: Ownable> Owned<T> {
+ /// Creates a new instance of [`Owned`].
+ ///
+ /// This function takes over ownership of the underlying object.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that:
+ /// - `ptr` points to a valid instance of `T`.
+ /// - Until `T::release` is called, the returned `Owned<T>` exclusively owns the underlying `T`.
+ #[inline]
+ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
+ // INVARIANT: By function safety requirement we satisfy the first invariant of `Self`.
+ // We treat `T` as pinned from now on.
+ Self { ptr }
+ }
+
+ /// Consumes the [`Owned`], returning a raw pointer.
+ ///
+ /// This function does not drop the underlying `T`. When this function returns, ownership of the
+ /// underlying `T` is with the caller.
+ #[inline]
+ pub fn into_raw(me: Self) -> NonNull<T> {
+ ManuallyDrop::new(me).ptr
+ }
+
+ /// Get a pinned mutable reference to the data owned by this `Owned<T>`.
+ #[inline]
+ pub fn as_pin_mut(&mut self) -> Pin<&mut T> {
+ // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
+ // return a mutable reference to it.
+ let unpinned = unsafe { self.ptr.as_mut() };
+
+ // SAFETY: By type invariant `T` is pinned.
+ unsafe { Pin::new_unchecked(unpinned) }
+ }
+}
+
+// SAFETY: It is safe to send an [`Owned<T>`] to another thread when the underlying `T` is [`Send`],
+// because of the ownership invariant. Sending an [`Owned<T>`] is equivalent to sending the `T`.
+unsafe impl<T: Ownable + Send> Send for Owned<T> {}
+
+// SAFETY: It is safe to send [`&Owned<T>`] to another thread when the underlying `T` is [`Sync`],
+// because of the ownership invariant. Sending an [`&Owned<T>`] is equivalent to sending the `&T`.
+unsafe impl<T: Ownable + Sync> Sync for Owned<T> {}
+
+impl<T: Ownable> Deref for Owned<T> {
+ type Target = T;
+
+ #[inline]
+ fn deref(&self) -> &Self::Target {
+ // SAFETY: The type invariants guarantee that the object is valid.
+ unsafe { self.ptr.as_ref() }
+ }
+}
+
+impl<T: Ownable + Unpin> DerefMut for Owned<T> {
+ #[inline]
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
+ // return a mutable reference to it.
+ unsafe { self.ptr.as_mut() }
+ }
+}
+
+impl<T: Ownable> Drop for Owned<T> {
+ #[inline]
+ fn drop(&mut self) {
+ // SAFETY: By existence of `&mut self` we exclusively own `self` and the underlying `T`. As
+ // we are dropping `self`, we can transfer ownership of the `T` to the `release` method.
+ unsafe { T::release(self.ptr) };
+ }
+}
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index b721b2e00b986..3bd5eb8a1a526 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -34,6 +34,11 @@
/// Rust code, the recommendation is to use [`Arc`](crate::sync::Arc) to create reference-counted
/// instances of a type.
///
+/// Note: Implementing this trait allows types to be wrapped in an [`ARef<Self>`]. It requires an
+/// internal reference count and provides only shared references. If unique references are required
+/// [`Ownable`](crate::types::Ownable) should be implemented which allows types to be wrapped in an
+/// [`Owned<Self>`](crate::types::Owned).
+///
/// # Safety
///
/// Implementers must ensure that increments to the reference count keep the object alive in memory
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index ac316fd7b538f..c41eab0ec983c 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -15,6 +15,11 @@
pub mod for_lt;
pub use for_lt::ForLt;
+pub use crate::owned::{
+ Ownable,
+ Owned, //
+};
+
/// Used to transfer ownership to and from foreign (non-Rust) languages.
///
/// Ownership is transferred from Rust to a foreign language by calling [`Self::into_foreign`] and
--
2.51.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v18 3/8] rust: implement `ForeignOwnable` for `Owned`
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 1/8] rust: alloc: add `KBox::into_non_null` Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 2/8] rust: types: Add Ownable/Owned types Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
2026-06-25 13:29 ` Gary Guo
2026-06-25 10:15 ` [PATCH v18 4/8] rust: page: convert to `Ownable` Andreas Hindborg
` (4 subsequent siblings)
7 siblings, 1 reply; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm
Implement `ForeignOwnable` for `Owned<T>`. This allows use of `Owned<T>` in
places such as the `XArray`.
Note that `T` does not need to implement `ForeignOwnable` for `Owned<T>` to
implement `ForeignOwnable`.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/owned.rs | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index 7fe9ec3e55126..9c92d4a83cc1b 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -15,6 +15,8 @@
ptr::NonNull, //
};
+use kernel::types::ForeignOwnable;
+
/// Types that specify their own way of performing allocation and destruction. Typically, this trait
/// is implemented on types from the C side.
///
@@ -186,3 +188,54 @@ fn drop(&mut self) {
unsafe { T::release(self.ptr) };
}
}
+
+// SAFETY: We derive the pointer to `T` from a valid `T`, so the returned
+// pointer satisfy alignment requirements of `T`.
+unsafe impl<T: Ownable> ForeignOwnable for Owned<T> {
+ const FOREIGN_ALIGN: usize = core::mem::align_of::<T>();
+
+ type Borrowed<'a>
+ = &'a T
+ where
+ Self: 'a;
+ type BorrowedMut<'a>
+ = Pin<&'a mut T>
+ where
+ Self: 'a;
+
+ #[inline]
+ fn into_foreign(self) -> *mut kernel::ffi::c_void {
+ let ptr = self.ptr.as_ptr().cast();
+ core::mem::forget(self);
+ ptr
+ }
+
+ #[inline]
+ unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self {
+ // INVARIANT: By the function safety contract, `ptr` was returned by `into_foreign`, which
+ // gave up exclusive ownership of a valid, pinned `T`; we retake that ownership here.
+ Self {
+ // SAFETY: By function safety contract, `ptr` came from
+ // `into_foreign` and cannot be null.
+ ptr: unsafe { NonNull::new_unchecked(ptr.cast()) },
+ }
+ }
+
+ #[inline]
+ unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowed<'a> {
+ // SAFETY: By function safety requirements, `ptr` is valid for use as a
+ // reference for `'a`.
+ unsafe { &*ptr.cast() }
+ }
+
+ #[inline]
+ unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a> {
+ // SAFETY: By function safety requirements, `ptr` is valid for use as a
+ // unique reference for `'a`.
+ let inner = unsafe { &mut *ptr.cast() };
+
+ // SAFETY: We never move out of inner, and we do not hand out mutable
+ // references when `T: !Unpin`.
+ unsafe { Pin::new_unchecked(inner) }
+ }
+}
--
2.51.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* Re: [PATCH v18 3/8] rust: implement `ForeignOwnable` for `Owned`
2026-06-25 10:15 ` [PATCH v18 3/8] rust: implement `ForeignOwnable` for `Owned` Andreas Hindborg
@ 2026-06-25 13:29 ` Gary Guo
0 siblings, 0 replies; 12+ messages in thread
From: Gary Guo @ 2026-06-25 13:29 UTC (permalink / raw)
To: Andreas Hindborg, Danilo Krummrich, Lorenzo Stoakes,
Vlastimil Babka, Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda,
Boqun Feng, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, Lyude Paul,
Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Christian Brauner, Carlos Llamas, Rafael J. Wysocki, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
David Airlie, Simona Vetter, Alexander Viro, Jan Kara,
Igor Korotin, Viresh Kumar, Nishanth Menon, Stephen Boyd,
Bjorn Helgaas, Krzysztof Wilczyński, Pavel Tikhomirov,
Michal Wilczynski
Cc: Philipp Stanner, rust-for-linux, linux-kernel, linux-mm,
driver-core, linux-block, linux-security-module, dri-devel,
linux-fsdevel, linux-pm, linux-pci, linux-pwm
On Thu Jun 25, 2026 at 11:15 AM BST, Andreas Hindborg wrote:
> Implement `ForeignOwnable` for `Owned<T>`. This allows use of `Owned<T>` in
> places such as the `XArray`.
>
> Note that `T` does not need to implement `ForeignOwnable` for `Owned<T>` to
> implement `ForeignOwnable`.
>
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
> rust/kernel/owned.rs | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 53 insertions(+)
>
> diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
> index 7fe9ec3e55126..9c92d4a83cc1b 100644
> --- a/rust/kernel/owned.rs
> +++ b/rust/kernel/owned.rs
> @@ -15,6 +15,8 @@
> ptr::NonNull, //
> };
>
> +use kernel::types::ForeignOwnable;
> +
> /// Types that specify their own way of performing allocation and destruction. Typically, this trait
> /// is implemented on types from the C side.
