linux-kernel - Re: [PATCH V6 00/17] io_uring/ublk: add generic IORING_OP_FUSED

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Message-ID: <78fe6617-2f5e-3e8e-d853-6dc8ffb5f82c@ddn.com>
Date:   Tue, 18 Apr 2023 19:38:03 +0000
From:   Bernd Schubert <bschubert@....com>
To:     Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        "io-uring@...r.kernel.org" <io-uring@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        ZiyangZhang <ZiyangZhang@...ux.alibaba.com>,
        Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>,
        Pavel Begunkov <asml.silence@...il.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH V6 00/17] io_uring/ublk: add generic IORING_OP_FUSED_CMD

On 3/30/23 13:36, Ming Lei wrote:
[...]
> V6:
> 	- re-design fused command, and make it more generic, moving sharing buffer
> 	as one plugin of fused command, so in future we can implement more plugins
> 	- document potential other use cases of fused command
> 	- drop support for builtin secondary sqe in SQE128, so all secondary
> 	  requests has standalone SQE
> 	- make fused command as one feature
> 	- cleanup & improve naming

Hi Ming, et al.,

I started to wonder if fused SQE could be extended to combine multiple 
syscalls, for example open/read/close.  Which would be another solution 
for the readfile syscall Miklos had proposed some time ago.

https://lore.kernel.org/lkml/CAJfpegusi8BjWFzEi05926d4RsEQvPnRW-w7My=ibBHQ8NgCuw@mail.gmail.com/

If fused SQEs could be extended, I think it would be quite helpful for 
many other patterns. Another similar examples would open/write/close, 
but ideal would be also to allow to have it more complex like 
"open/write/sync_file_range/close" - open/write/close might be the 
fastest and could possibly return before sync_file_range. Use case for 
the latter would be a file server that wants to give notifications to 
client when pages have been written out.

Thanks,
Bernd