Re: [PATCH v2 1/2] io_uring/zcrx: add single shot recvzc

[Jens Axboe <axboe@kernel.dk>]

On 2/21/25 6:06 PM, Pavel Begunkov wrote:
> On 2/22/25 00:52, Jens Axboe wrote:
>>>> @@ -1250,6 +1251,12 @@ int io_recvzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>>        zc->ifq = req->ctx->ifq;
>>>>        if (!zc->ifq)
>>>>            return -EINVAL;
>>>> +    zc->len = READ_ONCE(sqe->len);
>>>> +    if (zc->len == UINT_MAX)
>>>> +        return -EINVAL;
>>>
>>> The uapi gives u32, if we're using a special value it should
>>> match the type. ~(u32)0
>>
>> Any syscall in Linux is capped at 2G anyway, so I think all of this
> 
> I don't see how it related, you don't have to have a weird
> 00111111b as a special value.
> 
>> special meaning of ->len just needs to go away. Just ask for whatever
>> bytes you want, but yes more than 2G will not be supported anyway.
> 
> That's not the case here, the request does support more than 2G,
> it's just spread across multiple CQEs, and the limit accounts
> for multiple CQEs.

All pretty moot if we just go with 0 as the "transfer whatever length
you want", as obviously each individual transfer will be limited anyway.
Which is the better choice than having some odd 4G value.

-- 
Jens Axboe