Re: IORING_SEND_NOTIF_USER_DATA (was Re: IORING_CQE_F_COPIED)

From: Pavel Begunkov <asml.silence@gmail.com>
To: Stefan Metzmacher <metze@samba.org>,
	io-uring <io-uring@vger.kernel.org>, Jens Axboe <axboe@kernel.dk>
Cc: Jakub Kicinski <kuba@kernel.org>, netdev <netdev@vger.kernel.org>,
	Dylan Yudaken <dylany@fb.com>
Subject: Re: IORING_SEND_NOTIF_USER_DATA (was Re: IORING_CQE_F_COPIED)
Date: Fri, 21 Oct 2022 10:27:29 +0100	[thread overview]
Message-ID: <fc3967d3-ef72-7940-2436-3d8aa329151e@gmail.com> (raw)
In-Reply-To: <86763cf2-72ed-2d05-99c3-237ce4905611@samba.org>

On 10/21/22 09:32, Stefan Metzmacher wrote:
> Hi Pavel,
> 
>>>>> Experimenting with this stuff lets me wish to have a way to
>>>>> have a different 'user_data' field for the notif cqe,
>>>>> maybe based on a IORING_RECVSEND_ flag, it may make my life
>>>>> easier and would avoid some complexity in userspace...
>>>>> As I need to handle retry on short writes even with MSG_WAITALL
>>>>> as EINTR and other errors could cause them.
>>>>>
>>>>> What do you think?
>>>
>>> Any comment on this?
>>>
>>> IORING_SEND_NOTIF_USER_DATA could let us use
>>> notif->cqe.user_data = sqe->addr3;
>>
>> I'd rather not use the last available u64, tbh, that was the
>> reason for not adding a second user_data in the first place.
> 
> As far as I can see io_send_zc_prep has this:
> 
>          if (unlikely(READ_ONCE(sqe->__pad2[0]) || READ_ONCE(sqe->addr3)))
>                  return -EINVAL;
> 
> both are u64...

Hah, true, completely forgot about that one

-- 
Pavel Begunkov