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Date: Tue, 25 Feb 2025 10:32:30 -0700
From: Keith Busch <kbusch@kernel.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Keith Busch <kbusch@meta.com>, asml.silence@gmail.com, axboe@kernel.dk,
	linux-block@vger.kernel.org, io-uring@vger.kernel.org,
	bernd@bsbernd.com, csander@purestorage.com
Subject: Re: [PATCHv5 07/11] io_uring: add support for kernel registered bvecs
Message-ID: <Z73-rhNw3zgvUuZr@kbusch-mbp>
References: <20250224213116.3509093-1-kbusch@meta.com>
 <20250224213116.3509093-8-kbusch@meta.com>
 <Z72P_nnZD9i-ya-1@fedora>
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In-Reply-To: <Z72P_nnZD9i-ya-1@fedora>

On Tue, Feb 25, 2025 at 05:40:14PM +0800, Ming Lei wrote:
> On Mon, Feb 24, 2025 at 01:31:12PM -0800, Keith Busch wrote:
> > +
> > +	if (op_is_write(req_op(rq)))
> > +		imu->perm = IO_IMU_WRITEABLE;
> > +	else
> > +		imu->perm = IO_IMU_READABLE;
> 
> Looks the above is wrong, if request is for write op, the buffer
> should be readable & !writeable.
> 
> IO_IMU_WRITEABLE is supposed to mean the buffer is writeable, isn't it?

In the setup I used here, IMU_WRITEABLE means this can be used in a
write command. You can write from this buffer, not to it.

I think this is the kind of ambiguity that lead iov iter to call these
buffers SOURCE and DEST instead of WRITE and READ.