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

[Alice Ryhl <aliceryhl@google.com>]

On Sat, Jul 26, 2025 at 5:54 PM Gary Guo <gary@garyguo.net> wrote:
>
> On Sat, 26 Jul 2025 13:23:24 +0000
> Alice Ryhl <aliceryhl@google.com> 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@google.com>
> > ---
> >  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`?

They differ on whether the error code is EBUSY or EEXIST.

Alice