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?
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