From 96fff2dc2954dcaf7affe7da212aba3f5107d06d Mon Sep 17 00:00:00 2001 From: Kartik Prajapati Date: Wed, 21 Aug 2024 19:58:58 +0000 Subject: 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 Co-developed-by: Alice Ryhl Signed-off-by: Alice Ryhl Reviewed-by: Benno Lossin [ Reworded to correct the author reference and changed tag to Link since it is not a bug. - Miguel ] Signed-off-by: Miguel Ojeda --- 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 ee7dd1f963ef..9e7ca066355c 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 ARef { _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) {} + /// } + /// + /// let mut data = Empty {}; + /// let ptr = NonNull::::new(&mut data as *mut _).unwrap(); + /// let data_ref: ARef = unsafe { ARef::from_raw(ptr) }; + /// let raw_ptr: NonNull = ARef::into_raw(data_ref); + /// + /// assert_eq!(ptr, raw_ptr); + /// ``` + pub fn into_raw(me: Self) -> NonNull { + ManuallyDrop::new(me).ptr + } } impl Clone for ARef { -- cgit v1.2.3-58-ga151