linux-kernel - [PATCH v2] rust: rbtree: simplify finding `current` in `remove

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Message-ID: <20250708075850.25789-1-work@onurozkan.dev>
Date: Tue,  8 Jul 2025 10:58:50 +0300
From: Onur Özkan <work@...rozkan.dev>
To: rust-for-linux@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	lossin@...nel.org,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	dakr@...nel.org,
	mattgilbride@...gle.com,
	wedsonaf@...il.com,
	daniel@...lak.dev,
	tamird@...il.com,
	Onur Özkan <work@...rozkan.dev>
Subject: [PATCH v2] rust: rbtree: simplify finding `current` in `remove_current`

The previous version used a verbose `match` to get
`current`, which may be slightly confusing at first
glance.

This change makes it shorter and more clearly expresses
the intent: prefer `next` if available, otherwise fall
back to `prev`.

Signed-off-by: Onur Özkan <work@...rozkan.dev>
---
 rust/kernel/rbtree.rs | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs
index 8d978c896747..58ad52a07c92 100644
--- a/rust/kernel/rbtree.rs
+++ b/rust/kernel/rbtree.rs
@@ -769,23 +769,14 @@ pub fn remove_current(self) -> (Option<Self>, RBTreeNode<K, V>) {
         // the tree cannot change. By the tree invariant, all nodes are valid.
         unsafe { bindings::rb_erase(&mut (*this).links, addr_of_mut!(self.tree.root)) };

-        let current = match (prev, next) {
-            (_, Some(next)) => next,
-            (Some(prev), None) => prev,
-            (None, None) => {
-                return (None, node);
-            }
-        };
+        // INVARIANT:
+        // - `current` is a valid node in the [`RBTree`] pointed to by `self.tree`.
+        let cursor = next.or(prev).map(|current| Self {
+            current,
+            tree: self.tree,
+        });

-        (
-            // INVARIANT:
-            // - `current` is a valid node in the [`RBTree`] pointed to by `self.tree`.
-            Some(Self {
-                current,
-                tree: self.tree,
-            }),
-            node,
-        )
+        (cursor, node)
     }

     /// Remove the previous node, returning it if it exists.
--
2.50.0