linux-kernel - Re: [PATCH v2 4/4] mm: make unreserve highatomic functions reliable

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Date:   Wed, 12 Oct 2016 16:48:38 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Michal Hocko <mhocko@...nel.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Sangseok Lee <sangseok.lee@....com>
Subject: Re: [PATCH v2 4/4] mm: make unreserve highatomic functions reliable

On Wed, Oct 12, 2016 at 09:33:28AM +0200, Michal Hocko wrote:
> On Wed 12-10-16 14:33:36, Minchan Kim wrote:
> [...]
> > @@ -2138,8 +2146,10 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac)
> >  			 */
> >  			set_pageblock_migratetype(page, ac->migratetype);
> >  			ret = move_freepages_block(zone, page, ac->migratetype);
> > -			spin_unlock_irqrestore(&zone->lock, flags);
> > -			return ret;
> > +			if (!drain && ret) {
> > +				spin_unlock_irqrestore(&zone->lock, flags);
> > +				return ret;
> > +			}
> 
> I've already mentioned that during the previous discussion. This sounds

Yeb, we did but I sent wrong version in my git tree. :(

> overly aggressive to me. Why do we want to drain the whole reserve and
> risk that we won't be able to build up a new one after OOM. Doing one
> block at the time should be sufficient IMHO.

I will resend with updating with every reveiw points.

Thanks.