On Sat, Apr 24, 2010 at 11:52:27AM +0100, Mel Gorman wrote:
> I think you're right. This is a new bug introduced by the anon_vma changes. On
> the plus side, it means we don't have to worry about -stable.

Correct, no worry about -stable.

> > vma_adjust already takes the anon_vma->lock and of course I also
> > further verified that trying to apply your snippet to vma_adjust
> > results in immediately deadlock as the very same lock is already taken
> > in my tree as it's the same anon-vma (simpler).
> 
> Yes, I expected that. Previously, there was only one anon_vma so if you
> double-take the lock, bad things happen.
> 
> > So aa.git will be
> > immune from these bugs for now.
> > 
> 
> It should be. I expect that's why you have never seen the bugon in
> swapops.

Correct, I never seen it, and I keep it under very great stress with
swap storms of hugepages, lots of I/O and khugepaged at 100% cpu.

Also keep in mind expand_downwards which also adjusts
vm_start/vm_pgoff the same way (and without mmap_sem write mode).