> ///
> @@ -186,3 +188,54 @@ fn drop(&mut self) {
> unsafe { T::release(self.ptr) };
> }
> }
> +
> +// SAFETY: We derive the pointer to `T` from a valid `T`, so the returned
> +// pointer satisfy alignment requirements of `T`.
> +unsafe impl<T: Ownable> ForeignOwnable for Owned<T> {
> + const FOREIGN_ALIGN: usize = core::mem::align_of::<T>();
> +
> + type Borrowed<'a>
> + = &'a T
> + where
> + Self: 'a;
> + type BorrowedMut<'a>
> + = Pin<&'a mut T>
> + where
> + Self: 'a;
> +
> + #[inline]
> + fn into_foreign(self) -> *mut kernel::ffi::c_void {
> + let ptr = self.ptr.as_ptr().cast();
> + core::mem::forget(self);
> + ptr
I think the pattern in `into_raw` is better:
ManuallyDrop::new(self).ptr.as_ptr().cast()
Or perhaps this can just use `Self::into_raw(self).as_ptr().cast()`.
> + }
> +
> + #[inline]
> + unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self {
> + // INVARIANT: By the function safety contract, `ptr` was returned by `into_foreign`, which
> + // gave up exclusive ownership of a valid, pinned `T`; we retake that ownership here.
> + Self {
> + // SAFETY: By function safety contract, `ptr` came from
> + // `into_foreign` and cannot be null.
> + ptr: unsafe { NonNull::new_unchecked(ptr.cast()) },
> + }
> + }
Same here, could be using `Self::from_raw`.
However, the current code looks correct to me regardless, so:
Reviewed-by: Gary Guo <gary@garyguo.net>
Best,
Gary
> +
> + #[inline]
> + unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowed<'a> {
> + // SAFETY: By function safety requirements, `ptr` is valid for use as a
> + // reference for `'a`.
> + unsafe { &*ptr.cast() }
> + }
> +
> + #[inline]
> + unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a> {
> + // SAFETY: By function safety requirements, `ptr` is valid for use as a
> + // unique reference for `'a`.
> + let inner = unsafe { &mut *ptr.cast() };
> +
> + // SAFETY: We never move out of inner, and we do not hand out mutable
> + // references when `T: !Unpin`.
> + unsafe { Pin::new_unchecked(inner) }
> + }
> +}
^ permalink raw reply [flat|nested] 12+ messages in thread
* [PATCH v18 4/8] rust: page: convert to `Ownable`
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
` (2 preceding siblings ...)
2026-06-25 10:15 ` [PATCH v18 3/8] rust: implement `ForeignOwnable` for `Owned` Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
2026-06-25 13:32 ` Gary Guo
2026-06-25 10:15 ` [PATCH v18 5/8] rust: rename `AlwaysRefCounted` to `RefCounted` Andreas Hindborg
` (3 subsequent siblings)
7 siblings, 1 reply; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Asahi Lina
From: Asahi Lina <lina@asahilina.net>
This allows Page references to be returned as borrowed references,
without necessarily owning the struct page.
Remove `BorrowedPage` and update users to use `Owned<Page>`.
Signed-off-by: Asahi Lina <lina@asahilina.net>
[ Andreas: Fix formatting and add a safety comment, update users. ]
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
drivers/android/binder/page_range.rs | 10 +--
rust/kernel/alloc/allocator.rs | 19 +++---
rust/kernel/alloc/allocator/iter.rs | 6 +-
rust/kernel/page.rs | 122 +++++++++--------------------------
4 files changed, 46 insertions(+), 111 deletions(-)
diff --git a/drivers/android/binder/page_range.rs b/drivers/android/binder/page_range.rs
index e54a90e62402a..7941eb85b4ef4 100644
--- a/drivers/android/binder/page_range.rs
+++ b/drivers/android/binder/page_range.rs
@@ -33,7 +33,7 @@
sync::{aref::ARef, Mutex, SpinLock},
task::Pid,
transmute::FromBytes,
- types::Opaque,
+ types::{Opaque, Owned},
uaccess::UserSliceReader,
};
@@ -198,7 +198,7 @@ unsafe impl Send for Inner {}
#[repr(C)]
struct PageInfo {
lru: bindings::list_head,
- page: Option<Page>,
+ page: Option<Owned<Page>>,
range: *const ShrinkablePageRange,
}
@@ -206,7 +206,7 @@ impl PageInfo {
/// # Safety
///
/// The caller ensures that writing to `me.page` is ok, and that the page is not currently set.
- unsafe fn set_page(me: *mut PageInfo, page: Page) {
+ unsafe fn set_page(me: *mut PageInfo, page: Owned<Page>) {
// SAFETY: This pointer offset is in bounds.
let ptr = unsafe { &raw mut (*me).page };
@@ -229,13 +229,13 @@ unsafe fn get_page<'a>(me: *const PageInfo) -> Option<&'a Page> {
let ptr = unsafe { &raw const (*me).page };
// SAFETY: The pointer is valid for reading.
- unsafe { (*ptr).as_ref() }
+ unsafe { (*ptr).as_deref() }
}
/// # Safety
///
/// The caller ensures that writing to `me.page` is ok for the duration of 'a.
- unsafe fn take_page(me: *mut PageInfo) -> Option<Page> {
+ unsafe fn take_page(me: *mut PageInfo) -> Option<Owned<Page>> {
// SAFETY: This pointer offset is in bounds.
let ptr = unsafe { &raw mut (*me).page };
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index cd4203f27aed0..c7b9b069cf75d 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -169,7 +169,7 @@ unsafe fn realloc(
}
impl Vmalloc {
- /// Convert a pointer to a [`Vmalloc`] allocation to a [`page::BorrowedPage`].
+ /// Convert a pointer to a [`Vmalloc`] allocation to a [`Page`](page::Page) reference.
///
/// # Examples
///
@@ -202,20 +202,17 @@ impl Vmalloc {
///
/// - `ptr` must be a valid pointer to a [`Vmalloc`] allocation.
/// - `ptr` must remain valid for the entire duration of `'a`.
- pub unsafe fn to_page<'a>(ptr: NonNull<u8>) -> page::BorrowedPage<'a> {
+ pub unsafe fn to_page<'a>(ptr: NonNull<u8>) -> &'a page::Page {
// SAFETY: `ptr` is a valid pointer to `Vmalloc` memory.
let page = unsafe { bindings::vmalloc_to_page(ptr.as_ptr().cast()) };
- // SAFETY: `vmalloc_to_page` returns a valid pointer to a `struct page` for a valid pointer
- // to `Vmalloc` memory.
- let page = unsafe { NonNull::new_unchecked(page) };
-
// SAFETY:
- // - `page` is a valid pointer to a `struct page`, given that by the safety requirements of
- // this function `ptr` is a valid pointer to a `Vmalloc` allocation.
- // - By the safety requirements of this function `ptr` is valid for the entire lifetime of
- // `'a`.
- unsafe { page::BorrowedPage::from_raw(page) }
+ // - `vmalloc_to_page` returns a valid, non-null pointer to a `struct page` for a valid
+ // pointer to `Vmalloc` memory, given that by the safety requirements of this function
+ // `ptr` is a valid pointer to a `Vmalloc` allocation.
+ // - By the safety requirements of this function `ptr`, and hence the `struct page`, is
+ // valid for the entire lifetime of `'a`.
+ unsafe { &*page.cast() }
}
}
diff --git a/rust/kernel/alloc/allocator/iter.rs b/rust/kernel/alloc/allocator/iter.rs
index 02fda3ea5cae6..8dcc16ed89893 100644
--- a/rust/kernel/alloc/allocator/iter.rs
+++ b/rust/kernel/alloc/allocator/iter.rs
@@ -9,7 +9,7 @@
ptr::NonNull, //
};
-/// An [`Iterator`] of [`page::BorrowedPage`] items owned by a [`Vmalloc`] allocation.
+/// An [`Iterator`] of [`Page`](page::Page) references owned by a [`Vmalloc`] allocation.
