Re: [PATCHv5 07/11] io_uring: add support for kernel registered bvecs

[Keith Busch <kbusch@kernel.org>]

On Wed, Feb 26, 2025 at 06:47:54AM +0800, Ming Lei wrote:
> On Wed, Feb 26, 2025 at 1:32 AM Keith Busch <kbusch@kernel.org> wrote:
> >
> > 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.
> 
> But IMU represents a buffer, and the buffer could be used for other
> OPs in future,
> instead of write command only. Here it is more readable to mark the buffer
> readable or writable.
> 
> I'd suggest not introducing the confusion from the beginning.

Absolutely, no disagreement here. My next version calls the flags
"IO_IMU_SOURCE" and "IO_IMU_DEST" and defined from the same ITER_
values.