[PATCH 05/19] rust: enable `clippy::unnecessary_safety_comment` lint

[Miguel Ojeda]

In Rust 1.67.0, Clippy added the `unnecessary_safety_comment` lint [1],
which is the "inverse" of `undocumented_unsafe_blocks`: it finds places
where safe code has a `// SAFETY` comment attached.

The lint currently finds 3 places where we had such mistakes, thus it
seems already quite useful.

Thus clean those and enable it.

Link: https://rust-lang.github.io/rust-clippy/master/index.html#/unnecessary_safety_comment [1]
Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
---
 Makefile                 | 1 +
 rust/kernel/sync/arc.rs  | 2 +-
 rust/kernel/workqueue.rs | 4 ++--
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index c7a4f313728d..85f37ac9fef8 100644
--- a/Makefile
+++ b/Makefile
@@ -457,6 +457,7 @@ export rust_common_flags := --edition=2021 \
 			    -Wclippy::needless_continue \
 			    -Wclippy::no_mangle_with_rust_abi \
 			    -Wclippy::undocumented_unsafe_blocks \
+			    -Wclippy::unnecessary_safety_comment \
 			    -Wrustdoc::missing_crate_level_docs
 
 KBUILD_HOSTCFLAGS   := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) \
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 3021f30fd822..84c7cbfb096d 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -341,7 +341,7 @@ fn into_foreign(self) -> *const core::ffi::c_void {
     }
 
     unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> ArcBorrow<'a, T> {
-        // SAFETY: By the safety requirement of this function, we know that `ptr` came from
+        // By the safety requirement of this function, we know that `ptr` came from
         // a previous call to `Arc::into_foreign`.
         let inner = NonNull::new(ptr as *mut ArcInner<T>).unwrap();
 
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 3b3f1dbe8192..10d2bc62e2cf 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -526,7 +526,7 @@ unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
     T: HasWork<T, ID>,
 {
     unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
-        // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
+        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
         let ptr = ptr as *mut Work<T, ID>;
         // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
         let ptr = unsafe { T::work_container_of(ptr) };
@@ -573,7 +573,7 @@ unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<Box<T>>
     T: HasWork<T, ID>,
 {
     unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
-        // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
+        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
         let ptr = ptr as *mut Work<T, ID>;
         // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
         let ptr = unsafe { T::work_container_of(ptr) };
-- 
2.46.0