Re: [PATCH v3 4/4] io_uring: add support for zone-append

Matthew Wilcox
2020-07-08T15:03:34Z

On Wed, Jul 08, 2020 at 08:59:50AM -0600, Jens Axboe wrote:
> On 7/8/20 8:58 AM, Matthew Wilcox wrote:
> > On Wed, Jul 08, 2020 at 08:54:07AM -0600, Jens Axboe wrote:
> >> On 7/8/20 6:58 AM, Kanchan Joshi wrote:
> >>>>> +#define IOCB_NO_CMPL (15 << 28)
> >>>>>
> >>>>> struct kiocb {
> >>>>> [...]
> >>>>> - void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
> >>>>> + loff_t __user *ki_uposp;
> >>>>> - int ki_flags;
> >>>>> + unsigned int ki_flags;
> >>>>>
> >>>>> +typedef void ki_cmpl(struct kiocb *, long ret, long ret2);
> >>>>> +static ki_cmpl * const ki_cmpls[15];
> >>>>>
> >>>>> +void ki_complete(struct kiocb *iocb, long ret, long ret2)
> >>>>> +{
> >>>>> + unsigned int id = iocb->ki_flags >> 28;
> >>>>> +
> >>>>> + if (id < 15)
> >>>>> + ki_cmpls[id](iocb, ret, ret2);
> >>>>> +}
> >>>>>
> >>>>> +int kiocb_cmpl_register(void (*cb)(struct kiocb *, long, long))
> >>>>> +{
> >>>>> + for (i = 0; i < 15; i++) {
> >>>>> + if (ki_cmpls[id])
> >>>>> + continue;
> >>>>> + ki_cmpls[id] = cb;
> >>>>> + return id;
> >>>>> + }
> >>>>> + WARN();
> >>>>> + return -1;
> >>>>> +}
> >>>>
> >>>> That could work, we don't really have a lot of different completion
> >>>> types in the kernel.
> >>>
> >>> Thanks, this looks sorted.
> >>
> >> Not really, someone still needs to do that work. I took a quick look, and
> >> most of it looks straight forward. The only potential complication is
> >> ocfs2, which does a swap of the completion for the kiocb. That would just
> >> turn into an upper flag swap. And potential sync kiocb with NULL
> >> ki_complete. The latter should be fine, I think we just need to reserve
> >> completion nr 0 for being that.
> >
> > I was reserving completion 15 for that ;-)
> >
> > +#define IOCB_NO_CMPL (15 << 28)
> > ...
> > + if (id < 15)
> > + ki_cmpls[id](iocb, ret, ret2);
> >
> > Saves us one pointer in the array ...
>
> That works. Are you going to turn this into an actual series of patches,
> adding the functionality and converting users?

I was under the impression Kanchan was going to do that, but I can run it
off quickly ...