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Message-Id: <20241104-borrow-mut-v2-3-de650678648d@gmail.com>
Date: Mon, 04 Nov 2024 17:20:29 -0400
From: Tamir Duberstein <tamird@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
Tamir Duberstein <tamird@...il.com>
Subject: [PATCH v2 3/6] rust: arc: split unsafe block, add missing comment
The new SAFETY comment style is taken from existing comments in `deref`
and `drop.
Signed-off-by: Tamir Duberstein <tamird@...il.com>
---
rust/kernel/sync/arc.rs | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index af383bcd003e1122ebe1b62a49fe40279458e379..9adea755a5ad1a7b03f7fc30a7abc76c1f966c6c 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -377,10 +377,14 @@ fn as_ref(&self) -> &T {
impl<T: ?Sized> Clone for Arc<T> {
fn clone(&self) -> Self {
+ // SAFETY: By the type invariant, there is necessarily a reference to the object, so it is
+ // safe to dereference it.
+ let refcount = unsafe { self.ptr.as_ref() }.refcount.get();
+
// INVARIANT: C `refcount_inc` saturates the refcount, so it cannot overflow to zero.
// SAFETY: By the type invariant, there is necessarily a reference to the object, so it is
// safe to increment the refcount.
- unsafe { bindings::refcount_inc(self.ptr.as_ref().refcount.get()) };
+ unsafe { bindings::refcount_inc(refcount) };
// SAFETY: We just incremented the refcount. This increment is now owned by the new `Arc`.
unsafe { Self::from_inner(self.ptr) }
--
2.47.0
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