Re: [PATCH] page allocator: fix update NR_FREE_PAGES only as necessary

[Christoph Lameter <cl@linux-foundation.org>]

On Mon, 4 Jan 2010, Mel Gorman wrote:

> > Why can't we write following? __mod_zone_page_state() only require irq
> > disabling, it doesn't need spin lock. I think.

Correct.

> > commit f2260e6b (page allocator: update NR_FREE_PAGES only as necessary)
> > made one minor regression.
> > if __rmqueue() was failed, NR_FREE_PAGES stat go wrong. this patch fixes
> > it.
> >
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > Cc: Mel Gorman <mel@csn.ul.ie>
> > Cc: Huang Shijie <shijie8@gmail.com>
> > Cc: Minchan Kim <minchan.kim@gmail.com>
> > ---
> >  mm/page_alloc.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 11ae66e..ecf75a1 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1227,10 +1227,10 @@ again:
> >  		}
> >  		spin_lock_irqsave(&zone->lock, flags);
> >  		page = __rmqueue(zone, order, migratetype);
> > -		__mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << order));
> >  		spin_unlock(&zone->lock);
> >  		if (!page)
> >  			goto failed;
> > +		__mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << order));
> >  	}
> >
> >  	__count_zone_vm_events(PGALLOC, zone, 1 << order);

Reviewed-by: Christoph Lameter <cl@linux-foundation.org>

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