Re: [PATCH 0/5] "task_work for links" fixes

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

On 29/06/2020 18:52, Jens Axboe wrote:
> On 6/29/20 4:21 AM, Pavel Begunkov wrote:
>> On 28/06/2020 17:46, Pavel Begunkov wrote:
>>> On 28/06/2020 16:49, Jens Axboe wrote:
>>>> On 6/27/20 5:04 AM, Pavel Begunkov wrote:
>>>>> All but [3/5] are different segfault fixes for
>>>>> c40f63790ec9 ("io_uring: use task_work for links if possible")
>>>>
>>>> Looks reasonable, too bad about the task_work moving out of the
>>>> union, but I agree there's no other nice way to avoid this. BTW,
>>>> fwiw, I've moved that to the head of the series.
>>>
>>> I think I'll move it back, but that would need more work to be
>>> done. I've described the idea in the other thread.
>>
>> BTW, do you know any way to do grab_files() from task_work context?
>> The problem is that nobody sets ctx->ring_{fd,file} there. Using stale
>> values won't do, as ring_fd can be of another process at that point.
> 
> We probably have to have them grabbed up-front. Which should be easy
> enough to do now, since task_work and work are no longer in a union.

Yep, and it's how it's done. Just looking how to handle req.work better.
e.g. if we can grab_files() from task_work, then it's one step from
moving back req.work into union + totally removing memcpy(work, apoll)
from io_arm_poll_handler().

-- 
Pavel Begunkov