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.
