Jens Axboe <axboe@xxxxxxxxx> writes: > On 10/20/21 12:16 PM, Jeff Moyer wrote: >> Hi, Jens, >> >> Jens Axboe <axboe@xxxxxxxxx> writes: >> >>> It's not used for anything, and we're wasting time passing in zeroes >>> where we could just ignore it instead. Update all ki_complete users in >>> the kernel to drop that last argument. >> >> What does "wasting time passing in zeroes" mean? > > That everybody but the funky usb gadget code passes in zero, hence it's > a waste of time to pass it in as an argument. OK. Just making sure you hadn't found some performance gain from this. :) >> We can't know whether some userspace implementation relies on this >> behavior, so I don't think you can change it. > > Well, I think we should find out, particularly as it's the sole user of > that extra argument. How can we find out? Anyone can write userspace usb gadget code. Some of those users may be proprietary. Is that likely? I don't know. I'd rather err on the side of not (potentially) breaking existing applications, though. > No generic aio code would look at res2, exactly because it is always > zero for anything but some weird usb gadget code. I think that no generic code looks at it because it isn't meant to be interpreted by generic code. :) -Jeff
