Re: [PATCH v2 2/5] userfaultfd: non-cooperative: add event for memory unmaps

[Mike Rapoport]

On Tue, Jan 31, 2017 at 04:39:28PM -0800, Andrew Morton wrote:
> On Fri, 27 Jan 2017 20:44:30 +0200 Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> wrote:
> 
> > When a non-cooperative userfaultfd monitor copies pages in the background,
> > it may encounter regions that were already unmapped. Addition of
> > UFFD_EVENT_UNMAP allows the uffd monitor to track precisely changes in the
> > virtual memory layout.
> > 
> > Since there might be different uffd contexts for the affected VMAs, we
> > first should create a temporary representation for the unmap event for each
> > uffd context and then notify them one by one to the appropriate userfault
> > file descriptors.
> > 
> > The event notification occurs after the mmap_sem has been released.
> 
> I was going to bug you about not updating
> Documentation/vm/userfaultfd.txt but the UFFD_FEATURE flags aren't
> documented?
 
I'm going to send the documentation update in the next few days.

--
Sincerely yours,
Mike.