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

Matthew Wilcox
2020-07-10T13:51:29Z

On Fri, Jul 10, 2020 at 02:49:32PM +0100, Christoph Hellwig wrote:
> On Fri, Jul 10, 2020 at 02:48:24PM +0100, Matthew Wilcox wrote:
> > If we're going to go the route of changing the CQE, how about:
> >
> > struct io_uring_cqe {
> > __u64 user_data; /* sqe->data submission passed back */
> > - __s32 res; /* result code for this event */
> > - __u32 flags;
> > + union {
> > + struct {
> > + __s32 res; /* result code for this event */
> > + __u32 flags;
> > + };
> > + __s64 res64;
> > + };
> > };
> >
> > then we don't need to change the CQE size and it just depends on the SQE
> > whether the CQE for it uses res+flags or res64.
>
> How do you return a status code or short write when you just have
> a u64 that is needed for the offset?

it's an s64 not a u64 so you can return a negative errno. i didn't
think we allowed short writes for objects-which-have-a-pos.