Re: [PATCH V4 00/17] io_uring/ublk: add IORING_OP_FUSED_CMD

From: Jens Axboe <axboe@kernel.dk>
To: Ming Lei <ming.lei@redhat.com>, Dan Williams <dan.j.williams@intel.com>
Cc: io-uring@vger.kernel.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Miklos Szeredi <mszeredi@redhat.com>,
	ZiyangZhang <ZiyangZhang@linux.alibaba.com>,
	Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>,
	Bernd Schubert <bschubert@ddn.com>,
	Pavel Begunkov <asml.silence@gmail.com>,
	Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [PATCH V4 00/17] io_uring/ublk: add IORING_OP_FUSED_CMD
Date: Mon, 27 Mar 2023 19:29:36 -0600	[thread overview]
Message-ID: <11651593-79d3-b21a-6441-63e1de5b39aa@kernel.dk> (raw)
In-Reply-To: <ZCJABlFshb0UmTMv@ovpn-8-20.pek2.redhat.com>

On 3/27/23 7:16 PM, 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)

Indeed. What about primary/secondary? And it'd be quite possible to have
multiple secondaries too.

-- 
Jens Axboe