On Tue, Jan 31, 2017 at 04:41:32PM -0800, Andrew Morton wrote:
> On Fri, 27 Jan 2017 20:44:31 +0200 Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> wrote:
>
> > Allow userfaultfd monitor track termination of the processes that have
> > memory backed by the uffd.
> >
> > --- a/fs/userfaultfd.c
> > +++ b/fs/userfaultfd.c
> > @@ -774,6 +774,30 @@ void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
> > }
> > }
> >
> > +void userfaultfd_exit(struct mm_struct *mm)
> > +{
> > + struct vm_area_struct *vma = mm->mmap;
> > +
> > + while (vma) {
> > + struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
> > +
> > + if (ctx && (ctx->features & UFFD_FEATURE_EVENT_EXIT)) {
> > + struct userfaultfd_wait_queue ewq;
> > +
> > + userfaultfd_ctx_get(ctx);
> > +
> > + msg_init(&ewq.msg);
> > + ewq.msg.event = UFFD_EVENT_EXIT;
> > +
> > + userfaultfd_event_wait_completion(ctx, &ewq);
> > +
> > + ctx->features &= ~UFFD_FEATURE_EVENT_EXIT;
> > + }
> > +
> > + vma = vma->vm_next;
> > + }
> > +}
>
> And we can do the vma walk without locking because the caller (exit_mm)
> knows it now has exclusive access. Worth a comment?
Sure, will add. Do you prefer an incremental patch or update this one?
--
Sincerely yours,
Mike.
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