1 files changed, 24 insertions, 5 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 9b94eaf537e4..6cc604bd5649 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -251,11 +251,18 @@ static bool too_many_isolated(struct zone *zone)
         return isolated > (inactive + active) / 2;
 }
 
+/* possible outcome of isolate_migratepages */
+typedef enum {
+        ISOLATE_ABORT,          /* Abort compaction now */
+        ISOLATE_NONE,           /* No pages isolated, continue scanning */
+        ISOLATE_SUCCESS,        /* Pages isolated, migrate */
+} isolate_migrate_t;
+
 /*
  * Isolate all pages that can be migrated from the block pointed to by
  * the migrate scanner within compact_control.
  */
-static unsigned long isolate_migratepages(struct zone *zone,
+static isolate_migrate_t isolate_migratepages(struct zone *zone,
                                         struct compact_control *cc)
 {
         unsigned long low_pfn, end_pfn;
@@ -272,7 +279,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
         /* Do not cross the free scanner or scan within a memory hole */
         if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
                 cc->migrate_pfn = end_pfn;
-                return 0;
+                return ISOLATE_NONE;
         }
 
         /*
@@ -281,10 +288,14 @@ static unsigned long isolate_migratepages(struct zone *zone,
          * delay for some time until fewer pages are isolated
          */
         while (unlikely(too_many_isolated(zone))) {
+                /* async migration should just abort */
+                if (!cc->sync)
+                        return ISOLATE_ABORT;
+
                 congestion_wait(BLK_RW_ASYNC, HZ/10);
 
                 if (fatal_signal_pending(current))
-                        return 0;
+                        return ISOLATE_ABORT;
         }
 
         /* Time to isolate some pages for migration */
@@ -369,7 +380,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
 
         trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
 
-        return cc->nr_migratepages;
+        return ISOLATE_SUCCESS;
 }
 
 /*
@@ -535,8 +546,15 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
                 unsigned long nr_migrate, nr_remaining;
                 int err;
 
-                if (!isolate_migratepages(zone, cc))
+                switch (isolate_migratepages(zone, cc)) {
+                case ISOLATE_ABORT:
+                        ret = COMPACT_PARTIAL;
+                        goto out;
+                case ISOLATE_NONE:
                         continue;
+                case ISOLATE_SUCCESS:
+                        ;
+                }
 
                 nr_migrate = cc->nr_migratepages;
                 err = migrate_pages(&cc->migratepages, compaction_alloc,
@@ -560,6 +578,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
 
         }
 
+out:
         /* Release free pages and check accounting */
         cc->nr_freepages -= release_freepages(&cc->freepages);
         VM_BUG_ON(cc->nr_freepages != 0);