Re: [PATCH] io_uring: add IORING_OP_NOP_FAIL

[Ming Lei <ming.lei@redhat.com>]

On Thu, May 9, 2024 at 11:05 AM Ming Lei <ming.lei@redhat.com> wrote:
>
> On Wed, May 08, 2024 at 08:55:09PM -0600, Jens Axboe wrote:
> > On 5/8/24 8:34 PM, Ming Lei wrote:
> > > Add IORING_OP_NOP_FAIL so that it is easy to inject failure from
> > > userspace.
> > >
> > > Like IORING_OP_NOP, the main use case is test, and it is very helpful
> > > for covering failure handling code in io_uring core change.
> >
> > Rather than use a new opcode for this, why don't we just add it to
> > the existing NOP? I know we don't check for flags in currently, so
> > you would not know if it worked, but we could add that and just
> > backport that one-liner as well.
>
> Yeah, it is just for avoiding to break existed tests which may not build
> over liburing.
>
> I will switch to this way, looks one-line backporting can solve it.

I guess backporting can't work, because application code expects
NOP to complete successfully with and w/o non-zero sqe->rw_flags.

However, the backport has to fail NOP in case of non-zero sqe->rw_flags.

Thanks.