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

On 1/28/19 5:58 PM, Jann Horn wrote:

On Tue, Jan 29, 2019 at 1:55 AM Jens Axboe [off-list ref] wrote:

quoted

On 1/28/19 5:34 PM, Jann Horn wrote:

quoted

On Tue, Jan 29, 2019 at 1:32 AM Jens Axboe [off-list ref] wrote:

quoted

On 1/28/19 5:03 PM, Jens Axboe wrote:

quoted

quoted

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.

Why not? kvm_create_vm() does it, too:

    mmgrab(current->mm);
    kvm->mm = current->mm;

I missed that helper, was only looking at mmget(). But yeah, that'll do it!

-- 
Jens Axboe

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