From: Shaohua Li <address@hidden>
Changelog since V2
o Fix BUG_ON triggered due to pages left on cc.migratepages
o Make compact_zone_order() require non-NULL arg `contended'
Changelog since V1
o only abort the compaction if lock is contended or run too long
o Rearranged the code by Andrea Arcangeli.
isolate_migratepages_range() might isolate no pages if for example when
zone->lru_lock is contended and running asynchronous compaction. In this
case, we should abort compaction, otherwise, compact_zone will run a
useless loop and make zone->lru_lock is even contended.
address@hidden: Putback pages isolated for migration if aborting]
address@hidden: compact_zone_order requires non-NULL arg contended]
Signed-off-by: Andrea Arcangeli <address@hidden>
Signed-off-by: Shaohua Li <address@hidden>
Signed-off-by: Mel Gorman <address@hidden>