Re: [PATCH v2] io-wq: handle hashed writes in chains

Pavel Begunkov
2020-03-22T21:17:50Z

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On 22/03/2020 23:20, Pavel Begunkov wrote:
> On 22/03/2020 23:15, Jens Axboe wrote:
>> On 3/22/20 2:05 PM, Jens Axboe wrote:
>>> On 3/22/20 1:51 PM, Jens Axboe wrote:
>>>>> Please, tell if you see a hole in the concept. And as said, there is
>>>>> still a bug somewhere.
>>>
>>> One quick guess would be that you're wanting to use both work->list and
>>> work->data, the latter is used by links which is where you are crashing.
>>> Didn't check your list management yet so don't know if that's the case,
>>> but if you're still on the list (or manipulating it after), then that
>>> would be a bug.
>>
>> IOW, by the time you do work->func(&work), the item must be off the
>> list. Does indeed look like that's exactly the bug you have.
>>
>
> Good guess. I made sure to grab next before ->func(), see next_hashed. And it's
> not in @work_list, because io_get_next_work() removes it. However, somebody may
> expect it to be NULL or something. Thanks! I'll check it

You're right. Re-enqueue corrupts ->data, so should be fixed for previous
patches as well. I'll send it

--
Pavel Begunkov

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