From: Andrew Morton on
On Mon, 21 Jun 2010 16:33:49 -0400
Rik van Riel <riel(a)redhat.com> wrote:

> From: Andrea Arcangeli <aarcange(a)redhat.com>
> Subject: always add new vmas at the end
>
> Make sure to always add new VMAs at the end of the list. This
> is important so rmap_walk does not miss a VMA that was created
> during the rmap_walk.
>
> The old code got this right most of the time due to luck, but
> was buggy when anon_vma_prepare reused a mergeable anon_vma.
>
> Signed-off-by: Andrea Arcangeli <aarcange(a)redhat.com>
> Signed-off-by: Rik van Riel <riel(a)redhat.com>
> ---
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -149,7 +149,7 @@ int anon_vma_prepare(struct vm_area_stru
> avc->anon_vma = anon_vma;
> avc->vma = vma;
> list_add(&avc->same_vma, &vma->anon_vma_chain);
> - list_add(&avc->same_anon_vma, &anon_vma->head);
> + list_add_tail(&avc->same_anon_vma, &anon_vma->head);
> allocated = NULL;
> avc = NULL;
> }

Should this go into 2.6.35?
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From: Andrea Arcangeli on
On Tue, Jun 22, 2010 at 02:08:22PM -0700, Andrew Morton wrote:
> On Mon, 21 Jun 2010 16:33:49 -0400
> Rik van Riel <riel(a)redhat.com> wrote:
>
> > From: Andrea Arcangeli <aarcange(a)redhat.com>
> > Subject: always add new vmas at the end
> >
> > Make sure to always add new VMAs at the end of the list. This
> > is important so rmap_walk does not miss a VMA that was created
> > during the rmap_walk.
> >
> > The old code got this right most of the time due to luck, but
> > was buggy when anon_vma_prepare reused a mergeable anon_vma.
> >
> > Signed-off-by: Andrea Arcangeli <aarcange(a)redhat.com>
> > Signed-off-by: Rik van Riel <riel(a)redhat.com>
> > ---
> >
> > diff --git a/mm/rmap.c b/mm/rmap.c
> > --- a/mm/rmap.c
> > +++ b/mm/rmap.c
> > @@ -149,7 +149,7 @@ int anon_vma_prepare(struct vm_area_stru
> > avc->anon_vma = anon_vma;
> > avc->vma = vma;
> > list_add(&avc->same_vma, &vma->anon_vma_chain);
> > - list_add(&avc->same_anon_vma, &anon_vma->head);
> > + list_add_tail(&avc->same_anon_vma, &anon_vma->head);
> > allocated = NULL;
> > avc = NULL;
> > }
>
> Should this go into 2.6.35?

Well migrate got broken anyway in 2.6.34, so until the whole
root-anon-vma patchqueue is merged, it's not going to provide a safe
migrate anyway and it can as well wait with the rest.
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