1 files changed, 20 insertions, 23 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2a6978a07d56..f406e6fbaaa5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2598,38 +2598,35 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 }
 
 /*
- * Returns true if compaction should go ahead for a high-order request, or
- * the high-order allocation would succeed without compaction.
+ * Returns true if compaction should go ahead for a costly-order request, or
+ * the allocation would already succeed without compaction. Return false if we
+ * should reclaim first.
  */
 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
 {
         unsigned long watermark;
-        bool watermark_ok;
+        enum compact_result suitable;
 
-        /*
-         * Compaction takes time to run and there are potentially other
-         * callers using the pages just freed. Continue reclaiming until
-         * there is a buffer of free pages available to give compaction
-         * a reasonable chance of completing and allocating the page
-         */
-        watermark = high_wmark_pages(zone) + compact_gap(sc->order);
-        watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
-
-        /*
-         * If compaction is deferred, reclaim up to a point where
-         * compaction will have a chance of success when re-enabled
-         */
-        if (compaction_deferred(zone, sc->order))
-                return watermark_ok;
+        suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx);
+        if (suitable == COMPACT_SUCCESS)
+                /* Allocation should succeed already. Don't reclaim. */
+                return true;
+        if (suitable == COMPACT_SKIPPED)
+                /* Compaction cannot yet proceed. Do reclaim. */
+                return false;
 
         /*
-         * If compaction is not ready to start and allocation is not likely
-         * to succeed without it, then keep reclaiming.
+         * Compaction is already possible, but it takes time to run and there
+         * are potentially other callers using the pages just freed. So proceed
+         * with reclaim to make a buffer of free pages available to give
+         * compaction a reasonable chance of completing and allocating the page.
+         * Note that we won't actually reclaim the whole buffer in one attempt
+         * as the target watermark in should_continue_reclaim() is lower. But if
+         * we are already above the high+gap watermark, don't reclaim at all.
          */
-        if (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx) == COMPACT_SKIPPED)
-                return false;
+        watermark = high_wmark_pages(zone) + compact_gap(sc->order);
 
-        return watermark_ok;
+        return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
 }
 
 /*