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From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH 1/1] io_uring: fix leaks on IOPOLL and CQE_SKIP
Date: Tue, 12 Apr 2022 10:46:47 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

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


  reply	other threads:[~2022-04-12 16:46 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-12 16:24 [PATCH 1/1] io_uring: fix leaks on IOPOLL and CQE_SKIP Pavel Begunkov
2022-04-12 16:41 ` Jens Axboe
2022-04-12 16:46   ` Jens Axboe [this message]
2022-04-15 21:05     ` Pavel Begunkov
2022-04-15 22:03       ` Jens Axboe
2022-04-15 22:41         ` Pavel Begunkov
2022-04-15 22:53           ` Jens Axboe
2022-04-15 23:51             ` Jens Axboe
2022-04-16  8:36               ` Pavel Begunkov
2022-04-16  8:39             ` Pavel Begunkov
2022-04-16 13:23               ` Jens Axboe
2022-04-16  8:34           ` Pavel Begunkov

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