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

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Message-ID: <ZCJERSOkzIo+SIm7@ovpn-8-20.pek2.redhat.com>
Date:   Tue, 28 Mar 2023 09:35:01 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Dan Williams <dan.j.williams@...el.com>, 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>, ming.lei@...hat.com
Subject: Re: [PATCH V4 00/17] io_uring/ublk: add IORING_OP_FUSED_CMD

On Mon, Mar 27, 2023 at 07:29:36PM -0600, Jens Axboe wrote:
> 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.

OK, I will take primary/secondary in V5 if no better name is suggested.


Thanks,
Ming