From 96fff2dc2954dcaf7affe7da212aba3f5107d06d Mon Sep 17 00:00:00 2001
From: Kartik Prajapati <kartikprajapati987@gmail.com>
Date: Wed, 21 Aug 2024 19:58:58 +0000
Subject: [PATCH] rust: types: add `ARef::into_raw`
Add a method for `ARef` that is analogous to `Arc::into_raw`. It is the
inverse operation of `ARef::from_raw`, and allows you to convert the
`ARef` back into a raw pointer while retaining ownership of the
refcount.
This new function will be used by [1] for converting the type in an
`ARef` using `ARef::from_raw(ARef::into_raw(me).cast())`. Alice has
also needed the same function for other use-cases in the past, but [1]
is the first to go upstream.
This was implemented independently by Kartik and Alice. The two versions
were merged by Alice, so all mistakes are Alice's.
Link: https://lore.kernel.org/r/20240801-vma-v3-1-db6c1c0afda9@google.com [1]
Link: https://github.com/Rust-for-Linux/linux/issues/1044
Signed-off-by: Kartik Prajapati <kartikprajapati987@gmail.com>
Co-developed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
[ Reworded to correct the author reference and changed tag to Link
since it is not a bug. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
rust/kernel/types.rs | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index ee7dd1f963efc..9e7ca066355cd 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -7,7 +7,7 @@ use alloc::boxed::Box;
use core::{
cell::UnsafeCell,
marker::{PhantomData, PhantomPinned},
- mem::MaybeUninit,
+ mem::{ManuallyDrop, MaybeUninit},
ops::{Deref, DerefMut},
pin::Pin,
ptr::NonNull,
@@ -396,6 +396,35 @@ impl<T: AlwaysRefCounted> ARef<T> {
_p: PhantomData,
}
}
+
+ /// Consumes the `ARef`, returning a raw pointer.
+ ///
+ /// This function does not change the refcount. After calling this function, the caller is
+ /// responsible for the refcount previously managed by the `ARef`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use core::ptr::NonNull;
+ /// use kernel::types::{ARef, AlwaysRefCounted};
+ ///
+ /// struct Empty {}
+ ///
+ /// unsafe impl AlwaysRefCounted for Empty {
+ /// fn inc_ref(&self) {}
+ /// unsafe fn dec_ref(_obj: NonNull<Self>) {}
+ /// }
+ ///
+ /// let mut data = Empty {};
+ /// let ptr = NonNull::<Empty>::new(&mut data as *mut _).unwrap();
+ /// let data_ref: ARef<Empty> = unsafe { ARef::from_raw(ptr) };
+ /// let raw_ptr: NonNull<Empty> = ARef::into_raw(data_ref);
+ ///
+ /// assert_eq!(ptr, raw_ptr);
+ /// ```
+ pub fn into_raw(me: Self) -> NonNull<T> {
+ ManuallyDrop::new(me).ptr
+ }
}
impl<T: AlwaysRefCounted> Clone for ARef<T> {
--
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