Re: [PATCH] mm: compact: fix zoneindex in compact

[Hugh Dickins]

On Thu, 19 May 2016, Vlastimil Babka wrote:
> On 05/19/2016 02:11 PM, Vlastimil Babka wrote:
> > On 05/19/2016 01:58 PM, Chen Feng wrote:
> >> While testing the kcompactd in my platform 3G MEM only DMA ZONE.
> >> I found the kcompactd never wakeup. It seems the zoneindex
> >> has already minus 1 before. So the traverse here should be <=.
> > 
> > Ouch, thanks!
> > 
> >> Signed-off-by: Chen Feng <puck.chen@xxxxxxxxxxxxx>
> > 
> > Fixes: 0f87baf4f7fb ("mm: wake kcompactd before kswapd's short sleep")
> 
> Bah, not that one.
> 
> Fixes: accf62422b3a ("mm, kswapd: replace kswapd compaction with waking
> up kcompactd")
> 
> > Cc: stable@xxxxxxxxxxxxxxx
> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> > 
> >> ---
> >>  mm/compaction.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/mm/compaction.c b/mm/compaction.c
> >> index 8fa2540..e5122d9 100644
> >> --- a/mm/compaction.c
> >> +++ b/mm/compaction.c
> >> @@ -1742,7 +1742,7 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat)
> >>  	struct zone *zone;
> >>  	enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
> >>  
> >> -	for (zoneid = 0; zoneid < classzone_idx; zoneid++) {
> >> +	for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
> >>  		zone = &pgdat->node_zones[zoneid];
> >>  
> >>  		if (!populated_zone(zone))

Ignorant question: kcompactd_do_work() just below has a similar loop:
should that one be saying "zoneid <= cc.classzone_idx" too?

Hugh