Re: [RFC PATCHv2 1/1] io_uring: add support for IORING_SETUP_SQE_MIXED

[Jens Axboe <axboe@kernel.dk>]

On 9/11/25 7:07 AM, Ming Lei wrote:
> On Thu, Sep 11, 2025 at 9:02?PM Keith Busch <kbusch@kernel.org> wrote:
>>
>> On Thu, Sep 11, 2025 at 10:19:06AM +0800, Ming Lei wrote:
>>> On Thu, Sep 11, 2025 at 10:11:47AM +0800, Ming Lei wrote:
>>>> SQE128 is used for uring_cmd only, so it could be one uring_cmd
>>>> private flag. However, the implementation may be ugly and fragile.
>>>
>>> Or in case of IORING_SETUP_SQE_MIXED, IORING_OP_URING_CMD is always interpreted
>>> as plain 64bit SQE, also add IORING_OP_URING_CMD128 for SQE128 only.
>>
>> Maybe that's good enough, but I was looking for more flexibility to have
>> big SQEs for read/write too. Not that I have a strong use case for it
>> now, but in hindsight, that's where "io_uring_attr_pi" should have been
>> placed instead of outide the submission queue.
> 
> Then you can add READ128/WRITE128...

Yeah, I do think this is the best approach - make it implied by the
opcode. Doesn't mean we have to bifurcate the whole opcode space,
as generally not a lot of opcodes will want/need an 128b SQE.

And it also nicely solves the issue of needing to solve the flags space
issue.

So maybe spin a v3 with that approach?

-- 
Jens Axboe