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From: Tamir Duberstein <tamird@gmail.com>
To: "Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Andreas Hindborg" <a.hindborg@kernel.org>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Danilo Krummrich" <dakr@kernel.org>
Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
	 Tamir Duberstein <tamird@gmail.com>
Subject: [PATCH 4/5] rust: reorder `ForeignOwnable` items
Date: Wed, 30 Oct 2024 16:46:41 -0400	[thread overview]
Message-ID: <20241030-borrow-mut-v1-4-8f0ceaf78eaf@gmail.com> (raw)
In-Reply-To: <20241030-borrow-mut-v1-0-8f0ceaf78eaf@gmail.com>

`{into,from}_foreign` before `borrow` is slightly more logical.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/sync/arc.rs | 18 +++++++++---------
 rust/kernel/types.rs    | 20 ++++++++++----------
 2 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 26b7272424aafdd4847d9642456cab837797ac33..4552913c75f747d646bf408c1e8a1a883afb4b6a 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -339,29 +339,29 @@ fn into_foreign(self) -> *mut core::ffi::c_void {
         ManuallyDrop::new(self).ptr.as_ptr().cast()
     }
 
-    unsafe fn borrow<'a>(ptr: *mut core::ffi::c_void) -> ArcBorrow<'a, T> {
+    unsafe fn from_foreign(ptr: *mut core::ffi::c_void) -> Self {
         let ptr = ptr.cast();
 
         // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous
         // call to `Self::into_foreign`.
         let inner = unsafe { NonNull::new_unchecked(ptr) };
 
-        // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive
-        // for the lifetime of the returned value.
-        unsafe { ArcBorrow::new(inner) }
+        // SAFETY: By the safety requirement of this function, we know that `ptr` came from
+        // a previous call to `Arc::into_foreign`, which guarantees that `ptr` is valid and
+        // holds a reference count increment that is transferrable to us.
+        unsafe { Self::from_inner(inner) }
     }
 
-    unsafe fn from_foreign(ptr: *mut core::ffi::c_void) -> Self {
+    unsafe fn borrow<'a>(ptr: *mut core::ffi::c_void) -> ArcBorrow<'a, T> {
         let ptr = ptr.cast();
 
         // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous
         // call to `Self::into_foreign`.
         let inner = unsafe { NonNull::new_unchecked(ptr) };
 
-        // SAFETY: By the safety requirement of this function, we know that `ptr` came from
-        // a previous call to `Arc::into_foreign`, which guarantees that `ptr` is valid and
-        // holds a reference count increment that is transferrable to us.
-        unsafe { Self::from_inner(inner) }
+        // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive
+        // for the lifetime of the returned value.
+        unsafe { ArcBorrow::new(inner) }
     }
 }
 
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 04358375794dc5ba7bfebbe3cfc5885cff531f15..b8a7b2ee96a17081ad31e1bb73cb0513bcd05ef4 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -31,14 +31,6 @@ pub trait ForeignOwnable: Sized {
     /// [`ForeignOwnable::try_from_foreign`] can result in undefined behavior.
     fn into_foreign(self) -> *mut core::ffi::c_void;
 
-    /// Borrows a foreign-owned object.
-    ///
-    /// # Safety
-    ///
-    /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for
-    /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet.
-    unsafe fn borrow<'a>(ptr: *mut core::ffi::c_void) -> Self::Borrowed<'a>;
-
     /// Converts a foreign-owned object back to a Rust-owned one.
     ///
     /// # Safety
@@ -67,6 +59,14 @@ unsafe fn try_from_foreign(ptr: *mut core::ffi::c_void) -> Option<Self> {
             unsafe { Some(Self::from_foreign(ptr)) }
         }
     }
+
+    /// Borrows a foreign-owned object.
+    ///
+    /// # Safety
+    ///
+    /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for
+    /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet.
+    unsafe fn borrow<'a>(ptr: *mut core::ffi::c_void) -> Self::Borrowed<'a>;
 }
 
 impl ForeignOwnable for () {
@@ -76,9 +76,9 @@ fn into_foreign(self) -> *mut core::ffi::c_void {
         core::ptr::NonNull::dangling().as_ptr()
     }
 
-    unsafe fn borrow<'a>(_: *mut core::ffi::c_void) -> Self::Borrowed<'a> {}
-
     unsafe fn from_foreign(_: *mut core::ffi::c_void) -> Self {}
+
+    unsafe fn borrow<'a>(_: *mut core::ffi::c_void) -> Self::Borrowed<'a> {}
 }
 
 /// Runs a cleanup function/closure when dropped.

-- 
2.47.0


  parent reply	other threads:[~2024-10-30 20:46 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-30 20:46 [PATCH 0/5] rust: add improved version of `ForeignOwnable::borrow_mut` Tamir Duberstein
2024-10-30 20:46 ` [PATCH 1/5] rust: arc: use `NonNull::new_unchecked` Tamir Duberstein
2024-10-31  8:27   ` Andreas Hindborg
2024-10-31 11:50     ` Tamir Duberstein
2024-10-31  8:37   ` Alice Ryhl
2024-10-30 20:46 ` [PATCH 2/5] rust: types: avoid `as` casts, narrow unsafe scope Tamir Duberstein
2024-10-31  8:41   ` Andreas Hindborg
2024-10-31 11:50     ` Tamir Duberstein
2024-11-01 13:21       ` Andreas Hindborg
2024-11-04 21:19         ` Tamir Duberstein
2024-10-31  8:46   ` Alice Ryhl
2024-10-31 13:24     ` Tamir Duberstein
2024-10-30 20:46 ` [PATCH 3/5] rust: change `ForeignOwnable` pointer to mut Tamir Duberstein
2024-10-31  8:45   ` Andreas Hindborg
2024-10-31  8:53   ` Alice Ryhl
2024-10-30 20:46 ` Tamir Duberstein [this message]
2024-10-31  8:46   ` [PATCH 4/5] rust: reorder `ForeignOwnable` items Andreas Hindborg
2024-10-31 12:22     ` Tamir Duberstein
2024-10-31 12:40       ` Miguel Ojeda
2024-10-31 13:30         ` Tamir Duberstein
2024-11-01 13:24           ` Andreas Hindborg
2024-11-01 13:22         ` Andreas Hindborg
2024-10-30 20:46 ` [PATCH 5/5] rust: add improved version of `ForeignOwnable::borrow_mut` Tamir Duberstein
2024-10-31  8:50   ` Andreas Hindborg
2024-10-31 10:54   ` Alice Ryhl
2024-10-31 12:23     ` Tamir Duberstein
2024-10-31 12:27       ` Miguel Ojeda

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