On Tue, Jan 29, 2019 at 1:55 AM Jens Axboe <axboe@xxxxxxxxx> wrote:
> 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.
Why not? kvm_create_vm() does it, too:
mmgrab(current->mm);
kvm->mm = current->mm;
> But I think
> we can get around this by using an mmu notifier instead. That eliminates
> the need for ->flush() as well.
