---
CAUTION: due to the time of day, I have only COMPILE tested this code

 include/linux/mmzone.h |    4 ++++
 mm/compaction.c        |   25 +++++++++++++++++++++++--
 mm/internal.h          |    1 +
 mm/page_alloc.c        |    4 ++++
 4 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 2427706..b8a5c36 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h

@@ -369,6 +369,10 @@ struct zone {
 	 */
 	spinlock_t		lock;
 	int                     all_unreclaimable; /* All pages pinned */
+#if defined CONFIG_COMPACTION || defined CONFIG_CMA
+	/* pfn where the last order > 0 compaction isolated free pages */
+	unsigned long		last_free_pfn;
+#endif

 #ifdef CONFIG_MEMORY_HOTPLUG
 	/* see spanned/present_pages for more description */
 	seqlock_t		span_seqlock;

diff --git a/mm/compaction.c b/mm/compaction.c
index 7ea259d..0e9e995 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c

@@ -422,6 +422,10 @@ static void isolate_freepages(struct zone *zone,
 					pfn -= pageblock_nr_pages) {
 		unsigned long isolated;
 
+		/* Skip ahead if somebody else is compacting simultaneously. */
+		if (cc->order > 0)
+			pfn = min(pfn, zone->last_free_pfn);
+
 		if (!pfn_valid(pfn))
 			continue;
 

@@ -463,6 +467,8 @@ static void isolate_freepages(struct zone *zone,
 		 */
 		if (isolated)
 			high_pfn = max(high_pfn, pfn);
+		if (cc->order > 0)
+			zone->last_free_pfn = high_pfn;
 	}
 
 	/* split_free_page does not map the pages */

@@ -565,9 +571,24 @@ static int compact_finished(struct zone *zone,
 	if (fatal_signal_pending(current))
 		return COMPACT_PARTIAL;
 
-	/* Compaction run completes if the migrate and free scanner meet */
-	if (cc->free_pfn <= cc->migrate_pfn)
+	/*
+	 * A full (order == -1) compaction run starts at the beginning and
+	 * end of a zone; it completes when the migrate and free scanner meet. 
+	 * A partial (order > 0) compaction can start with the free scanner
+	 * at a random point in the zone, and may have to restart.
+	 */
+	if (cc->free_pfn <= cc->migrate_pfn) {
+		if (cc->order > 0 && !cc->last_round) {
+			/* We started partway through; restart at the end. */
+			unsigned long free_pfn;
+			free_pfn = zone->zone_start_pfn + zone->spanned_pages;
+			free_pfn &= ~(pageblock_nr_pages-1);
+			zone->last_free_pfn = free_pfn;
+			cc->last_round = 1;
+			return COMPACT_CONTINUE;
+		}
 		return COMPACT_COMPLETE;
+	}
 
 	/*
 	 * order == -1 is expected when compacting via

diff --git a/mm/internal.h b/mm/internal.h
index 2ba87fb..b041874 100644
--- a/mm/internal.h
+++ b/mm/internal.h

@@ -120,6 +120,7 @@ struct compact_control {
 	unsigned long free_pfn;		/* isolate_freepages search base */
 	unsigned long migrate_pfn;	/* isolate_migratepages search base */
 	bool sync;			/* Synchronous migration */
+	bool last_round;		/* Last round for order>0 compaction */
 

 	int order;			/* order a direct compactor needs */
 	int migratetype;		/* MOVABLE, RECLAIMABLE etc */

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4403009..86de652 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -4394,6 +4394,10 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
 
 		zone->spanned_pages = size;
 		zone->present_pages = realsize;
+#if defined CONFIG_COMPACTION || defined CONFIG_CMA
+		zone->last_free_pfn = zone->zone_start_pfn + zone->spanned_pages;
+		zone->last_free_pfn &= ~(pageblock_nr_pages-1);
+#endif
 #ifdef CONFIG_NUMA
 		zone->node = nid;
 		zone->min_unmapped_pages = (realsize*sysctl_min_unmapped_ratio)