linux-kernel - Re: [PATCH V4 00/17] io_uring/ublk: add IORING_OP_FUSED

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Message-ID: <a786568e-50fb-6f93-352a-1328d0f98a7b@linux.alibaba.com>
Date:   Tue, 28 Mar 2023 11:13:53 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Ming Lei <ming.lei@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-block@...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>,
        Bernd Schubert <bschubert@....com>,
        Pavel Begunkov <asml.silence@...il.com>,
        Stefan Hajnoczi <stefanha@...hat.com>
Subject: Re: [PATCH V4 00/17] io_uring/ublk: add IORING_OP_FUSED_CMD



On 2023/3/28 09:16, Ming Lei wrote:
> Hi Dan,
> 
> On Mon, Mar 27, 2023 at 05:36:33PM -0700, Dan Williams wrote:
>> Ming Lei wrote:
>>> Hello Jens,
>>>
>>> Add IORING_OP_FUSED_CMD, it is one special URING_CMD, which has to
>>> be SQE128. The 1st SQE(master) is one 64byte URING_CMD, and the 2nd
>>> 64byte SQE(slave) is another normal 64byte OP. For any OP which needs
>>> to support slave OP, io_issue_defs[op].fused_slave needs to be set as 1,
>>> and its ->issue() can retrieve/import buffer from master request's
>>> fused_cmd_kbuf. The slave OP is actually submitted from kernel, part of
>>> this idea is from Xiaoguang's ublk ebpf patchset, but this patchset
>>> submits slave OP just like normal OP issued from userspace, that said,
>>> SQE order is kept, and batching handling is done too.
>>
>> Hi Ming,
>>
>> io_uring and ublk are starting to be more on my radar these days. I
>> wanted to take a look at this series, but could not get past the
>> distracting "master"/"slave" terminology in this lead-in paragraph let
>> alone start looking at patches.
>>
>> Frankly, the description sounds more like "head"/"tail", or even
>> "fuse0"/"fuse1" because, for example, who is to say you might not have
> 
> The term "master/slave" is from patches.
> 
> The master command not only provides buffer for slave request, but also requires
> slave request for serving master command, and master command is always completed
> after all slave request are done.
> 
> That is why it is named as master/slave. Actually Jens raised the similar concern
> and I hate the name too, but it is always hard to figure out perfect name, or
> any other name for reflecting the relation? (head/tail, fuse0/1 can't
> do that, IMO)
> 
>> larger fused ops in the future and need terminology to address
>> "fuse{0,1,2,3}"?
> 
> Yeah, definitely, the interface can be extended in future to support
> multiple "slave" requests.

I guess master/slave (especially now) have bad meaning to
English-language guys so it's better to avoid it.

Thanks,
Gao Xiang

> 
> Thanks,
> Ming