vmscan: abort reclaim/compaction if compaction can proceed

[firefly-linux-kernel-4.4.55.git] / mm / compaction.c

diff --git a/mm/compaction.c b/mm/compaction.c
index 6cc604bd56496e2742e371d63234af08f9f0859b..adc5336ad8444c757f2c6b59567841180fffe940 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -320,12 +320,34 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
                } else if (!locked)
                        spin_lock_irq(&zone->lru_lock);
 
+               /*
+                * migrate_pfn does not necessarily start aligned to a
+                * pageblock. Ensure that pfn_valid is called when moving
+                * into a new MAX_ORDER_NR_PAGES range in case of large
+                * memory holes within the zone
+                */
+               if ((low_pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) {
+                       if (!pfn_valid(low_pfn)) {
+                               low_pfn += MAX_ORDER_NR_PAGES - 1;
+                               continue;
+                       }
+               }
+
                if (!pfn_valid_within(low_pfn))
                        continue;
                nr_scanned++;
 
-               /* Get the page and skip if free */
+               /*
+                * Get the page and ensure the page is within the same zone.
+                * See the comment in isolate_freepages about overlapping
+                * nodes. It is deliberate that the new zone lock is not taken
+                * as memory compaction should not move pages between nodes.
+                */
                page = pfn_to_page(low_pfn);
+               if (page_zone(page) != zone)
+                       continue;
+
+               /* Skip if free */
                if (PageBuddy(page))
                        continue;
 
@@ -574,8 +596,11 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
                if (err) {
                        putback_lru_pages(&cc->migratepages);
                        cc->nr_migratepages = 0;
+                       if (err == -ENOMEM) {
+                               ret = COMPACT_PARTIAL;
+                               goto out;
+                       }
                }
-
        }
 
 out: