[PATCH 4/5] mm: memcg revert upstream all_unreclaimable() use zone->all_unreclaimable as a name

[Ying Han <yinghan@google.com>]

The upstream change reverts the other change as listed below:

commit d1908362ae0b97374eb8328fbb471576332f9fb1
Author: Minchan Kim <minchan.kim@gmail.com>
Date:   Wed Sep 22 13:05:01 2010 -0700

    vmscan: check all_unreclaimable in direct reclaim path

The zone->all_unreclaimable flag is set by kswapd by checking zone->pages_scanned in
zone_reclaimable(). It is possible to have zone->all_unreclaimable == false while
the zone is actually unreclaimable, and it will cause machine to stuck.

1. while kswapd in reclaim priority loop, someone frees a page on the zone. It
will end up resetting the pages_scanned.

2. kswapd is frozen for whatever reason. This happens in hibernation where we are
not interested in google.

Especially we need to keep Minchan's patch after the softlimit reclaim support.
On a system which over-commit the softlimit, it is easily to make the system hang
w/o it.

Signed-off-by: Ying Han <yinghan@google.com>
---
 mm/vmscan.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5d036f5..65febc1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2318,6 +2318,7 @@ static bool all_unreclaimable(struct zonelist *zonelist,
 {
 	struct zoneref *z;
 	struct zone *zone;
+	bool all_unreclaimable = true;
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 			gfp_zone(sc->gfp_mask), sc->nodemask) {
@@ -2325,11 +2326,13 @@ static bool all_unreclaimable(struct zonelist *zonelist,
 			continue;
 		if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
 			continue;
-		if (!zone->all_unreclaimable)
-			return false;
+		if (zone_reclaimable(zone)) {
+			all_unreclaimable = false;
+			break;
+		}
 	}
 
-	return true;
+	return all_unreclaimable;
 }
 
 /*
-- 
1.7.7.3

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