Re: [GIT PULL] please pull ummunotify

KOSAKI Motohiro
2009-09-11T06:21:35Z

> Roland Dreier wrote:
> > > Can I this version already solved fork() + COW issue? if so, could you
> > > please explain what happen at fork. Obviously RDMA point to either parent
> > > or child page, not both. but Corrent COW rule is, first touch process
> > > get copyed page and other process still own original page. I think it's
> > > unpecected behavior form RDMA.
> >
> > No, ummunotify doesn't really help that much with fork() + COW. If a
> > parent forks and then touches pages that are actively in use for RDMA,
> > then of course they get COWed and RDMA goes to the wrong memory (from
> > the point of view of the parent).
> >
>
> My understanding of the code is that fork will end-up calling
> copy_page_range() on all VMA, and copy_page_range() calls
> mmu_notifier_invalidate_range_start() if is_cow_mapping() is true,
> which should be the case here. So you should get some invalidate events
> on fork.

Worried...
Anybody haven't test fork() case yet???