[PATCH v4 3/6] rust: arc: split unsafe block, add missing comment
From: Tamir Duberstein
Date: Sun Nov 10 2024 - 09:15:02 EST
The new SAFETY comment style is taken from existing comments in `deref`
and `drop.
Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxx>
---
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 bbb6ca8ff7d0e079c7f0efa7702a91622759cbd7..6f5fe24f0e1bad5ca141091e8945b8d2f94e16aa 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