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.
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