[PATCH v2 3/5] rust: maple_tree: add MapleTree::lock() and load()

[Daniel Almeida]

Ah, something else,

[…]

>> +    /// Load the value at the given index.
>> +    ///
>> +    /// # Examples
>> +    ///
>> +    /// Read the value while holding the spinlock.
>> +    ///
>> +    /// ```
>> +    /// use kernel::maple_tree::{MapleTree, InsertErrorKind};
>> +    ///
>> +    /// let tree = KBox::pin_init(MapleTree::<KBox<i32>>::new(), GFP_KERNEL)?;
>> +    ///
>> +    /// let ten = KBox::new(10, GFP_KERNEL)?;
>> +    /// let twenty = KBox::new(20, GFP_KERNEL)?;
>> +    /// tree.insert(100, ten, GFP_KERNEL)?;
>> +    /// tree.insert(200, twenty, GFP_KERNEL)?;
>> +    ///
>> +    /// let mut lock = tree.lock();
>> +    /// assert_eq!(lock.load(100), Some(&mut 10));
>> +    /// assert_eq!(lock.load(200), Some(&mut 20));
>> +    /// assert_eq!(lock.load(300), None);
>> +    /// # Ok::<_, Error>(())
>> +    /// ```
>> +    ///
>> +    /// Increment refcount while holding spinlock and read afterwards.

This sentence can be improved.