Re: linux-next: build failure after merge of the rust-pin-init tree

["Benno Lossin" <lossin@kernel.org>]

On Tue Jun 10, 2025 at 11:32 AM CEST, Andreas Hindborg wrote:
> "Benno Lossin" <lossin@kernel.org> writes:
>
>> On Tue Jun 10, 2025 at 9:59 AM CEST, Benno Lossin wrote:
>>> On Tue Jun 10, 2025 at 6:22 AM CEST, Stephen Rothwell wrote:
>>>> Hi all,
>>>>
>>>> After merging the rust-pin-init tree, today's linux-next build (x86_64
>>>> allmodconfig) failed like this:
>>>>
>>>> error[E0282]: type annotations needed
>>>>    --> rust/kernel/configfs.rs:154:26
>>>>     |
>>>> 154 |             subsystem <- pin_init::zeroed().chain(
>>>>     |                          ^^^^^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `zeroed`
>>>>     |
>>>> help: consider specifying the generic argument
>>>>     |
>>>> 154 |             subsystem <- pin_init::zeroed::<T>().chain(
>>>>     |                                          +++++
>>>>
>>>> error[E0282]: type annotations needed
>>>>    --> rust/kernel/configfs.rs:264:22
>>>>     |
>>>> 264 |             group <- pin_init::zeroed().chain(|v: &mut Opaque<bindings::config_group>| {
>>>>     |                      ^^^^^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `zeroed`
>>>>     |
>>>> help: consider specifying the generic argument
>>>>     |
>>>> 264 |             group <- pin_init::zeroed::<T>().chain(|v: &mut Opaque<bindings::config_group>| {
>>>>     |                                      +++++
>>>>
>>>> error: aborting due to 2 previous errors
>>>>
>>>> For more information about this error, try `rustc --explain E0282`.
>>>>
>>>> Caused by commit
>>>>
>>>>   0bcaea04244b ("rust: pin-init: rename `zeroed` to `init_zeroed`")
>>>>
>>>> I have used the rust-pin-init tree from next-20250606 for today.
>>>
>>> Thanks for catching this! I didn't test with `CONFIG_CONFIGFS=y`, so the
>>> code was cfg'd out... I'll add it to my tests.
>>>
>>> @Andreas I'll send a new version of the commit above with configfs
>>> changed.
>>
>> (sorry forgot to add your emails and also some new info)
>>
>> Actually, the correct change would be this in commit 0bcaea04244b
>> ("rust: pin-init: rename `zeroed` to `init_zeroed`"):
>>
>> diff --git a/rust/kernel/configfs.rs b/rust/kernel/configfs.rs
>> index 34d0bea4f9a5..6d566a8bde74 100644
>> --- a/rust/kernel/configfs.rs
>> +++ b/rust/kernel/configfs.rs
>> @@ -151,7 +151,7 @@ pub fn new(
>>          data: impl PinInit<Data, Error>,
>>      ) -> impl PinInit<Self, Error> {
>>          try_pin_init!(Self {
>> -            subsystem <- pin_init::zeroed().chain(
>> +            subsystem <- pin_init::init_zeroed().chain(
>>                  |place: &mut Opaque<bindings::configfs_subsystem>| {
>>                      // SAFETY: We initialized the required fields of `place.group` above.
>>                      unsafe {
>> @@ -261,7 +261,7 @@ pub fn new(
>>          data: impl PinInit<Data, Error>,
>>      ) -> impl PinInit<Self, Error> {
>>          try_pin_init!(Self {
>> -            group <- pin_init::zeroed().chain(|v: &mut Opaque<bindings::config_group>| {
>> +            group <- pin_init::init_zeroed().chain(|v: &mut Opaque<bindings::config_group>| {
>>                  let place = v.get();
>>                  let name = name.as_bytes_with_nul().as_ptr();
>>                  // SAFETY: It is safe to initialize a group once it has been zeroed.
>>
>> @Miguel, @Andreas, how should I go about this? Send the commit above
>> augmented with the diff, or send a patch with just the diff to the list?
>> Or apply the diff directly to the commit in the pin-init-next branch &
>> rebasing (potentially adding an Acked-by from Andreas)? Or some other
>> way?
>
> I think you should add this change directly in your tree. I think you
> should just fold it into the breaking commit so we avoid commits that do
> not build.
>
> Acked-by: Andreas Hindborg <a.hindborg@kernel.org>

Thanks and done!

---
Cheers,
Benno