Re: [PATCH] rust: block: mq: align init_request numa_node arg with C signature

[Alice Ryhl]

On Wed, May 27, 2026 at 12:57 PM Gary Guo <gary@xxxxxxxxxxx> wrote:
>
> On Wed May 27, 2026 at 10:18 AM BST, Andreas Hindborg wrote:
> > Commit b040a1a4523d ("block: switch numa_node to int in
> > blk_mq_hw_ctx and init_request") changed the type of the
> > `numa_node` argument of `blk_mq_ops::init_request` from
> > `unsigned int` to `int`. Update the Rust callback signature to
> > match, so that the function item can be coerced to the C fn
> > pointer type stored in `blk_mq_ops`.
> >
> > Without this change the Rust block layer fails to build:
> >
> >   error[E0308]: mismatched types
> >      --> rust/kernel/block/mq/operations.rs:274:28
> >       |
> >   274 |         init_request: Some(Self::init_request_callback),
> >       |                       ---- ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >       |                       expected fn pointer, found fn item
> >       |
> >       = note: expected fn pointer
> >                 `unsafe extern "C" fn(_, _, _, i32) -> _`
> >                     found fn item
> >                 `unsafe extern "C" fn(_, _, _, u32) -> _ {...}`
> >
> > The argument is unused on the Rust side, so this is a pure
> > type-signature change with no functional impact.
> >
> > Fixes: b040a1a4523d ("block: switch numa_node to int in blk_mq_hw_ctx and init_request")
> > Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
>
> You could also just use `i32` instead of `ffi::c_int`. But it doesn't really
> matter for this patch.

By the way, all these constants are in the prelude.

Alice