Re: [PATCH 0/2] Remove kiocb ki_complete

Matthew Wilcox
2020-07-09T13:32:53Z

On Thu, Jul 09, 2020 at 02:26:11PM +0100, Christoph Hellwig wrote:
> On Thu, Jul 09, 2020 at 12:10:36PM +0100, Matthew Wilcox wrote:
> > On Thu, Jul 09, 2020 at 11:17:05AM +0100, Christoph Hellwig wrote:
> > > I really don't like this series at all. If saves a single pointer
> > > but introduces a complicated machinery that just doesn't follow any
> > > natural flow. And there doesn't seem to be any good reason for it to
> > > start with.
> >
> > Jens doesn't want the kiocb to grow beyond a single cacheline, and we
> > want the ability to set the loff_t in userspace for an appending write,
> > so the plan was to replace the ki_complete member in kiocb with an
> > loff_t __user *ki_posp.
> >
> > I don't think it's worth worrying about growing kiocb, personally,
> > but this seemed like the easiest way to make room for a new pointer.
>
> The user offset pointer has absolutely no business in the the kiocb
> itself - it is a io_uring concept which needs to go into the io_kiocb,
> which has 14 bytes left in the last cache line in my build. It would
> fit in very well there right next to the result and user pointer.

I agree. Jens doesn't.