linux-kernel - Re: [PATCH] mm/vmscan: fix highidx argument type

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Date:	Fri, 16 Jan 2015 09:07:44 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Rik van Riel <riel@...hat.com>,
	Michal Hocko <mhocko@...e.cz>, Mel Gorman <mgorman@...e.de>,
	Vlastimil Babka <vbabka@...e.cz>,
	Suleiman Souhlal <suleiman@...gle.com>, linux-mm@...ck.org
Subject: Re: [PATCH] mm/vmscan: fix highidx argument type

On Thu, Jan 15, 2015 at 02:49:20PM -0800, Andrew Morton wrote:
> On Fri, 16 Jan 2015 00:18:12 +0200 "Michael S. Tsirkin" <mst@...hat.com> wrote:
> 
> > for_each_zone_zonelist_nodemask wants an enum zone_type
> > argument, but is passed gfp_t:
> > 
> > mm/vmscan.c:2658:9:    expected int enum zone_type [signed] highest_zoneidx
> > mm/vmscan.c:2658:9:    got restricted gfp_t [usertype] gfp_mask
> > mm/vmscan.c:2658:9: warning: incorrect type in argument 2 (different base types)
> > mm/vmscan.c:2658:9:    expected int enum zone_type [signed] highest_zoneidx
> > mm/vmscan.c:2658:9:    got restricted gfp_t [usertype] gfp_mask
> 
> Which tool emitted these warnings?

Oh, sorry.
It's sparce.

> > convert argument to the correct type.
> > 
> > ...
> >
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2656,7 +2656,7 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
> >  	 * should make reasonable progress.
> >  	 */
> >  	for_each_zone_zonelist_nodemask(zone, z, zonelist,
> > -					gfp_mask, nodemask) {
> > +					gfp_zone(gfp_mask), nodemask) {
> >  		if (zone_idx(zone) > ZONE_NORMAL)
> >  			continue;
> 
> hm, I wonder what the runtime effects are.
> 
> The throttle_direct_reclaim() comment isn't really accurate, is it? 
> "Throttle direct reclaimers if backing storage is backed by the
> network".  The code is applicable to all types of backing, but was
> added to address problems which are mainly observed with network
> backing?


As far as I can tell, yes. It would seem that it can cause
deadlocks in theory.  Cc stable on the grounds that it's obvious?

-- 
MST
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