netdev - Re: IORING_SEND_NOTIF_USER_DATA (was Re: IORING_CQE_F

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Message-ID: <ae88cd67-906a-7c89-eaf8-7ae190c4674b@gmail.com>
Date:   Thu, 20 Oct 2022 16:37:01 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Stefan Metzmacher <metze@...ba.org>,
        io-uring <io-uring@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>
Cc:     Jakub Kicinski <kuba@...nel.org>, netdev <netdev@...r.kernel.org>,
        Dylan Yudaken <dylany@...com>
Subject: Re: IORING_SEND_NOTIF_USER_DATA (was Re: IORING_CQE_F_COPIED)

On 10/20/22 11:10, 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.

Maybe IORING_SETUP_SQE128?

-- 
Pavel Begunkov