1 files changed, 23 insertions, 29 deletions

diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs
index 5246b2c8a4ff..b8fe6be6fcc4 100644
--- a/rust/kernel/rbtree.rs
+++ b/rust/kernel/rbtree.rs
@@ -191,6 +191,12 @@ impl<K, V> RBTree<K, V> {
         }
     }
 
+    /// Returns true if this tree is empty.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.root.rb_node.is_null()
+    }
+
     /// Returns an iterator over the tree nodes, sorted by key.
     pub fn iter(&self) -> Iter<'_, K, V> {
         Iter {
@@ -424,7 +430,7 @@ where
         while !node.is_null() {
             // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self`
             // point to the links field of `Node<K, V>` objects.
-            let this = unsafe { container_of!(node, Node<K, V>, links) }.cast_mut();
+            let this = unsafe { container_of!(node, Node<K, V>, links) };
             // SAFETY: `this` is a non-null node so it is valid by the type invariants.
             let this_key = unsafe { &(*this).key };
             // SAFETY: `node` is a non-null node so it is valid by the type invariants.
@@ -496,7 +502,7 @@ impl<K, V> Drop for RBTree<K, V> {
             // but it is not observable. The loop invariant is still maintained.
 
             // SAFETY: `this` is valid per the loop invariant.
-            unsafe { drop(KBox::from_raw(this.cast_mut())) };
+            unsafe { drop(KBox::from_raw(this)) };
         }
     }
 }
@@ -761,7 +767,7 @@ impl<'a, K, V> Cursor<'a, K, V> {
         let next = self.get_neighbor_raw(Direction::Next);
         // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self`
         // point to the links field of `Node<K, V>` objects.
-        let this = unsafe { container_of!(self.current.as_ptr(), Node<K, V>, links) }.cast_mut();
+        let this = unsafe { container_of!(self.current.as_ptr(), Node<K, V>, links) };
         // SAFETY: `this` is valid by the type invariants as described above.
         let node = unsafe { KBox::from_raw(this) };
         let node = RBTreeNode { node };
@@ -769,23 +775,14 @@ impl<'a, K, V> Cursor<'a, 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.
@@ -806,7 +803,7 @@ impl<'a, K, V> Cursor<'a, K, V> {
             unsafe { bindings::rb_erase(neighbor, addr_of_mut!(self.tree.root)) };
             // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self`
             // point to the links field of `Node<K, V>` objects.
-            let this = unsafe { container_of!(neighbor, Node<K, V>, links) }.cast_mut();
+            let this = unsafe { container_of!(neighbor, Node<K, V>, links) };
             // SAFETY: `this` is valid by the type invariants as described above.
             let node = unsafe { KBox::from_raw(this) };
             return Some(RBTreeNode { node });
@@ -912,7 +909,7 @@ impl<'a, K, V> Cursor<'a, K, V> {
     unsafe fn to_key_value_raw<'b>(node: NonNull<bindings::rb_node>) -> (&'b K, *mut V) {
         // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self`
         // point to the links field of `Node<K, V>` objects.
-        let this = unsafe { container_of!(node.as_ptr(), Node<K, V>, links) }.cast_mut();
+        let this = unsafe { container_of!(node.as_ptr(), Node<K, V>, links) };
         // SAFETY: The passed `node` is the current node or a non-null neighbor,
         // thus `this` is valid by the type invariants.
         let k = unsafe { &(*this).key };
@@ -1021,7 +1018,7 @@ impl<K, V> Iterator for IterRaw<K, V> {
 
         // SAFETY: By the type invariant of `IterRaw`, `self.next` is a valid node in an `RBTree`,
         // and by the type invariant of `RBTree`, all nodes point to the links field of `Node<K, V>` objects.
-        let cur = unsafe { container_of!(self.next, Node<K, V>, links) }.cast_mut();
+        let cur = unsafe { container_of!(self.next, Node<K, V>, links) };
 
         // SAFETY: `self.next` is a valid tree node by the type invariants.
         self.next = unsafe { bindings::rb_next(self.next) };
@@ -1216,7 +1213,7 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
         // SAFETY:
         // - `self.node_links` is a valid pointer to a node in the tree.
         // - We have exclusive access to the underlying tree, and can thus give out a mutable reference.
-        unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links).cast_mut())).value }
+        unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links))).value }
     }
 
     /// Converts the entry into a mutable reference to its value.
@@ -1226,7 +1223,7 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
         // SAFETY:
         // - `self.node_links` is a valid pointer to a node in the tree.
         // - This consumes the `&'a mut RBTree<K, V>`, therefore it can give out a mutable reference that lives for `'a`.
-        unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links).cast_mut())).value }
+        unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links))).value }
     }
 
     /// Remove this entry from the [`RBTree`].
@@ -1239,9 +1236,7 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
         RBTreeNode {
             // SAFETY: The node was a node in the tree, but we removed it, so we can convert it
             // back into a box.
-            node: unsafe {
-                KBox::from_raw(container_of!(self.node_links, Node<K, V>, links).cast_mut())
-            },
+            node: unsafe { KBox::from_raw(container_of!(self.node_links, Node<K, V>, links)) },
         }
     }
 
@@ -1272,8 +1267,7 @@ impl<'a, K, V> OccupiedEntry<'a, K, V> {
         // SAFETY:
         // - `self.node_ptr` produces a valid pointer to a node in the tree.
         // - Now that we removed this entry from the tree, we can convert the node to a box.
-        let old_node =
-            unsafe { KBox::from_raw(container_of!(self.node_links, Node<K, V>, links).cast_mut()) };
+        let old_node = unsafe { KBox::from_raw(container_of!(self.node_links, Node<K, V>, links)) };
 
         RBTreeNode { node: old_node }
     }