[PATCH 4.6 073/121] mm/compaction.c: fix zoneindex in kcompactd()

From: Greg Kroah-Hartman
Date: Sun Jun 05 2016 - 17:57:59 EST

4.6-stable review patch. If anyone has any objections, please let me know.


From: Chen Feng <puck.chen@xxxxxxxxxxxxx>

commit 6cd9dc3e75078ef646076fa63adfb9b85ced0b66 upstream.

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 <=.

It fixes a regression where kswapd could previously compact, but
kcompactd not. Not a crash fix though.

[akpm@xxxxxxxxxxxxxxxxxxxx: fix kcompactd_do_work() as well, per Hugh]
Link: http://lkml.kernel.org/r/1463659121-84124-1-git-send-email-puck.chen@xxxxxxxxxxxxx
Fixes: accf62422b3a ("mm, kswapd: replace kswapd compaction with waking up kcompactd")
Signed-off-by: Chen Feng <puck.chen@xxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Zhuangluan Su <suzhuangluan@xxxxxxxxxxxxx>
Cc: Yiping Xu <xuyiping@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

mm/compaction.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1742,7 +1742,7 @@ static bool kcompactd_node_suitable(pg_d
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))
@@ -1777,7 +1777,7 @@ static void kcompactd_do_work(pg_data_t

- for (zoneid = 0; zoneid < cc.classzone_idx; zoneid++) {
+ for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) {
int status;

zone = &pgdat->node_zones[zoneid];