///
/// # Guarantees
///
@@ -28,11 +28,11 @@ pub struct VmallocPageIter<'a> {
size: usize,
/// The current page index of the [`Iterator`].
index: usize,
- _p: PhantomData<page::BorrowedPage<'a>>,
+ _p: PhantomData<&'a page::Page>,
}
impl<'a> Iterator for VmallocPageIter<'a> {
- type Item = page::BorrowedPage<'a>;
+ type Item = &'a page::Page;
fn next(&mut self) -> Option<Self::Item> {
let offset = self.index.checked_mul(page::PAGE_SIZE)?;
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 8affd8262891b..6dc1c2395acaf 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -12,16 +12,16 @@
code::*,
Result, //
},
+ types::{
+ Opaque,
+ Ownable,
+ Owned, //
+ },
uaccess::UserSliceReader, //
};
-use core::{
- marker::PhantomData,
- mem::ManuallyDrop,
- ops::Deref,
- ptr::{
- self,
- NonNull, //
- }, //
+use core::ptr::{
+ self,
+ NonNull, //
};
/// A bitwise shift for the page size.
@@ -65,93 +65,29 @@ pub const fn page_align(addr: usize) -> Option<usize> {
Some(sum & PAGE_MASK)
}
-/// Representation of a non-owning reference to a [`Page`].
-///
-/// This type provides a borrowed version of a [`Page`] that is owned by some other entity, e.g. a
-/// [`Vmalloc`] allocation such as [`VBox`].
-///
-/// # Example
-///
-/// ```
-/// # use kernel::{bindings, prelude::*};
-/// use kernel::page::{BorrowedPage, Page, PAGE_SIZE};
-/// # use core::{mem::MaybeUninit, ptr, ptr::NonNull };
-///
-/// fn borrow_page<'a>(vbox: &'a mut VBox<MaybeUninit<[u8; PAGE_SIZE]>>) -> BorrowedPage<'a> {
-/// let ptr = ptr::from_ref(&**vbox);
-///
-/// // SAFETY: `ptr` is a valid pointer to `Vmalloc` memory.
-/// let page = unsafe { bindings::vmalloc_to_page(ptr.cast()) };
-///
-/// // SAFETY: `vmalloc_to_page` returns a valid pointer to a `struct page` for a valid
-/// // pointer to `Vmalloc` memory.
-/// let page = unsafe { NonNull::new_unchecked(page) };
-///
-/// // SAFETY:
-/// // - `self.0` is a valid pointer to a `struct page`.
-/// // - `self.0` is valid for the entire lifetime of `self`.
-/// unsafe { BorrowedPage::from_raw(page) }
-/// }
-///
-/// let mut vbox = VBox::<[u8; PAGE_SIZE]>::new_uninit(GFP_KERNEL)?;
-/// let page = borrow_page(&mut vbox);
-///
-/// // SAFETY: There is no concurrent read or write to this page.
-/// unsafe { page.fill_zero_raw(0, PAGE_SIZE)? };
-/// # Ok::<(), Error>(())
-/// ```
-///
-/// # Invariants
-///
-/// The borrowed underlying pointer to a `struct page` is valid for the entire lifetime `'a`.
-///
-/// [`VBox`]: kernel::alloc::VBox
-/// [`Vmalloc`]: kernel::alloc::allocator::Vmalloc
-pub struct BorrowedPage<'a>(ManuallyDrop<Page>, PhantomData<&'a Page>);
-
-impl<'a> BorrowedPage<'a> {
- /// Constructs a [`BorrowedPage`] from a raw pointer to a `struct page`.
- ///
- /// # Safety
- ///
- /// - `ptr` must point to a valid `bindings::page`.
- /// - `ptr` must remain valid for the entire lifetime `'a`.
- pub unsafe fn from_raw(ptr: NonNull<bindings::page>) -> Self {
- let page = Page { page: ptr };
-
- // INVARIANT: The safety requirements guarantee that `ptr` is valid for the entire lifetime
- // `'a`.
- Self(ManuallyDrop::new(page), PhantomData)
- }
-}
-
-impl<'a> Deref for BorrowedPage<'a> {
- type Target = Page;
-
- fn deref(&self) -> &Self::Target {
- &self.0
- }
-}
-
-/// Trait to be implemented by types which provide an [`Iterator`] implementation of
-/// [`BorrowedPage`] items, such as [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
+/// Trait to be implemented by types which provide an [`Iterator`] of [`Page`] references, such as
+/// [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
pub trait AsPageIter {
/// The [`Iterator`] type, e.g. [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
- type Iter<'a>: Iterator<Item = BorrowedPage<'a>>
+ type Iter<'a>: Iterator<Item = &'a Page>
where
Self: 'a;
- /// Returns an [`Iterator`] of [`BorrowedPage`] items over all pages owned by `self`.
+ /// Returns an [`Iterator`] of [`Page`] references over all pages owned by `self`.
fn page_iter(&mut self) -> Self::Iter<'_>;
}
-/// A pointer to a page that owns the page allocation.
+/// A `struct page`.
+///
+/// A `Page` is accessed through a shared reference or through an owning [`Owned<Page>`]; the latter
+/// frees the page allocation when it is dropped.
///
/// # Invariants
///
-/// The pointer is valid, and has ownership over the page.
+/// The `Page` is backed by a valid `struct page`.
+#[repr(transparent)]
pub struct Page {
- page: NonNull<bindings::page>,
+ page: Opaque<bindings::page>,
}
// SAFETY: Pages have no logic that relies on them staying on a given thread, so moving them across
@@ -185,19 +121,20 @@ impl Page {
/// # Ok::<(), kernel::alloc::AllocError>(())
/// ```
#[inline]
- pub fn alloc_page(flags: Flags) -> Result<Self, AllocError> {
+ pub fn alloc_page(flags: Flags) -> Result<Owned<Self>, AllocError> {
// SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
// is always safe to call this method.
let page = unsafe { bindings::alloc_pages(flags.as_raw(), 0) };
let page = NonNull::new(page).ok_or(AllocError)?;
- // INVARIANT: We just successfully allocated a page, so we now have ownership of the newly
- // allocated page. We transfer that ownership to the new `Page` object.
- Ok(Self { page })
+ // SAFETY: We just successfully allocated a page, so we now have ownership of the newly
+ // allocated page. We transfer that ownership to the new `Owned<Page>` object.
+ // Since `Page` is transparent, we can cast the pointer directly.
+ Ok(unsafe { Owned::from_raw(page.cast()) })
}
/// Returns a raw pointer to the page.
pub fn as_ptr(&self) -> *mut bindings::page {
- self.page.as_ptr()
+ Opaque::cast_into(&self.page)
}
/// Get the node id containing this page.
@@ -372,10 +309,11 @@ pub unsafe fn copy_from_user_slice_raw(
}
}
-impl Drop for Page {
+impl Ownable for Page {
#[inline]
- fn drop(&mut self) {
- // SAFETY: By the type invariants, we have ownership of the page and can free it.
- unsafe { bindings::__free_pages(self.page.as_ptr(), 0) };
+ unsafe fn release(this: NonNull<Self>) {
+ // SAFETY: By the function safety requirements, we have ownership of the page and can free
+ // it. Since Page is transparent, we can cast the raw pointer directly.
+ unsafe { bindings::__free_pages(this.as_ptr().cast(), 0) };
}
}
--
2.51.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* Re: [PATCH v18 4/8] rust: page: convert to `Ownable`
2026-06-25 10:15 ` [PATCH v18 4/8] rust: page: convert to `Ownable` Andreas Hindborg
@ 2026-06-25 13:32 ` Gary Guo
0 siblings, 0 replies; 12+ messages in thread
From: Gary Guo @ 2026-06-25 13:32 UTC (permalink / raw)
To: Andreas Hindborg, Danilo Krummrich, Lorenzo Stoakes,
Vlastimil Babka, Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda,
Boqun Feng, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, Lyude Paul,
Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Christian Brauner, Carlos Llamas, Rafael J. Wysocki, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
David Airlie, Simona Vetter, Alexander Viro, Jan Kara,
Igor Korotin, Viresh Kumar, Nishanth Menon, Stephen Boyd,
Bjorn Helgaas, Krzysztof Wilczyński, Pavel Tikhomirov,
Michal Wilczynski
Cc: Philipp Stanner, rust-for-linux, linux-kernel, linux-mm,
driver-core, linux-block, linux-security-module, dri-devel,
linux-fsdevel, linux-pm, linux-pci, linux-pwm, Asahi Lina
On Thu Jun 25, 2026 at 11:15 AM BST, Andreas Hindborg wrote:
> From: Asahi Lina <lina@asahilina.net>
>
> This allows Page references to be returned as borrowed references,
> without necessarily owning the struct page.
>
> Remove `BorrowedPage` and update users to use `Owned<Page>`.
>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> [ Andreas: Fix formatting and add a safety comment, update users. ]
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
Nice to see `BorrowedPage` going away.
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> drivers/android/binder/page_range.rs | 10 +--
> rust/kernel/alloc/allocator.rs | 19 +++---
> rust/kernel/alloc/allocator/iter.rs | 6 +-
> rust/kernel/page.rs | 122 +++++++++--------------------------
> 4 files changed, 46 insertions(+), 111 deletions(-)
^ permalink raw reply [flat|nested] 12+ messages in thread
* [PATCH v18 5/8] rust: rename `AlwaysRefCounted` to `RefCounted`.
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
` (3 preceding siblings ...)
2026-06-25 10:15 ` [PATCH v18 4/8] rust: page: convert to `Ownable` Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 6/8] rust: Add missing SAFETY documentation for `ARef` example Andreas Hindborg
` (2 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Oliver Mangold, Viresh Kumar, Igor Korotin
From: Oliver Mangold <oliver.mangold@pm.me>
There are types where it may both be reference counted in some cases and
owned in others. In such cases, obtaining `ARef<T>` from `&T` would be
unsound as it allows creation of `ARef<T>` copy from `&Owned<T>`.
Therefore, we split `AlwaysRefCounted` into `RefCounted` (which `ARef<T>`
would require) and a marker trait to indicate that the type is always
reference counted (and not `Ownable`) so the `&T` -> `ARef<T>` conversion
is possible.
- Rename `AlwaysRefCounted` to `RefCounted`.
- Add a new unsafe trait `AlwaysRefCounted`.
- Implement the new trait `AlwaysRefCounted` for the newly renamed
`RefCounted` implementations. This leaves functionality of existing
implementers of `AlwaysRefCounted` intact.
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
[ Andreas: Updated commit message and rebase on rust-next (7.2) ]
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/auxiliary.rs | 10 +++++++-
rust/kernel/block/mq/request.rs | 19 +++++++++-----
rust/kernel/cred.rs | 16 ++++++++++--
rust/kernel/device.rs | 12 +++++++--
rust/kernel/device/property.rs | 11 ++++++--
rust/kernel/drm/device.rs | 9 +++++--
rust/kernel/drm/gem/mod.rs | 16 +++++++++---
rust/kernel/fs/file.rs | 23 ++++++++++++++---
rust/kernel/i2c.rs | 13 +++++++---
rust/kernel/mm.rs | 22 +++++++++++++---
rust/kernel/mm/mmput_async.rs | 12 +++++++--
rust/kernel/opp.rs | 16 +++++++++---
rust/kernel/owned.rs | 2 +-
rust/kernel/pci.rs | 10 +++++++-
rust/kernel/pid_namespace.rs | 15 +++++++++--
rust/kernel/platform.rs | 10 +++++++-
rust/kernel/pwm.rs | 12 +++++++--
rust/kernel/sync/aref.rs | 57 +++++++++++++++++++++++++----------------
rust/kernel/task.rs | 13 ++++++++--
rust/kernel/types.rs | 12 ++++++---
rust/kernel/usb.rs | 17 +++++++++---
21 files changed, 255 insertions(+), 72 deletions(-)
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index c42928d5a2393..854525289c8b4 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -19,6 +19,10 @@
to_result, //
},
prelude::*,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::{
ForLt,
ForeignOwnable,
@@ -344,7 +348,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx>
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -363,6 +367,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs
index ce3e30c81cb5e..8dad15ae4cfb0 100644
--- a/rust/kernel/block/mq/request.rs
+++ b/rust/kernel/block/mq/request.rs
@@ -9,7 +9,11 @@
block::mq::Operations,
error::Result,
sync::{
- aref::{ARef, AlwaysRefCounted},
+ aref::{
+ ARef,
+ AlwaysRefCounted,
+ RefCounted, //
+ },
atomic::Relaxed,
Refcount,
},
@@ -229,11 +233,10 @@ unsafe impl<T: Operations> Send for Request<T> {}
// mutate `self` are internally synchronized`
unsafe impl<T: Operations> Sync for Request<T> {}
-// SAFETY: All instances of `Request<T>` are reference counted. This
-// implementation of `AlwaysRefCounted` ensure that increments to the ref count
-// keeps the object alive in memory at least until a matching reference count
-// decrement is executed.
-unsafe impl<T: Operations> AlwaysRefCounted for Request<T> {
+// SAFETY: All instances of `Request<T>` are reference counted. This implementation of `RefCounted`
+// ensure that increments to the ref count keeps the object alive in memory at least until a
+// matching reference count decrement is executed.
+unsafe impl<T: Operations> RefCounted for Request<T> {
fn inc_ref(&self) {
self.wrapper_ref().refcount().inc();
}
@@ -255,3 +258,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
}
}
}
+
+// SAFETY: We currently do not implement `Ownable`, thus it is okay to obtain an `ARef<Request>`
+// from a `&Request` (but this will change in the future).
+unsafe impl<T: Operations> AlwaysRefCounted for Request<T> {}
diff --git a/rust/kernel/cred.rs b/rust/kernel/cred.rs
index ffa156b9df377..b17736a9adcd5 100644
--- a/rust/kernel/cred.rs
+++ b/rust/kernel/cred.rs
@@ -8,7 +8,15 @@
//!
//! Reference: <https://www.kernel.org/doc/html/latest/security/credentials.html>
-use crate::{bindings, sync::aref::AlwaysRefCounted, task::Kuid, types::Opaque};
+use crate::{
+ bindings,
+ sync::aref::RefCounted,
+ task::Kuid,
+ types::{
+ AlwaysRefCounted,
+ Opaque, //
+ }, //
+};
/// Wraps the kernel's `struct cred`.
///
@@ -76,7 +84,7 @@ pub fn euid(&self) -> Kuid {
}
// SAFETY: The type invariants guarantee that `Credential` is always ref-counted.
-unsafe impl AlwaysRefCounted for Credential {
+unsafe impl RefCounted for Credential {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -90,3 +98,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Credential>) {
unsafe { bindings::put_cred(obj.cast().as_ptr()) };
}
}
+
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Credential>` from a
+// `&Credential`.
+unsafe impl AlwaysRefCounted for Credential {}
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 645afc49a27d6..2e90f6a06fd05 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -8,8 +8,12 @@
bindings,
fmt,
prelude::*,
- sync::aref::ARef,
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
types::{
+ AlwaysRefCounted,
ForeignOwnable,
Opaque, //
}, //
@@ -448,7 +452,7 @@ pub fn name(&self) -> &CStr {
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_raw()) };
@@ -460,6 +464,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
// SAFETY: As by the type invariant `Device` can be sent to any thread.
unsafe impl Send for Device {}
diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs
index 5aead835fbbc0..cee7e25013689 100644
--- a/rust/kernel/device/property.rs
+++ b/rust/kernel/device/property.rs
@@ -14,7 +14,10 @@
fmt,
prelude::*,
str::{CStr, CString},
- sync::aref::ARef,
+ sync::aref::{
+ ARef,
+ AlwaysRefCounted, //
+ },
types::Opaque,
};
@@ -360,7 +363,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
}
// SAFETY: Instances of `FwNode` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for FwNode {
+unsafe impl crate::sync::aref::RefCounted for FwNode {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the
// refcount is non-zero.
@@ -374,6 +377,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<FwNode>` from a
+// `&FwNode`.
+unsafe impl AlwaysRefCounted for FwNode {}
+
enum Node<'a> {
Borrowed(&'a FwNode),
Owned(ARef<FwNode>),
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 403fc35353c74..368742a258376 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -15,7 +15,8 @@
prelude::*,
sync::aref::{
ARef,
- AlwaysRefCounted, //
+ AlwaysRefCounted,
+ RefCounted, //
},
types::Opaque,
workqueue::{
@@ -227,7 +228,7 @@ fn deref(&self) -> &Self::Target {
// SAFETY: DRM device objects are always reference counted and the get/put functions
// satisfy the requirements.
-unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {
+unsafe impl<T: drm::Driver> RefCounted for Device<T> {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::drm_dev_get(self.as_raw()) };
@@ -242,6 +243,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {}
+
impl<T: drm::Driver> AsRef<device::Device> for Device<T> {
fn as_ref(&self) -> &device::Device {
// SAFETY: `bindings::drm_device::dev` is valid as long as the DRM device itself is valid,
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 01b5bd47a3332..30d3718578fe8 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -17,7 +17,7 @@
prelude::*,
sync::aref::{
ARef,
- AlwaysRefCounted, //
+ RefCounted, //
},
types::Opaque,
};
@@ -29,7 +29,7 @@
#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
pub mod shmem;
-/// A macro for implementing [`AlwaysRefCounted`] for any GEM object type.
