Re: [PATCH 1/1] io_uring: fix leaks on IOPOLL and CQE_SKIP

[Pavel Begunkov <asml.silence@gmail.com>]

On 4/12/22 17:46, Jens Axboe wrote:
> On 4/12/22 10:41 AM, Jens Axboe wrote:
>> On 4/12/22 10:24 AM, Pavel Begunkov wrote:
>>> If all completed requests in io_do_iopoll() were marked with
>>> REQ_F_CQE_SKIP, we'll not only skip CQE posting but also
>>> io_free_batch_list() leaking memory and resources.
>>>
>>> Move @nr_events increment before REQ_F_CQE_SKIP check. We'll potentially
>>> return the value greater than the real one, but iopolling will deal with
>>> it and the userspace will re-iopoll if needed. In anyway, I don't think
>>> there are many use cases for REQ_F_CQE_SKIP + IOPOLL.
>>
>> Ah good catch - yes probably not much practical concern, as the lack of
>> ordering for file IO means that CQE_SKIP isn't really useful for that
>> scenario.
> 
> One potential snag is with the change we're now doing
> io_cqring_ev_posted_iopoll() even if didn't post an event. Again
> probably not a practical concern, but it is theoretically a violation
> if an eventfd is used.
Looks this didn't get applied. Are you concerned about eventfd?
Is there any good reason why the userspace can't tolerate spurious
eventfd events? Because I don't think we should care this case

-- 
Pavel Begunkov