[PATCH v4 4/6] rust: rbtree: add mutable iterator
From: Matt Gilbride
Date: Mon Jun 03 2024 - 12:06:41 EST
From: Wedson Almeida Filho <wedsonaf@xxxxxxxxx>
Add mutable Iterator implementation for `RBTree`,
allowing iteration over (key, value) pairs in key order. Only values are
mutable, as mutating keys implies modifying a node's position in the tree.
Mutable iteration is used by the binder driver during shutdown to
clean up the tree maintained by the "range allocator" [1].
Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-6-08ba9197f637@xxxxxxxxxx/ [1]
Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxx>
Signed-off-by: Matt Gilbride <mattgilbride@xxxxxxxxxx>
Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
Tested-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
---
rust/kernel/rbtree.rs | 98 ++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 86 insertions(+), 12 deletions(-)
diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs
index 6ebea833e5a9..28dfa36e81c3 100644
--- a/rust/kernel/rbtree.rs
+++ b/rust/kernel/rbtree.rs
@@ -197,8 +197,26 @@ pub fn iter(&self) -> Iter<'_, K, V> {
// INVARIANT: `bindings::rb_first` returns a valid pointer to a tree node given a valid pointer to a tree root.
Iter {
_tree: PhantomData,
- // SAFETY: `self.root` is a valid pointer to the tree root.
- next: unsafe { bindings::rb_first(&self.root) },
+ iter_raw: IterRaw {
+ // SAFETY: by the invariants, all pointers are valid.
+ next: unsafe { bindings::rb_first(&self.root) },
+ _phantom: PhantomData,
+ },
+ }
+ }
+
+ /// Returns a mutable iterator over the tree nodes, sorted by key.
+ pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
+ IterMut {
+ _tree: PhantomData,
+ // INVARIANT:
+ // - `self.root` is a valid pointer to a tree root.
+ // - `bindings::rb_first` produces a valid pointer to a node given `root` is valid.
+ iter_raw: IterRaw {
+ // SAFETY: by the invariants, all pointers are valid.
+ next: unsafe { bindings::rb_first(&self.root) },
+ _phantom: PhantomData,
+ },
}
}
@@ -211,6 +229,11 @@ pub fn keys(&self) -> impl Iterator<Item = &'_ K> {
pub fn values(&self) -> impl Iterator<Item = &'_ V> {
self.iter().map(|(_, v)| v)
}
+
+ /// Returns a mutable iterator over the values of the nodes in the tree, sorted by key.
+ pub fn values_mut(&mut self) -> impl Iterator<Item = &'_ mut V> {
+ self.iter_mut().map(|(_, v)| v)
+ }
}
impl<K, V> RBTree<K, V>
@@ -414,13 +437,9 @@ fn into_iter(self) -> Self::IntoIter {
/// An iterator over the nodes of a [`RBTree`].
///
/// Instances are created by calling [`RBTree::iter`].
-///
-/// # Invariants
-/// - `self.next` is a valid pointer.
-/// - `self.next` points to a node stored inside of a valid `RBTree`.
pub struct Iter<'a, K, V> {
_tree: PhantomData<&'a RBTree<K, V>>,
- next: *mut bindings::rb_node,
+ iter_raw: IterRaw<K, V>,
}
// SAFETY: The [`Iter`] gives out immutable references to K and V, so it has the same
@@ -434,21 +453,76 @@ unsafe impl<'a, K: Sync, V: Sync> Sync for Iter<'a, K, V> {}
impl<'a, K, V> Iterator for Iter<'a, K, V> {
type Item = (&'a K, &'a V);
+ fn next(&mut self) -> Option<Self::Item> {
+ self.iter_raw.next().map(|(k, v)|
+ // SAFETY: Due to `self._tree`, `k` and `v` are valid for the lifetime of `'a`.
+ unsafe { (&*k, &*v) })
+ }
+}
+
+impl<'a, K, V> IntoIterator for &'a mut RBTree<K, V> {
+ type Item = (&'a K, &'a mut V);
+ type IntoIter = IterMut<'a, K, V>;
+
+ fn into_iter(self) -> Self::IntoIter {
+ self.iter_mut()
+ }
+}
+
+/// A mutable iterator over the nodes of a [`RBTree`].
+///
+/// Instances are created by calling [`RBTree::iter_mut`].
+pub struct IterMut<'a, K, V> {
+ _tree: PhantomData<&'a mut RBTree<K, V>>,
+ iter_raw: IterRaw<K, V>,
+}
+
+// SAFETY: The [`RBTreeIterator`] gives out mutable references to K and V, so it has the same
+// thread safety requirements as mutable references.
+unsafe impl<'a, K: Send, V: Send> Send for IterMut<'a, K, V> {}
+
+// SAFETY: The [`RBTreeIterator`] gives out mutable references to K and V, so it has the same
+// thread safety requirements as mutable references.
+unsafe impl<'a, K: Sync, V: Sync> Sync for IterMut<'a, K, V> {}
+
+impl<'a, K, V> Iterator for IterMut<'a, K, V> {
+ type Item = (&'a K, &'a mut V);
+
+ fn next(&mut self) -> Option<Self::Item> {
+ self.iter_raw.next().map(|(k, v)|
+ // SAFETY: Due to `&mut self`, we have exclusive access to `k` and `v`, for the lifetime of `'a`.
+ unsafe { (&*k, &mut *v) })
+ }
+}
+
+/// A raw iterator over the nodes of a [`RBTree`].
+///
+/// # Invariants
+/// - `self.next` is a valid pointer.
+/// - `self.next` points to a node stored inside of a valid `RBTree`.
+struct IterRaw<K, V> {
+ next: *mut bindings::rb_node,
+ _phantom: PhantomData<fn() -> (K, V)>,
+}
+
+impl<K, V> Iterator for IterRaw<K, V> {
+ type Item = (*mut K, *mut V);
+
fn next(&mut self) -> Option<Self::Item> {
if self.next.is_null() {
return None;
}
- // SAFETY: By the type invariant of `Iter`, `self.next` is a valid node in an `RBTree`,
+ // 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) };
+ let cur: *mut Node<K, V> =
+ unsafe { container_of!(self.next, Node<K, V>, links) }.cast_mut();
// SAFETY: `self.next` is a valid tree node by the type invariants.
self.next = unsafe { bindings::rb_next(self.next) };
- // SAFETY: By the same reasoning above, it is safe to dereference the node. Additionally,
- // it is ok to return a reference to members because the iterator must outlive it.
- Some(unsafe { (&(*cur).key, &(*cur).value) })
+ // SAFETY: By the same reasoning above, it is safe to dereference the node.
+ Some(unsafe { (addr_of_mut!((*cur).key), addr_of_mut!((*cur).value)) })
}
}
--
2.45.1.288.g0e0cd299f1-goog