+/// A macro for implementing [`RefCounted`] for any GEM object type.
///
/// Since all GEM objects use the same refcounting scheme.
#[macro_export]
@@ -42,7 +42,7 @@ impl $( <$( $tparam_id:ident ),+> )? for $type:ty
)?
) => {
// SAFETY: All GEM objects are refcounted.
- unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $type
+ unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::RefCounted for $type
where
Self: IntoGEMObject,
$( $( $bind_param : $bind_trait ),+ )?
@@ -61,6 +61,14 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
unsafe { bindings::drm_gem_object_put(obj) };
}
}
+
+ // SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<$type>` from a
+ // `&$type`.
+ unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $type
+ where
+ Self: IntoGEMObject,
+ $( $( $bind_param : $bind_trait ),+ )?
+ {}
};
}
#[cfg_attr(not(CONFIG_RUST_DRM_GEM_SHMEM_HELPER), allow(unused))]
@@ -98,7 +106,7 @@ fn close(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>)
}
/// Trait that represents a GEM object subtype
-pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted {
+pub trait IntoGEMObject: Sized + super::private::Sealed + RefCounted {
/// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as
/// this owning object is valid.
fn as_raw(&self) -> *mut bindings::drm_gem_object;
diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 23ee689bd2400..720e57418358d 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -12,8 +12,15 @@
cred::Credential,
error::{code::*, to_result, Error, Result},
fmt,
- sync::aref::{ARef, AlwaysRefCounted},
- types::{NotThreadSafe, Opaque},
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::{
+ AlwaysRefCounted,
+ NotThreadSafe,
+ Opaque, //
+ }, //
};
use core::ptr;
@@ -197,7 +204,7 @@ unsafe impl Sync for File {}
// SAFETY: The type invariants guarantee that `File` is always ref-counted. This implementation
// makes `ARef<File>` own a normal refcount.
-unsafe impl AlwaysRefCounted for File {
+unsafe impl RefCounted for File {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -212,6 +219,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<File>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<File>` from a
+// `&File`.
+unsafe impl AlwaysRefCounted for File {}
+
/// Wraps the kernel's `struct file`. Not thread safe.
///
/// This type represents a file that is not known to be safe to transfer across thread boundaries.
@@ -233,7 +244,7 @@ pub struct LocalFile {
// SAFETY: The type invariants guarantee that `LocalFile` is always ref-counted. This implementation
// makes `ARef<LocalFile>` own a normal refcount.
-unsafe impl AlwaysRefCounted for LocalFile {
+unsafe impl RefCounted for LocalFile {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -249,6 +260,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<LocalFile>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<LocalFile>` from a
+// `&LocalFile`.
+unsafe impl AlwaysRefCounted for LocalFile {}
+
impl LocalFile {
/// Constructs a new `struct file` wrapper from a file descriptor.
///
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 624b971ca8b0b..02b2c9220eb11 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -18,7 +18,8 @@
prelude::*,
sync::aref::{
ARef,
- AlwaysRefCounted, //
+ AlwaysRefCounted,
+ RefCounted, //
},
types::Opaque, //
};
@@ -424,7 +425,7 @@ pub fn get(index: i32) -> Result<ARef<Self>> {
kernel::impl_device_context_into_aref!(I2cAdapter);
// SAFETY: Instances of `I2cAdapter` are always reference-counted.
-unsafe impl AlwaysRefCounted for I2cAdapter {
+unsafe impl RefCounted for I2cAdapter {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::i2c_get_adapter(self.index()) };
@@ -435,6 +436,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
unsafe { bindings::i2c_put_adapter(obj.as_ref().as_raw()) }
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from an
+// `&I2cAdapter`.
+unsafe impl AlwaysRefCounted for I2cAdapter {}
/// The i2c board info representation
///
@@ -500,7 +504,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for I2cClient<C
kernel::impl_device_context_into_aref!(I2cClient);
// SAFETY: Instances of `I2cClient` are always reference-counted.
-unsafe impl AlwaysRefCounted for I2cClient {
+unsafe impl RefCounted for I2cClient {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -511,6 +515,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
unsafe { bindings::put_device(&raw mut (*obj.as_ref().as_raw()).dev) }
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from an
+// `&I2cClient`.
+unsafe impl AlwaysRefCounted for I2cClient {}
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for I2cClient<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs
index 4764d7b68f2a7..83ed94fca14ca 100644
--- a/rust/kernel/mm.rs
+++ b/rust/kernel/mm.rs
@@ -13,8 +13,15 @@
use crate::{
bindings,
- sync::aref::{ARef, AlwaysRefCounted},
- types::{NotThreadSafe, Opaque},
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::{
+ AlwaysRefCounted,
+ NotThreadSafe,
+ Opaque, //
+ }, //
};
use core::{ops::Deref, ptr::NonNull};
@@ -55,7 +62,7 @@ unsafe impl Send for Mm {}
unsafe impl Sync for Mm {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for Mm {
+unsafe impl RefCounted for Mm {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -69,6 +76,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Mm>` from a `&Mm`.
+unsafe impl AlwaysRefCounted for Mm {}
+
/// A wrapper for the kernel's `struct mm_struct`.
///
/// This type is like [`Mm`], but with non-zero `mm_users`. It can only be used when `mm_users` can
@@ -91,7 +101,7 @@ unsafe impl Send for MmWithUser {}
unsafe impl Sync for MmWithUser {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for MmWithUser {
+unsafe impl RefCounted for MmWithUser {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -105,6 +115,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<MmWithUser>` from a
+// `&MmWithUser`.
+unsafe impl AlwaysRefCounted for MmWithUser {}
+
// Make all `Mm` methods available on `MmWithUser`.
impl Deref for MmWithUser {
type Target = Mm;
diff --git a/rust/kernel/mm/mmput_async.rs b/rust/kernel/mm/mmput_async.rs
index b8d2f051225c7..8fbc396e46028 100644
--- a/rust/kernel/mm/mmput_async.rs
+++ b/rust/kernel/mm/mmput_async.rs
@@ -10,7 +10,11 @@
use crate::{
bindings,
mm::MmWithUser,
- sync::aref::{ARef, AlwaysRefCounted},
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::AlwaysRefCounted,
};
use core::{ops::Deref, ptr::NonNull};
@@ -34,7 +38,7 @@ unsafe impl Send for MmWithUserAsync {}
unsafe impl Sync for MmWithUserAsync {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for MmWithUserAsync {
+unsafe impl RefCounted for MmWithUserAsync {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -48,6 +52,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<MmWithUserAsync>`
+// from a `&MmWithUserAsync`.
+unsafe impl AlwaysRefCounted for MmWithUserAsync {}
+
// Make all `MmWithUser` methods available on `MmWithUserAsync`.
impl Deref for MmWithUserAsync {
type Target = MmWithUser;
diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs
index 62e44676125d1..b8db6bdefd077 100644
--- a/rust/kernel/opp.rs
+++ b/rust/kernel/opp.rs
@@ -16,8 +16,14 @@
ffi::{c_char, c_ulong},
prelude::*,
str::CString,
- sync::aref::{ARef, AlwaysRefCounted},
- types::Opaque,
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::{
+ AlwaysRefCounted,
+ Opaque, //
+ }, //
};
#[cfg(CONFIG_CPU_FREQ)]
@@ -1041,7 +1047,7 @@ unsafe impl Send for OPP {}
unsafe impl Sync for OPP {}
/// SAFETY: The type invariants guarantee that [`OPP`] is always refcounted.
-unsafe impl AlwaysRefCounted for OPP {
+unsafe impl RefCounted for OPP {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -1055,6 +1061,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<OPP>` from an
+// `&OPP`.
+unsafe impl AlwaysRefCounted for OPP {}
+
impl OPP {
/// Creates an owned reference to a [`OPP`] from a valid pointer.
///
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index 9c92d4a83cc1b..e79936c00002c 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -27,7 +27,7 @@
///
/// Note: The underlying object is not required to provide internal reference counting, because it
/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
-/// [`AlwaysRefCounted`](crate::sync::aref::AlwaysRefCounted) should be implemented.
