Re: [PATCH 3/3] rust: maple_tree: add MapleTreeAlloc

[Gary Guo]

On Sat, 26 Jul 2025 13:23:24 +0000
Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote:

> To support allocation trees, we introduce a new type MapleTreeAlloc for
> the case where the tree is created using MT_FLAGS_ALLOC_RANGE. To ensure
> that you can only call mtree_alloc_range on an allocation tree, we
> restrict thta method to the new MapleTreeAlloc type. However, all
> methods on MapleTree remain accessible to MapleTreeAlloc as allocation
> trees can use the other methods without issues.
> 
> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> ---
>  rust/kernel/maple_tree.rs | 158 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 158 insertions(+)
> 
> diff --git a/rust/kernel/maple_tree.rs b/rust/kernel/maple_tree.rs
> index c7ef504a9c78065b3d5752b4f5337fb6277182d1..8c025d2c395b6d57f1fb16214b4e87d4e7942d6f 100644
> --- a/rust/kernel/maple_tree.rs
> +++ b/rust/kernel/maple_tree.rs
>
>  /// Error type for failure to insert a new value.
>  pub struct InsertError<T> {
>      /// The value that could not be inserted.
> @@ -378,3 +499,40 @@ fn from(insert_err: InsertError<T>) -> Error {
>          Error::from(insert_err.cause)
>      }
>  }
> +
> +/// Error type for failure to insert a new value.
> +pub struct AllocError<T> {
> +    /// The value that could not be inserted.
> +    pub value: T,
> +    /// The reason for the failure to insert.
> +    pub cause: AllocErrorKind,
> +}
> +
> +/// The reason for the failure to insert.
> +#[derive(PartialEq, Eq, Copy, Clone)]
> +pub enum AllocErrorKind {
> +    /// There is not enough space for the requested allocation.
> +    Busy,
> +    /// Failure to allocate memory.
> +    Nomem,
> +    /// The insertion request was invalid.
> +    InvalidRequest,
> +}
> +
> +impl From<AllocErrorKind> for Error {
> +    #[inline]
> +    fn from(kind: AllocErrorKind) -> Error {
> +        match kind {
> +            AllocErrorKind::Busy => EBUSY,
> +            AllocErrorKind::Nomem => ENOMEM,
> +            AllocErrorKind::InvalidRequest => EINVAL,
> +        }
> +    }
> +}
> +
> +impl<T> From<AllocError<T>> for Error {
> +    #[inline]
> +    fn from(insert_err: AllocError<T>) -> Error {
> +        Error::from(insert_err.cause)
> +    }
> +}
> 

This looks identical to `InsertError`?

Best,
Gary