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Date:   Mon, 24 Apr 2023 07:08:43 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Breno Leitao <leitao@debian.org>
Cc:     Christoph Hellwig <hch@lst.de>, io-uring@vger.kernel.org,
        linux-nvme@lists.infradead.org, asml.silence@gmail.com,
        axboe@kernel.dk, leit@fb.com, linux-kernel@vger.kernel.org,
        linux-block@vger.kernel.org, sagi@grimberg.me, kbusch@kernel.org,
        ming.lei@redhat.com
Subject: Re: [PATCH 1/2] io_uring: Pass whole sqe to commands
Message-ID: <20230424050843.GA9252@lst.de>
References: <20230419102930.2979231-1-leitao@debian.org> <20230419102930.2979231-2-leitao@debian.org> <20230420045712.GA4239@lst.de> <ZEKno++WWPauufw0@gmail.com>
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On Fri, Apr 21, 2023 at 08:11:31AM -0700, Breno Leitao wrote:
> On Thu, Apr 20, 2023 at 06:57:12AM +0200, Christoph Hellwig wrote:
> > On Wed, Apr 19, 2023 at 03:29:29AM -0700, Breno Leitao wrote:
> > >  	struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
> > > -	const struct nvme_uring_cmd *cmd = ioucmd->cmd;
> > > +	const struct nvme_uring_cmd *cmd = (struct nvme_uring_cmd *)ioucmd->sqe->cmd;
> > 
> > Please don't add the pointless cast.  And in general avoid the overly
> > long lines.
> 
> If I don't add this cast, the compiler complains with the follow error:
> 
> 	drivers/nvme/host/ioctl.c: In function ‘nvme_uring_cmd_io’:
> 	drivers/nvme/host/ioctl.c:555:37: error: initialization of ‘const struct nvme_uring_cmd *’ from incompatible pointer type ‘const __u8 *’ {aka ‘const unsigned char *’} [-Werror=incompatible-pointer-types]
> 	  const struct nvme_uring_cmd *cmd = ioucmd->sqe->cmd;

Oh.  I think then we need a helper to get the private data from
the io_uring_cmd as an interface that requires casts in all callers
is one asking for bugs.