+/// [`RefCounted`](crate::types::RefCounted) should be implemented.
///
/// # Examples
///
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 5071cae6543fd..ea9ef99cecb07 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -19,6 +19,10 @@
},
prelude::*,
str::CStr,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque,
ThisModule, //
};
@@ -481,7 +485,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx>
impl<'a> crate::dma::Device<'a> for Device<device::Core<'a>> {}
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::pci_dev_get(self.as_raw()) };
@@ -493,6 +497,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/pid_namespace.rs b/rust/kernel/pid_namespace.rs
index 979a9718f153d..067f68b99e8c5 100644
--- a/rust/kernel/pid_namespace.rs
+++ b/rust/kernel/pid_namespace.rs
@@ -7,7 +7,14 @@
//! C header: [`include/linux/pid_namespace.h`](srctree/include/linux/pid_namespace.h) and
//! [`include/linux/pid.h`](srctree/include/linux/pid.h)
-use crate::{bindings, sync::aref::AlwaysRefCounted, types::Opaque};
+use crate::{
+ bindings,
+ sync::aref::RefCounted,
+ types::{
+ AlwaysRefCounted,
+ Opaque, //
+ }, //
+};
use core::ptr;
/// Wraps the kernel's `struct pid_namespace`. Thread safe.
@@ -41,7 +48,7 @@ pub unsafe fn from_ptr<'a>(ptr: *const bindings::pid_namespace) -> &'a Self {
}
// SAFETY: Instances of `PidNamespace` are always reference-counted.
-unsafe impl AlwaysRefCounted for PidNamespace {
+unsafe impl RefCounted for PidNamespace {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -55,6 +62,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<PidNamespace>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<PidNamespace>` from
+// a `&PidNamespace`.
+unsafe impl AlwaysRefCounted for PidNamespace {}
+
// SAFETY:
// - `PidNamespace::dec_ref` can be called from any thread.
// - It is okay to send ownership of `PidNamespace` across thread boundaries.
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 9b362e0495d32..0ba676445b06d 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -27,6 +27,10 @@
},
of,
prelude::*,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque,
ThisModule, //
};
@@ -518,7 +522,7 @@ pub fn optional_irq_by_name(&self, name: &CStr) -> Result<IrqRequest<'_>> {
impl<'a> crate::dma::Device<'a> for Device<device::Core<'a>> {}
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -530,6 +534,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/pwm.rs b/rust/kernel/pwm.rs
index 6c9d667009ef7..2d1cd74dd98e1 100644
--- a/rust/kernel/pwm.rs
+++ b/rust/kernel/pwm.rs
@@ -13,7 +13,11 @@
devres,
error::{self, to_result},
prelude::*,
- sync::aref::{ARef, AlwaysRefCounted},
+ sync::aref::{
+ ARef,
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque, //
};
use core::{
@@ -629,7 +633,7 @@ pub fn new<'a>(
}
// SAFETY: Implements refcounting for `Chip` using the embedded `struct device`.
-unsafe impl<T: PwmOps> AlwaysRefCounted for Chip<T> {
+unsafe impl<T: PwmOps> RefCounted for Chip<T> {
#[inline]
fn inc_ref(&self) {
// SAFETY: `self.0.get()` points to a valid `pwm_chip` because `self` exists.
@@ -647,6 +651,10 @@ unsafe fn dec_ref(obj: NonNull<Chip<T>>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Chip<T>>` from a
+// `&Chip<T>`.
+unsafe impl<T: PwmOps> AlwaysRefCounted for Chip<T> {}
+
// SAFETY: `Chip` is a wrapper around `*mut bindings::pwm_chip`. The underlying C
// structure's state is managed and synchronized by the kernel's device model
// and PWM core locking mechanisms. Therefore, it is safe to move the `Chip`
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index 3bd5eb8a1a526..fb7466a362741 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -24,11 +24,9 @@
ptr::NonNull, //
};
-/// Types that are _always_ reference counted.
+/// Types that are internally reference counted.
///
/// It allows such types to define their own custom ref increment and decrement functions.
-/// Additionally, it allows users to convert from a shared reference `&T` to an owned reference
-/// [`ARef<T>`].
///
/// This is usually implemented by wrappers to existing structures on the C side of the code. For
/// Rust code, the recommendation is to use [`Arc`](crate::sync::Arc) to create reference-counted
@@ -45,9 +43,8 @@
/// at least until matching decrements are performed.
///
/// Implementers must also ensure that all instances are reference-counted. (Otherwise they
-/// won't be able to honour the requirement that [`AlwaysRefCounted::inc_ref`] keep the object
-/// alive.)
-pub unsafe trait AlwaysRefCounted {
+/// won't be able to honour the requirement that [`RefCounted::inc_ref`] keep the object alive.)
+pub unsafe trait RefCounted {
/// Increments the reference count on the object.
fn inc_ref(&self);
@@ -60,11 +57,27 @@ pub unsafe trait AlwaysRefCounted {
/// Callers must ensure that there was a previous matching increment to the reference count,
/// and that the object is no longer used after its reference count is decremented (as it may
/// result in the object being freed), unless the caller owns another increment on the refcount
- /// (e.g., it calls [`AlwaysRefCounted::inc_ref`] twice, then calls
- /// [`AlwaysRefCounted::dec_ref`] once).
+ /// (e.g., it calls [`RefCounted::inc_ref`] twice, then calls [`RefCounted::dec_ref`] once).
unsafe fn dec_ref(obj: NonNull<Self>);
}
+/// Always reference-counted type.
+///
+/// It allows deriving a counted reference [`ARef<T>`] from a `&T`.
+///
+/// This provides some convenience, but it allows "escaping" borrow checks on `&T`. As it
+/// complicates attempts to ensure that a reference to T is unique, it is optional to provide for
+/// [`RefCounted`] types. See *Safety* below.
+///
+/// # Safety
+///
+/// Implementers must ensure that no safety invariants are violated by upgrading an `&T` to an
+/// [`ARef<T>`]. In particular that implies [`AlwaysRefCounted`] and [`crate::types::Ownable`]
+/// cannot be implemented for the same type, as this would allow violating the uniqueness guarantee
+/// of [`crate::types::Owned<T>`] by dereferencing it into an `&T` and obtaining an [`ARef`] from
+/// that.
+pub unsafe trait AlwaysRefCounted: RefCounted {}
+
/// An owned reference to an always-reference-counted object.
///
/// The object's reference count is automatically decremented when an instance of [`ARef`] is
@@ -75,7 +88,7 @@ pub unsafe trait AlwaysRefCounted {
///
/// The pointer stored in `ptr` is non-null and valid for the lifetime of the [`ARef`] instance. In
/// particular, the [`ARef`] instance owns an increment on the underlying object's reference count.
-pub struct ARef<T: AlwaysRefCounted> {
+pub struct ARef<T: RefCounted> {
ptr: NonNull<T>,
_p: PhantomData<T>,
}
@@ -84,19 +97,19 @@ pub struct ARef<T: AlwaysRefCounted> {
// it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
// `T` to be `Send` because any thread that has an `ARef<T>` may ultimately access `T` using a
// mutable reference, for example, when the reference count reaches zero and `T` is dropped.
-unsafe impl<T: AlwaysRefCounted + Sync + Send> Send for ARef<T> {}
+unsafe impl<T: RefCounted + Sync + Send> Send for ARef<T> {}
// SAFETY: It is safe to send `&ARef<T>` to another thread when the underlying `T` is `Sync`
// because it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally,
// it needs `T` to be `Send` because any thread that has a `&ARef<T>` may clone it and get an
// `ARef<T>` on that thread, so the thread may ultimately access `T` using a mutable reference, for
// example, when the reference count reaches zero and `T` is dropped.
-unsafe impl<T: AlwaysRefCounted + Sync + Send> Sync for ARef<T> {}
+unsafe impl<T: RefCounted + Sync + Send> Sync for ARef<T> {}
// Even if `T` is pinned, pointers to `T` can still move.
-impl<T: AlwaysRefCounted> Unpin for ARef<T> {}
+impl<T: RefCounted> Unpin for ARef<T> {}
-impl<T: AlwaysRefCounted> ARef<T> {
+impl<T: RefCounted> ARef<T> {
/// Creates a new instance of [`ARef`].
///
/// It takes over an increment of the reference count on the underlying object.
@@ -125,12 +138,12 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// ```
/// use core::ptr::NonNull;
- /// use kernel::sync::aref::{ARef, AlwaysRefCounted};
+ /// use kernel::sync::aref::{ARef, RefCounted};
///
/// struct Empty {}
///
/// # // SAFETY: TODO.
