Re: [PATCH v3 04/12] rust: xarray: add `XArrayState`

[Andreas Hindborg]

"Tamir Duberstein" <tamird@xxxxxxxxx> writes:

> On Tue, Feb 24, 2026 at 10:43 AM Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
>>
>> "Tamir Duberstein" <tamird@xxxxxxxxx> writes:
>>
>> > On Tue, Feb 24, 2026 at 9:27 AM Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
>> >>
>> >> Tamir Duberstein <tamird@xxxxxxxxx> writes:
>> >>
>> >> > On Mon, Feb 9, 2026 at 6:39 AM Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
>> >> >>
>> >> >> Add `XArrayState` as internal state for XArray iteration and entry
>> >> >> operations. This struct wraps the C `xa_state` structure and holds a
>> >> >> reference to a `Guard` to ensure exclusive access to the XArray for the
>> >> >> lifetime of the state object.
>> >> >>
>> >> >> The `XAS_RESTART` constant is also exposed through the bindings helper
>> >> >> to properly initialize the `xa_node` field.
>> >> >>
>> >> >> The struct and its constructor are marked with `#[expect(dead_code)]` as
>> >> >> there are no users yet. We will remove this annotation in a later patch.
>> >> >>
>> >> >> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
>> >> >> ---
>> >> >>  rust/bindings/bindings_helper.h |  1 +
>> >> >>  rust/kernel/xarray.rs           | 41 ++++++++++++++++++++++++++++++++++++++++-
>> >> >>  2 files changed, 41 insertions(+), 1 deletion(-)
>> >> >>
>> >> >> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
>> >> >> index a067038b4b422..58605c32e8102 100644
>> >> >> --- a/rust/bindings/bindings_helper.h
>> >> >> +++ b/rust/bindings/bindings_helper.h
>> >> >> @@ -117,6 +117,7 @@ const xa_mark_t RUST_CONST_HELPER_XA_PRESENT = XA_PRESENT;
>> >> >>
>> >> >>  const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC = XA_FLAGS_ALLOC;
>> >> >>  const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC1 = XA_FLAGS_ALLOC1;
>> >> >> +const size_t RUST_CONST_HELPER_XAS_RESTART = (size_t)XAS_RESTART;
>> >> >
>> >> > Please add a comment to explain the cast.
>> >>
>> >> How is this:
>> >>
>> >> // `XAS_RESTART` is defined with type `struct xa_node *`. `bindgen`
>> >> // cannot generate pointer typed constants, so we cast to `size_t`.
>> >
>> > Can we include a citation or explain why bindgen can't generate
>> > pointer typed constants?
>>
>> If you have one, I can add it. I don't know why this is the case. My
>> guess is that it's just not implemented yet.
>
> If that's the state of your understanding, that's what the comment
> should say. But IMO the burden of finding out the reason, filing
> appropriate issues upstream, and documenting these things is on you as
> part of this change.

I opened an issue with bindgen [1]. Depending on what they say I will update
the comment.


Best regards,
Andreas Hindborg

[1] https://github.com/rust-lang/rust-bindgen/issues/3347