On Tue, Jul 01, 2014 at 03:33:44PM -0400, Jerome Glisse wrote:
> On Tue, Jul 01, 2014 at 01:00:18PM +0200, Joerg Roedel wrote:
> > No, its not in this case. The file descriptor is used to connect a
> > process address space with a device context. Thus without the mappings
> > the file-descriptor is useless and the mappings should stay in-tact
> > until the fd is closed.
> >
> > It would be a very bad semantic for userspace if a fd that is passed on
> > fails on the other side because the sending process died.
>
> Consider use case where there is no file associated with the mmu_notifier
> ie there is no device file descriptor that could hold and take care of
> mmu_notifier destruction and cleanup. We need this call chain for this
> case.
Example of such a use-case where no fd will be associated?
Anyway, even without an fd, there will always be something that sets the
mm->device binding up (calling mmu_notifier_register) and tears it down
in the end (calling mmu_notifier_unregister). And this will be the
places where any resources left from the .release call-back can be
cleaned up.
Joerg
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