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

[Christoph Hellwig]

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?