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

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

[Andreas Hindborg]

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@kernel.org>
---
 rust/kernel/block/mq/operations.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs
index 8ad46129a52c..861903e18fbf 100644
--- a/rust/kernel/block/mq/operations.rs
+++ b/rust/kernel/block/mq/operations.rs
@@ -218,7 +218,7 @@ impl<T: Operations> OperationsVTable<T> {
         _set: *mut bindings::blk_mq_tag_set,
         rq: *mut bindings::request,
         _hctx_idx: crate::ffi::c_uint,
-        _numa_node: crate::ffi::c_uint,
+        _numa_node: crate::ffi::c_int,
     ) -> crate::ffi::c_int {
         from_result(|| {
             // SAFETY: By the safety requirements of this function, `rq` points

---
base-commit: 27236c051c01c1c1025e0e0d12a107082557e8f1
change-id: 20260527-block-for-next-2026-05-26-2200-failure-64907085fc49

Best regards,
-- 
Andreas Hindborg <a.hindborg@kernel.org>

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

[Gary Guo]

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@kernel.org>

You could also just use `i32` instead of `ffi::c_int`. But it doesn't really
matter for this patch.

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
>  rust/kernel/block/mq/operations.rs | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

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@garyguo.net> 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@kernel.org>
>
> 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

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

[Gary Guo]

On Wed May 27, 2026 at 11:59 AM BST, Alice Ryhl wrote:
> On Wed, May 27, 2026 at 12:57 PM Gary Guo <gary@garyguo.net> 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@kernel.org>
>>
>> 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.

I wonder if we should actually encourage people, by removing them from prelude,
to use i32/u32 instead of c_int/c_uint, isize/usize instead of c_long/c_ulong
and similar, given all Linux ABIs have consistent mapping for them.

On a different note, perhaps it might worth adding a lint to klint to check for
path references for types available via prelude for other types.

Best,
Gary

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

[mateusz.nowicki]

Hello Andreas,

how can I catch it earlier in the future? I verified patch correctness 
with compiling 'allyesconfig' but
I didn't catch rust issue.

Regards,
Mateusz

On 27.05.2026 11:18, 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@kernel.org>
> ---
>  rust/kernel/block/mq/operations.rs | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/rust/kernel/block/mq/operations.rs
> b/rust/kernel/block/mq/operations.rs
> index 8ad46129a52c..861903e18fbf 100644
> --- a/rust/kernel/block/mq/operations.rs
> +++ b/rust/kernel/block/mq/operations.rs
> @@ -218,7 +218,7 @@ impl<T: Operations> OperationsVTable<T> {
>          _set: *mut bindings::blk_mq_tag_set,
>          rq: *mut bindings::request,
>          _hctx_idx: crate::ffi::c_uint,
> -        _numa_node: crate::ffi::c_uint,
> +        _numa_node: crate::ffi::c_int,
>      ) -> crate::ffi::c_int {
>          from_result(|| {
>              // SAFETY: By the safety requirements of this function, 
> `rq` points
> 
> ---
> base-commit: 27236c051c01c1c1025e0e0d12a107082557e8f1
> change-id: 20260527-block-for-next-2026-05-26-2200-failure-64907085fc49
> 
> Best regards,

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

[Gary Guo]

On Wed May 27, 2026 at 12:57 PM BST, mateusz.nowicki wrote:
> Hello Andreas,
>
> how can I catch it earlier in the future? I verified patch correctness 
> with compiling 'allyesconfig' but
> I didn't catch rust issue.

Currently allyesconfig will skip Rust if you don't have a suitable version of
Rust compiler installed.

There's discussions on getting it changed:
https://lore.kernel.org/rust-for-linux/20260521-evolve-to-crab-v2-1-c18e0e98fc54@chaosmail.tech/

Best,
Gary

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

[Andreas Hindborg]

mateusz.nowicki@posteo.net writes:

> Hello Andreas,
>
> how can I catch it earlier in the future? I verified patch correctness 
> with compiling 'allyesconfig' but
> I didn't catch rust issue.

As Gary says, CONFIG_RUST is silently disabled if the required tools are
not present. Please see the quick start guide for how to get a suitable
compiler on major distros [1].

You can run `make LLVM=1 rustavailable` to check that your tools are set
up correctly.

Best regards,
Andreas Hindborg


[1] https://docs.kernel.org/rust/quick-start.html

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

[Jens Axboe]

On Wed, 27 May 2026 11:18:09 +0200, 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`.
> 
> [...]

Applied, thanks!

[1/1] rust: block: mq: align init_request numa_node arg with C signature
      commit: 6b2f3e4970e48e70c10111366f59f908f2ea6f96

Best regards,
-- 
Jens Axboe