Re: [PATCH] migration: migrate_vmas should check "vma"

[Daisuke Nishimura]

On Thu, 29 Jan 2009 00:18:49 -0800, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 29 Jan 2009 10:16:23 +0900 Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote:
> 
> > On Wed, 28 Jan 2009 17:55:12 +0100, Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
> > > On Wed, Jan 28, 2009 at 11:42:36AM -0500, Christoph Lameter wrote:
> > > > On Wed, 28 Jan 2009, Daisuke Nishimura wrote:
> > > > 
> > > > > migrate_vmas() should check "vma" not "vma->vm_next" for for-loop condition.
> > > > 
> > > > The loop condition is checked before vma = vma->vm_next. So the last
> > > > iteration of the loop will now be run with vma = NULL?
> > > 
> > > No, the condition is always checked before the body is executed.  The
> > > assignment to vma->vm_next happens at the end of every body.
> > > 
> > So, I think in current code the loop body is not executed
> > about the last vma in the list.
> > 
> 
> Yep.
> 
> Is this serious enough to bother fixing in 2.6.29?
IIUC, there is no user of vm_ops->migrate() now, so this bug causes
no practical problems.

I think it's trival and simple enough to go in .29, but I don't have
any objection if you postpone this patch.


Thanks,
Daisuke Nishimura.
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