Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs...

[sfrench/cifs-2.6.git] / mm / compaction.c

diff --git a/mm/compaction.c b/mm/compaction.c
index 94bdbe1f7caf85ca6e48cccc57b30e9253501fc6..6cc604bd56496e2742e371d63234af08f9f0859b 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -144,9 +144,20 @@ static void isolate_freepages(struct zone *zone,
        int nr_freepages = cc->nr_freepages;
        struct list_head *freelist = &cc->freepages;
 
+       /*
+        * Initialise the free scanner. The starting point is where we last
+        * scanned from (or the end of the zone if starting). The low point
+        * is the end of the pageblock the migration scanner is using.
+        */
        pfn = cc->free_pfn;
        low_pfn = cc->migrate_pfn + pageblock_nr_pages;
-       high_pfn = low_pfn;
+
+       /*
+        * Take care that if the migration scanner is at the end of the zone
+        * that the free scanner does not accidentally move to the next zone
+        * in the next isolation cycle.
+        */
+       high_pfn = min(low_pfn, pfn);
 
        /*
         * Isolate free pages until enough are available to migrate the
@@ -240,11 +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;
@@ -261,7 +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;
        }
 
        /*
@@ -270,10 +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 */
@@ -358,7 +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;
 }
 
 /*
@@ -480,7 +502,8 @@ unsigned long compaction_suitable(struct zone *zone, int order)
         * fragmentation index determines if allocation failures are due to
         * low memory or external fragmentation
         *
-        * index of -1 implies allocations might succeed dependingon watermarks
+        * index of -1000 implies allocations might succeed depending on
+        * watermarks
         * index towards 0 implies failure is due to lack of memory
         * index towards 1000 implies failure is due to fragmentation
         *
@@ -490,7 +513,8 @@ unsigned long compaction_suitable(struct zone *zone, int order)
        if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
                return COMPACT_SKIPPED;
 
-       if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0))
+       if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
+           0, 0))
                return COMPACT_PARTIAL;
 
        return COMPACT_CONTINUE;
@@ -522,8 +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,
@@ -547,6 +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);