- /// unsafe impl AlwaysRefCounted for Empty {
+ /// unsafe impl RefCounted for Empty {
/// fn inc_ref(&self) {}
/// unsafe fn dec_ref(_obj: NonNull<Self>) {}
/// }
@@ -148,7 +161,7 @@ pub fn into_raw(me: Self) -> NonNull<T> {
}
}
-impl<T: AlwaysRefCounted> Clone for ARef<T> {
+impl<T: RefCounted> Clone for ARef<T> {
fn clone(&self) -> Self {
self.inc_ref();
// SAFETY: We just incremented the refcount above.
@@ -156,7 +169,7 @@ fn clone(&self) -> Self {
}
}
-impl<T: AlwaysRefCounted> Deref for ARef<T> {
+impl<T: RefCounted> Deref for ARef<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
@@ -173,7 +186,7 @@ fn from(b: &T) -> Self {
}
}
-impl<T: AlwaysRefCounted> Drop for ARef<T> {
+impl<T: RefCounted> Drop for ARef<T> {
fn drop(&mut self) {
// SAFETY: The type invariants guarantee that the `ARef` owns the reference we're about to
// decrement.
@@ -183,19 +196,19 @@ fn drop(&mut self) {
impl<T, U> PartialEq<ARef<U>> for ARef<T>
where
- T: AlwaysRefCounted + PartialEq<U>,
- U: AlwaysRefCounted,
+ T: RefCounted + PartialEq<U>,
+ U: RefCounted,
{
#[inline]
fn eq(&self, other: &ARef<U>) -> bool {
T::eq(&**self, &**other)
}
}
-impl<T: AlwaysRefCounted + Eq> Eq for ARef<T> {}
+impl<T: RefCounted + Eq> Eq for ARef<T> {}
impl<T, U> PartialEq<&'_ U> for ARef<T>
where
- T: AlwaysRefCounted + PartialEq<U>,
+ T: RefCounted + PartialEq<U>,
{
#[inline]
fn eq(&self, other: &&U) -> bool {
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 38273f4eedb51..6259430b0ca31 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -10,7 +10,12 @@
pid_namespace::PidNamespace,
prelude::*,
sync::aref::ARef,
- types::{NotThreadSafe, Opaque},
+ types::{
+ AlwaysRefCounted,
+ NotThreadSafe,
+ Opaque,
+ RefCounted, //
+ },
};
use core::{
ops::Deref,
@@ -347,7 +352,7 @@ pub fn group_leader(&self) -> &Task {
}
// SAFETY: The type invariants guarantee that `Task` is always refcounted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Task {
+unsafe impl RefCounted for Task {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -361,6 +366,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Task>` from a
+// `&Task`.
+unsafe impl AlwaysRefCounted for Task {}
+
impl PartialEq for Task {
#[inline]
fn eq(&self, other: &Self) -> bool {
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index c41eab0ec983c..5ef763717e59a 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -15,9 +15,15 @@
pub mod for_lt;
pub use for_lt::ForLt;
-pub use crate::owned::{
- Ownable,
- Owned, //
+pub use crate::{
+ owned::{
+ Ownable,
+ Owned, //
+ },
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ }, //
};
/// Used to transfer ownership to and from foreign (non-Rust) languages.
diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index 7aff0c82d0afc..59350c6b0df2a 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -18,7 +18,10 @@
to_result, //
},
prelude::*,
- sync::aref::AlwaysRefCounted,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque,
ThisModule, //
};
@@ -392,7 +395,7 @@ fn as_ref(&self) -> &Device {
}
// SAFETY: Instances of `Interface` are always reference-counted.
-unsafe impl AlwaysRefCounted for Interface {
+unsafe impl RefCounted for Interface {
fn inc_ref(&self) {
// SAFETY: The invariants of `Interface` guarantee that `self.as_raw()`
// returns a valid `struct usb_interface` pointer, for which we will
@@ -406,6 +409,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Interface>` from a
+// `&Interface`.
+unsafe impl AlwaysRefCounted for Interface {}
+
// SAFETY: A `Interface` is always reference-counted and can be released from any thread.
unsafe impl Send for Interface {}
@@ -443,7 +450,7 @@ fn as_raw(&self) -> *mut bindings::usb_device {
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The invariants of `Device` guarantee that `self.as_raw()`
// returns a valid `struct usb_device` pointer, for which we will
@@ -457,6 +464,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
--
2.51.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v18 6/8] rust: Add missing SAFETY documentation for `ARef` example
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
` (4 preceding siblings ...)
2026-06-25 10:15 ` [PATCH v18 5/8] rust: rename `AlwaysRefCounted` to `RefCounted` Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 7/8] rust: Add `OwnableRefCounted` Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 8/8] rust: page: add `from_raw()` Andreas Hindborg
7 siblings, 0 replies; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Oliver Mangold
From: Oliver Mangold <oliver.mangold@pm.me>
SAFETY comment in rustdoc example was just 'TODO'. Fixed.
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/sync/aref.rs | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index fb7466a362741..d0865aeb9371b 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -142,7 +142,9 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// struct Empty {}
///
- /// # // SAFETY: TODO.
+ /// // SAFETY: The `RefCounted` implementation for `Empty` does not count references and never
+ /// // frees the underlying object. Thus we can act as owning an increment on the refcount for
+ /// // the object that we pass to the newly created `ARef`.
/// unsafe impl RefCounted for Empty {
/// fn inc_ref(&self) {}
/// unsafe fn dec_ref(_obj: NonNull<Self>) {}
@@ -150,7 +152,7 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// let mut data = Empty {};
/// let ptr = NonNull::<Empty>::new(&mut data).unwrap();
- /// # // SAFETY: TODO.
+ /// // SAFETY: We keep `data` around longer than the `ARef`.
/// let data_ref: ARef<Empty> = unsafe { ARef::from_raw(ptr) };
/// let raw_ptr: NonNull<Empty> = ARef::into_raw(data_ref);
///
--
2.51.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v18 7/8] rust: Add `OwnableRefCounted`
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
` (5 preceding siblings ...)
2026-06-25 10:15 ` [PATCH v18 6/8] rust: Add missing SAFETY documentation for `ARef` example Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
2026-06-25 10:15 ` [PATCH v18 8/8] rust: page: add `from_raw()` Andreas Hindborg
7 siblings, 0 replies; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Oliver Mangold
From: Oliver Mangold <oliver.mangold@pm.me>
Types implementing one of these traits can safely convert between an
`ARef<T>` and an `Owned<T>`.
This is useful for types which generally are accessed through an `ARef`
but have methods which can only safely be called when the reference is
unique, like e.g. `block::mq::Request::end_ok()`.
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
[ Andreas: Fix formatting, update documentation, fix error handling in
examples. ]
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/owned.rs | 140 +++++++++++++++++++++++++++++++++++++++++++++--
rust/kernel/sync/aref.rs | 16 +++++-
rust/kernel/types.rs | 1 +
3 files changed, 151 insertions(+), 6 deletions(-)
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index e79936c00002c..bb4223c0f725a 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -14,20 +14,26 @@
pin::Pin,
ptr::NonNull, //
};
+use kernel::{
+ sync::aref::ARef,
+ types::RefCounted, //
+};
use kernel::types::ForeignOwnable;
/// Types that specify their own way of performing allocation and destruction. Typically, this trait
/// is implemented on types from the C side.
///
-/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type. This
-/// is useful when it is desirable to tie the lifetime of the reference to an owned object, rather
-/// than pass around a bare reference. [`Ownable`] types can define custom drop logic that is
-/// executed when the owned reference [`Owned<Self>`] pointing to the object is dropped.
+/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type.
+/// - This is useful when it is desirable to tie the lifetime of an object reference to an owned
+/// object, rather than pass around a bare reference.
+/// - [`Ownable`] types can define custom drop logic that is executed when the owned reference
+/// of type [`Owned<_>`] pointing to the object is dropped.
///
/// Note: The underlying object is not required to provide internal reference counting, because it
/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
-/// [`RefCounted`](crate::types::RefCounted) should be implemented.
+/// [`RefCounted`] should be implemented. [`OwnableRefCounted`] should be implemented if conversion
+/// between unique and shared (reference counted) ownership is needed.
///
/// # Examples
///
@@ -239,3 +245,127 @@ unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a>
unsafe { Pin::new_unchecked(inner) }
}
}
+
+/// A trait for objects that can be wrapped in either one of the reference types [`Owned`] and
+/// [`ARef`].
