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

Roland Dreier
2005-04-13T19:10:32Z

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.