Messages in this thread | | | Date | Wed, 28 Apr 2010 10:18:58 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 3/3] mm,migration: Remove straggling migration PTEs when page tables are being moved after the VMA has already moved |
| |
On Wed, 28 Apr 2010 03:05:43 +0200 Andrea Arcangeli <aarcange@redhat.com> wrote:
> On Wed, Apr 28, 2010 at 09:39:48AM +0900, KAMEZAWA Hiroyuki wrote: > > Seems nice. > > What did you mean with objrmap inconsistency? I think this is single > threaded there, userland didn't run yet and I don't think page faults > could run. Maybe it's safer to add a VM_BUG_ON(vma->anon_vma) just > before vma->anon_vma = anon_vma to be sure nothing run in between. > I mean following relationship.
vma_address(vma, page1) <-> address <-> pte <-> page2
If page1 == page2, objrmap is consistent. If page1 != page2, objrmap is inconsistent.
> > I'll test this but I think we need to take care of do_mremap(), too. > > And it's more complicated.... > > do_mremap has to be safe by: > > 1) adjusting page->index atomically with the pte updates inside pt > lock (while it moves from one pte to another) > I reviewed do_mremap again and am thinking it's safe.
new_vma = copy_vma(); .... ----------(*) move_ptes(). munmap unnecessary range.
At (*), if page1 != page2, rmap_walk will not run correctly. But it seems copy_vma() keeps page1==page2
As I reported, when there is a problem, vma_address() returns an address but that address doesn't contain migration_pte.
BTW, page->index is not updated, we just keep [start_address, pgoff] to be sane value.
Thanks, -Kame
| |