+///
+/// # Examples
+///
+/// A minimal example implementation of [`OwnableRefCounted`], [`Ownable`] and its usage with
+/// [`ARef`] and [`Owned`] looks like this:
+///
+/// ```
+/// # #![expect(clippy::disallowed_names)]
+/// # use core::cell::Cell;
+/// # use core::ptr::NonNull;
+/// # use kernel::alloc::{flags, kbox::KBox, AllocError};
+/// # use kernel::sync::aref::{ARef, RefCounted};
+/// # use kernel::types::{Owned, Ownable, OwnableRefCounted};
+///
+/// // An internally refcounted struct for demonstration purposes.
+/// //
+/// // # Invariants
+/// //
+/// // - `refcount` is always non-zero for a valid object.
+/// // - `refcount` is >1 if there is more than one Rust reference to it.
+/// //
+/// struct Foo {
+/// refcount: Cell<usize>,
+/// }
+///
+/// impl Foo {
+/// fn new() -> Result<Owned<Self>> {
+/// // We are just using a `KBox` here to handle the actual allocation, as our `Foo` is
+/// // not actually a C-allocated object.
+/// // INVARIANT: We initialize `refcount` to 1, satisfying the invariants.
+/// let result = KBox::new(
+/// Foo {
+/// refcount: Cell::new(1),
+/// },
+/// flags::GFP_KERNEL,
+/// )?;
+/// let result = KBox::into_non_null(result);
+/// // SAFETY:
+/// // - We just allocated the `Self`, thus it is valid and we own it.
+/// // - We can transfer this ownership to the `from_raw` method.
+/// Ok(unsafe { Owned::from_raw(result) })
+/// }
+/// }
+///
+/// // SAFETY: We increment and decrement each time the respective function is called and only free
+/// // the `Foo` when the refcount reaches zero.
+/// unsafe impl RefCounted for Foo {
+/// fn inc_ref(&self) {
+/// self.refcount.replace(self.refcount.get() + 1);
+/// }
+///
+/// unsafe fn dec_ref(this: NonNull<Self>) {
+/// // SAFETY: By requirement on calling this function, the refcount is non-zero,
+/// // implying the underlying object is valid.
+/// let refcount = unsafe { &this.as_ref().refcount };
+/// let new_refcount = refcount.get() - 1;
+/// if new_refcount == 0 {
+/// // The `Foo` will be dropped when `KBox` goes out of scope.
+/// // SAFETY: The [`KBox<Foo>`] is still alive as the old refcount is 1. We can pass
+/// // ownership to the [`KBox`] as by requirement on calling this function,
+/// // the `Self` will no longer be used by the caller.
+/// unsafe { KBox::from_raw(this.as_ptr()) };
+/// } else {
+/// refcount.replace(new_refcount);
+/// }
+/// }
+/// }
+///
+/// impl OwnableRefCounted for Foo {
+/// fn try_from_shared(this: ARef<Self>) -> Result<Owned<Self>, ARef<Self>> {
+/// if this.refcount.get() == 1 {
+/// // SAFETY: The `Foo` is still alive and has no other Rust references as the refcount
+/// // is 1.
+/// Ok(unsafe { Owned::from_raw(ARef::into_raw(this)) })
+/// } else {
+/// Err(this)
+/// }
+/// }
+/// }
+///
+/// impl Ownable for Foo {
+/// unsafe fn release(this: NonNull<Self>) {
+/// // SAFETY: Using `dec_ref()` from [`RefCounted`] to release is okay, as the refcount is
+/// // always 1 for an [`Owned<Foo>`].
+/// unsafe { Foo::dec_ref(this) };
+/// }
+/// }
+///
+/// let foo = Foo::new()?;
+/// let foo = ARef::from(foo);
+/// {
+/// let bar = foo.clone();
+/// assert!(Owned::try_from(bar).is_err());
+/// }
+/// assert!(Owned::try_from(foo).is_ok());
+/// # Ok::<(), Error>(())
+/// ```
+pub trait OwnableRefCounted: RefCounted + Ownable + Sized {
+ /// Checks if the [`ARef`] is unique and converts it to an [`Owned`] if that is the case.
+ /// Otherwise it returns again an [`ARef`] to the same underlying object.
+ fn try_from_shared(this: ARef<Self>) -> Result<Owned<Self>, ARef<Self>>;
+
+ /// Converts the [`Owned`] into an [`ARef`].
+ #[inline]
+ fn into_shared(this: Owned<Self>) -> ARef<Self> {
+ // SAFETY: `Owned::into_raw` returns a pointer to a valid `Self`, and the `Owned` owned the
+ // reference count that we now transfer to the new `ARef`.
+ unsafe { ARef::from_raw(Owned::into_raw(this)) }
+ }
+}
+
+impl<T: OwnableRefCounted> TryFrom<ARef<T>> for Owned<T> {
+ type Error = ARef<T>;
+ /// Tries to convert the [`ARef`] to an [`Owned`] by calling
+ /// [`try_from_shared()`](OwnableRefCounted::try_from_shared). In case the [`ARef`] is not
+ /// unique, it returns again an [`ARef`] to the same underlying object.
+ #[inline]
+ fn try_from(b: ARef<T>) -> Result<Owned<T>, Self::Error> {
+ T::try_from_shared(b)
+ }
+}
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index d0865aeb9371b..77eb390139079 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -23,6 +23,10 @@
ops::Deref,
ptr::NonNull, //
};
+use kernel::types::{
+ OwnableRefCounted,
+ Owned, //
+};
/// Types that are internally reference counted.
///
@@ -35,7 +39,10 @@
/// Note: Implementing this trait allows types to be wrapped in an [`ARef<Self>`]. It requires an
/// internal reference count and provides only shared references. If unique references are required
/// [`Ownable`](crate::types::Ownable) should be implemented which allows types to be wrapped in an
-/// [`Owned<Self>`](crate::types::Owned).
+/// [`Owned<Self>`](crate::types::Owned). Implementing the trait
+/// [`OwnableRefCounted`] allows to convert between unique and
+/// shared references (i.e. [`Owned<Self>`](crate::types::Owned) and
+/// [`ARef<Self>`](crate::types::Owned)).
///
/// # Safety
///
@@ -188,6 +195,13 @@ fn from(b: &T) -> Self {
}
}
+impl<T: OwnableRefCounted> From<Owned<T>> for ARef<T> {
+ #[inline]
+ fn from(b: Owned<T>) -> Self {
+ T::into_shared(b)
+ }
+}
+
impl<T: RefCounted> Drop for ARef<T> {
fn drop(&mut self) {
// SAFETY: The type invariants guarantee that the `ARef` owns the reference we're about to
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 5ef763717e59a..6aa760952cb63 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -18,6 +18,7 @@
pub use crate::{
owned::{
Ownable,
+ OwnableRefCounted,
Owned, //
},
sync::aref::{
--
2.51.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v18 8/8] rust: page: add `from_raw()`
2026-06-25 10:15 [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type Andreas Hindborg
` (6 preceding siblings ...)
2026-06-25 10:15 ` [PATCH v18 7/8] rust: Add `OwnableRefCounted` Andreas Hindborg
@ 2026-06-25 10:15 ` Andreas Hindborg
7 siblings, 0 replies; 12+ messages in thread
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Andreas Hindborg
From: Andreas Hindborg <a.hindborg@samsung.com>
Add a method to `Page` that allows construction of an instance from `struct
page` pointer.
Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Onur Özkan <work@onurozkan.dev>
---
rust/kernel/page.rs | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 6dc1c2395acaf..c88fda09ead5a 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -143,6 +143,20 @@ pub fn nid(&self) -> i32 {
unsafe { bindings::page_to_nid(self.as_ptr()) }
}
+ /// Create a `&Page` from a raw `struct page` pointer.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must be convertible to a shared reference with a lifetime of `'a`.
+ #[inline]
+ pub unsafe fn from_raw<'a>(ptr: *const bindings::page) -> &'a Self {
+ // INVARIANT: By the function safety requirements, `ptr` refers to a valid `struct page`, so
+ // the returned reference upholds the type invariant of `Page`.
+ // SAFETY: By function safety requirements, `ptr` is not null and is convertible to a shared
+ // reference.
+ unsafe { &*ptr.cast() }
+ }
+
/// Runs a piece of code with this page mapped to an address.
///
/// The page is unmapped when this call returns.
--
2.51.2
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