Re: [PATCH v11 4/4] rust: Add `OwnableRefCounted`

[Andreas Hindborg <a.hindborg@kernel.org>]

"Benno Lossin" <lossin@kernel.org> writes:

> On Tue Jul 8, 2025 at 3:15 PM CEST, Andreas Hindborg wrote:
>> "Benno Lossin" <lossin@kernel.org> writes:
>>> On Mon Jul 7, 2025 at 3:21 PM CEST, Andreas Hindborg wrote:
>>>> When a completion comes back from hardware, it carries the ID. We use
>>>> the C block layer `tag_to_rq` machinery to turn this ID back into an
>>>> `Owned<Request<_>>`. In that process, we check that `refcount == 1` and
>>>> if so, we set refcount to 0 and invent an `Owned<Request<_>>`.
>>>
>>> (because if not, this would be wrong)
>>
>> I hope it is not wrong 😆 You can see the latest and greatest here [1].
>
> Thanks for the pointer, the "implementation details" in the docs on
> `Request` were very helpful! This is another argument for not having the
> blanket impl for `Ownable` when `T: Refcount` I mentioned in the other
> thread.
>
>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/a.hindborg/linux.git/tree/rust/kernel/block/mq/request.rs?h=rnull-v6.15#n398
>
> The comment in line 424 looks wrong?

Yes, nice catch. The assert is correct though.


Best regards,
Andreas Hindborg