[openib-general] Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation

[Roland Dreier]

OK, I'm by no means an expert on this, but Libor and I looked at
rmap.c a little more, and there is code:

	if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) ||
			ptep_clear_flush_young(vma, address, pte)) {
		ret = SWAP_FAIL;
		goto out_unmap;
	}

before the check

	if (PageSwapCache(page) &&
	    page_count(page) != page_mapcount(page) + 2) {
		ret = SWAP_FAIL;
		goto out_unmap;
	}

If userspace allocates some memory but doesn't touch it aside from
passing the address in to the kernel, which does get_user_pages(), the
PTE will be young in that first test, right?  Does that mean that
the userspace mapping will be cleared and userspace will get a
different physical page if it faults that address back in?

 - R.