rust: enable `clippy::undocumented_unsafe_blocks` lint

Checking that we are not missing any `// SAFETY` comments in our `unsafe`
blocks is something we have wanted to do for a long time, as well as
cleaning up the remaining cases that were not documented [1].

Back when Rust for Linux started, this was something that could have
been done via a script, like Rust's `tidy`. Soon after, in Rust 1.58.0,
Clippy implemented the `undocumented_unsafe_blocks` lint [2].

Even though the lint has a few false positives, e.g. in some cases where
attributes appear between the comment and the `unsafe` block [3], there
are workarounds and the lint seems quite usable already.

Thus enable the lint now.

We still have a few cases to clean up, so just allow those for the moment
by writing a `TODO` comment -- some of those may be good candidates for
new contributors.

Link: https://github.com/Rust-for-Linux/linux/issues/351 [1]
Link: https://rust-lang.github.io/rust-clippy/master/#/undocumented_unsafe_blocks [2]
Link: https://github.com/rust-lang/rust-clippy/issues/13189 [3]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Tested-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20240904204347.168520-5-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/rust/kernel/list.rs b/rust/kernel/list.rs
index 5b4aec29eb67..fb93330f4af4 100644
--- a/rust/kernel/list.rs
+++ b/rust/kernel/list.rs
@@ -354,6 +354,7 @@ impl<T: ?Sized + ListItem<ID>, const ID: u64> List<T, ID> {
     ///
     /// `item` must not be in a different linked list (with the same id).
     pub unsafe fn remove(&mut self, item: &T) -> Option<ListArc<T, ID>> {
+        // SAFETY: TODO.
         let mut item = unsafe { ListLinks::fields(T::view_links(item)) };
         // SAFETY: The user provided a reference, and reference are never dangling.
         //