Re: [PATCH 05/18] Add io_uring IO interface

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On 1/28/19 5:34 PM, Jann Horn wrote:
> On Tue, Jan 29, 2019 at 1:32 AM Jens Axboe <axboe@xxxxxxxxx> wrote:
>> On 1/28/19 5:03 PM, Jens Axboe wrote:
>>>> But you only do that teardown on ->release, right? And ->release
>>>> doesn't have much to do with the process lifetime.
>>>
>>> Yes, only on ->relase().
>>
>> OK, so I reworked the files struct to just grab it, then we ensure that
>> doesn't go away. For mm, it's a bit more tricky. I think the best
>> solution here is to add a fops->flush() and check for the process
>> exiting its files. If it does, we quiesce the async contexts and prevent
>> further use of that mm. We can't just keep holding a reference to the mm
>> like we do with the files.
>>
>> That should solve both cases.
> 
> You still have to hold a reference on the mm though, I think (for
> example, because two tasks might be sharing the fd table without
> sharing the mm).

Yes good point, except we can't hold a reference to it. But I think
we can get around this by using an mmu notifier instead. That eliminates
the need for ->flush() as well.

-- 
Jens Axboe




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