linux-kernel - Re: [PATCH 1/2] io_uring: Pass whole sqe to commands

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Date:   Thu, 20 Apr 2023 14:31:39 +0200
From:   Christoph Hellwig <hch@....de>
To:     Breno Leitao <leitao@...ian.org>
Cc:     Christoph Hellwig <hch@....de>, io-uring@...r.kernel.org,
        linux-nvme@...ts.infradead.org, asml.silence@...il.com,
        axboe@...nel.dk, leit@...com, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, sagi@...mberg.me, kbusch@...nel.org,
        ming.lei@...hat.com
Subject: Re: [PATCH 1/2] io_uring: Pass whole sqe to commands

On Thu, Apr 20, 2023 at 05:29:18AM -0700, Breno Leitao wrote:
> > > -	cmd_size = uring_cmd_pdu_size(req->ctx->flags & IORING_SETUP_SQE128);
> > > +	if (req->ctx->flags & IORING_SETUP_SQE128)
> > > +		size <<= 1;
> > 
> > 
> > Why does this stop using uring_cmd_pdu_size()?
> 
> Before, only the cmd payload (sqe->cmd) was being copied to the async
> structure. We are copying over the whole sqe now, since we can use SQE
> fields inside the ioctl callbacks (instead of only cmd fields). So, the
> copy now is 64 bytes for single SQE or 128 for double SQEs.

That's the point of this series and I get it.  But why do we remove
the nice and self-documenting helper that returns once or twice
the sizeof of the SQE structure and instead add a magic open coded
left shift?