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

[Jens Axboe <axboe@kernel.dk>]

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.

-- 
Jens Axboe