linux-kernel - Re: [PATCH -next v7 1/2] rust: clist: Add support to interface with C linked lists

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Message-ID: <5d569c73-6cb6-4d55-8423-c90937049366@nvidia.com>
Date: Mon, 9 Feb 2026 12:02:25 -0500
From: Joel Fernandes <joelagnelf@...dia.com>
To: Daniel Almeida <daniel.almeida@...labora.com>
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Subject: Re: [PATCH -next v7 1/2] rust: clist: Add support to interface with C
 linked lists



On 2/6/2026 5:33 PM, Daniel Almeida wrote:
>>>
>>>
>>> Yeah, but my point being: is there a reason why the underlying list has to
>>> remain read-only? Is this a safety requirement or an invariant that is established
>>> by the code above?
>> I'm not fully sure if it's an invariant or a safety requirement, but anyone
>> creating a C list head on the rust side must guarantee that it is not modified.
>> Since rust has no visibility on the C side, I believe it is a Rust invariant
>> here that the existence of CListHead assumes that the list cannot be modified
>> once Rust has access over it.  That is up to the creator (user) of the CListHead
>> to guarantee. In the DRM buddy case, once the list is allocated and accessible
>> from Rust, C code will not modify it while the Rust object exists.
>>
>> Does that make sense, or is there a better way to document this?
>>
>> --
>> Joel Fernandes
> 
> 
> In which case, I recommend moving this to a safety requirement when
> creating the list.

Ok, will do.
> I assume the purpose of not modifying the list on the C side is to avoid
> corrupting the list in Rust somehow?

Yes.

Thanks,

-- 
Joel Fernandes