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From: mattgilbride@google.com
To: "Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"Andreas Hindborg" <a.hindborg@samsung.com>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Arve Hjønnevåg" <arve@android.com>,
	"Todd Kjos" <tkjos@android.com>,
	"Martijn Coenen" <maco@android.com>,
	"Joel Fernandes" <joel@joelfernandes.org>,
	"Carlos Llamas" <cmllamas@google.com>,
	"Suren Baghdasaryan" <surenb@google.com>,
	"Christian Brauner" <brauner@kernel.org>
Cc: Rob Landley <rob@landley.net>,
	Davidlohr Bueso <dave@stgolabs.net>,
	 Michel Lespinasse <michel@lespinasse.org>,
	rust-for-linux@vger.kernel.org,  linux-kernel@vger.kernel.org,
	Matt Gilbride <mattgilbride@google.com>,
	 Matt Gilbride <mattgilbride@gmail.com>
Subject: [PATCH 4/6] rust: rbtree: add `RBTreeIteratorMut`
Date: Mon, 05 Feb 2024 15:50:04 +0000	[thread overview]
Message-ID: <20240205-b4-rbtree-v1-4-995e3eee38c0@google.com> (raw)
In-Reply-To: <20240205-b4-rbtree-v1-0-995e3eee38c0@google.com>

From: Wedson Almeida Filho <wedsonaf@gmail.com>

Add mutable Iterator implementation (`RBTreeIteratorMut`) 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@google.com/ [1]
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Matt Gilbride <mattgilbride@gmail.com>
---
 rust/kernel/rbtree.rs | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs
index 29d8c2f6bd7b..db17734b3fa1 100644
--- a/rust/kernel/rbtree.rs
+++ b/rust/kernel/rbtree.rs
@@ -221,6 +221,15 @@ pub fn iter(&self) -> RBTreeIterator<'_, K, V> {
         }
     }
 
+    /// Returns a mutable iterator over the tree nodes, sorted by key.
+    pub fn iter_mut(&mut self) -> RBTreeIteratorMut<'_, K, V> {
+        RBTreeIteratorMut {
+            _tree: PhantomData,
+            // SAFETY: `root` is valid as it's embedded in `self` and we have a valid `self`.
+            next: unsafe { bindings::rb_first(&self.root) },
+        }
+    }
+
     /// Returns an iterator over the keys of the nodes in the tree, in sorted order.
     pub fn keys(&self) -> impl Iterator<Item = &'_ K> {
         self.iter().map(|(k, _)| k)
@@ -230,6 +239,11 @@ 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>
@@ -438,6 +452,53 @@ fn next(&mut self) -> Option<Self::Item> {
     }
 }
 
+impl<'a, K, V> IntoIterator for &'a mut RBTree<K, V> {
+    type Item = (&'a K, &'a mut V);
+    type IntoIter = RBTreeIteratorMut<'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 RBTreeIteratorMut<'a, K, V> {
+    _tree: PhantomData<&'a RBTree<K, V>>,
+    next: *mut bindings::rb_node,
+}
+
+// SAFETY: An [`RBTree`] allows the same kinds of access to its values that a struct allows to its
+// fields, so we use the same Send condition as would be used for a struct with K and V fields.
+unsafe impl<'a, K: Send, V: Send> Send for RBTreeIteratorMut<'a, K, V> {}
+
+// SAFETY: An [`RBTree`] allows the same kinds of access to its values that a struct allows to its
+// fields, so we use the same Sync condition as would be used for a struct with K and V fields.
+unsafe impl<'a, K: Sync, V: Sync> Sync for RBTreeIteratorMut<'a, K, V> {}
+
+impl<'a, K, V> Iterator for RBTreeIteratorMut<'a, K, V> {
+    type Item = (&'a K, &'a mut V);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.next.is_null() {
+            return None;
+        }
+
+        // SAFETY: All links fields we create are in a `Node<K, V>`.
+        let cur = unsafe { crate::container_of!(self.next, Node<K, V>, links) }.cast_mut();
+
+        // SAFETY: The reference to the tree used to create the iterator outlives the iterator, so
+        // the tree cannot change (except for the value of previous nodes, but those don't affect
+        // the iteration process). By the tree invariant, all nodes are valid.
+        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, &mut (*cur).value) })
+    }
+}
+
 /// A memory reservation for a red-black tree node.
 ///
 /// It contains the memory needed to hold a node that can be inserted into a red-black tree. One

-- 
2.43.0.594.gd9cf4e227d-goog


  parent reply	other threads:[~2024-02-05 15:50 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-05 15:50 [PATCH 0/6] Red-black tree abstraction needed by Rust Binder mattgilbride
2024-02-05 15:50 ` [PATCH 1/6] rust: add `container_of!` macro mattgilbride
2024-02-09 13:10   ` Alice Ryhl
2024-02-10  8:05   ` Trevor Gross
2024-02-12  9:56     ` Alice Ryhl
2024-02-05 15:50 ` [PATCH 2/6] rust: rbtree: add red-black tree implementation backed by the C version mattgilbride
2024-02-09 13:04   ` Alice Ryhl
2024-02-05 15:50 ` [PATCH 3/6] rust: rbtree: add `RBTreeIterator` mattgilbride
2024-02-09 13:06   ` Alice Ryhl
2024-02-05 15:50 ` mattgilbride [this message]
2024-02-09 13:06   ` [PATCH 4/6] rust: rbtree: add `RBTreeIteratorMut` Alice Ryhl
2024-02-05 15:50 ` [PATCH 5/6] rust: rbtree: add `RBTreeCursor` mattgilbride
2024-02-09 13:06   ` Alice Ryhl
2024-02-05 15:50 ` [PATCH 6/6] rust: rbtree: add `RBTree::entry` mattgilbride
2024-02-09 13:07   ` Alice Ryhl

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