Re: memory unplug v4 intro [1/6] migration without mm->sem

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Thu, 7 Jun 2007 22:57:19 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:

> > Ah, maybe ok. But scattering codes around rmap in several files is ok ?
> 
> No. Lets try to keep the changes to rmap minimal.
> 
Okay, will do my best.

> > > Could you avoid these checks by having page_referend_one fail
> > > appropriately on the dummy vma?
> > > 
> > Hmm, Is this better ?
> > ==
> > static int page_referenced_one(struct page *page,
> >         struct vm_area_struct *vma, unsigned int *mapcount)
> > {
> >         struct mm_struct *mm = vma->vm_mm;
> >         unsigned long address;
> >         pte_t *pte;
> >         spinlock_t *ptl;
> >         int referenced = 0;
> > 
> > +	if(is_dummy_vma(vma))
> > +		return 0;
> 
> The best solution would be if you could fill the dummy vma with such 
> values that will give you the intended result without having to modify 
> page_referenced_one. If you can make vma_address() fail then you have 
> what you want. F.e. setting vma->vm_end to zero should do it. (is it not 
> already zero?)
> 
> 
Hmm, maybe your option will work. I'll try it in the next set.
My concern is that almost all people will never imagine anon_vma can includes
dummy_vma in some special case..

-Kame


-Kame

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