Re: [patch] mm: unlockless reclaim

[Nick Piggin <npiggin@suse.de>]

On Tue, Aug 19, 2008 at 02:09:07PM +0900, KOSAKI Motohiro wrote:
> > -		unlock_page(page);
> > +		/*
> > +		 * At this point, we have no other references and there is
> > +		 * no way to pick any more up (removed from LRU, removed
> > +		 * from pagecache). Can use non-atomic bitops now (and
> > +		 * we obviously don't have to worry about waking up a process
> > +		 * waiting on the page lock, because there are no references.
> > +		 */
> > +		__clear_page_locked(page);
> >  free_it:
> >  		nr_reclaimed++;
> >  		if (!pagevec_add(&freed_pvec, page)) {
> > 
> 
> To insert VM_BUG_ON(page_count(page) != 1) is better?
> Otherthing, looks good to me.

That is a very good idea, except that now with lockless pagecache, we're
not so well placed to do this type of check. Actually at this point,
the refcount will be 0 because of page_freeze_refs, and then if anybody
else tries to do a get_page, they should hit the VM_BUG_ON in get_page.

 
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Thanks for looking at it.

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