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

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Date:	Sun,  5 Jun 2016 14:43:45 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Chen Feng <puck.chen@...ilicon.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Hugh Dickins <hughd@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Tejun Heo <tj@...nel.org>,
	Zhuangluan Su <suzhuangluan@...ilicon.com>,
	Yiping Xu <xuyiping@...ilicon.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.6 073/121] mm/compaction.c: fix zoneindex in kcompactd()

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

------------------

From: Chen Feng <puck.chen@...ilicon.com>

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

---
 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
 							cc.classzone_idx);
 	count_vm_event(KCOMPACTD_WAKE);

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

 		zone = &pgdat->node_zones[zoneid];