Re: vDSO vs. mm : problems with ppc vdso

Hugh Dickins
2006-02-28T12:32:04Z

On Tue, 28 Feb 2006, Nick Piggin wrote:
>
> You should be OK. VM_RESERVED itself is something of an anachronism
> these days. If you're not getting your page from the page allocator
> then you'll want to make sure each of their count, and mapcount is
> reset before allowing them to be mapped.

Yes, it's fine that VM_RESERVED isn't set on it.
But I don't understand your remarks about count and mapcount at all:
perhaps you meant to say something else?

If I ignore what you actually said, and think of what problems there
might be in that area, then yes, if the pages come from kernel memory
(they do) rather than page allocator, we'd better make sure page_count
starts above 0, so it doesn't go down to zero on last free from userspace:
and indeed, Ben's vdso_init does a get_page on each to ensure that.

Hugh