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

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