Re: [PATCH] io_uring: add IORING_OP_NOP_FAIL

[Jens Axboe <axboe@kernel.dk>]

On 5/8/24 9:05 PM, Ming Lei 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.

Don't think that's a huge risk, if someone is using the raw interface
and just not clearing, they would run into issues with mixed command
usage anyway. And a pure nop test would be fine anyway, as everything
starts out cleared.

> I will switch to this way, looks one-line backporting can solve it.

Exactly, thanks!

>> And if we had such a flag, the fail res could be passed in as well.
> 
> We can just pass the 'injected_fail_res' via sqe->len, meantime keep
> 'nop_flags' for error injection and future extension.

Precisely.

-- 
Jens Axboe