mm: vmscan: scan until it finds eligible pages

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

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2f45c0520f43fbcb5696063172cd281553302f9d..8ad39bbc79e67eaff24c42201ae2470ffc21d0a7 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1449,7 +1449,7 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,
  *
  * Appropriate locks must be held before calling this function.
  *
- * @nr_to_scan:        The number of pages to look through on the list.
+ * @nr_to_scan:        The number of eligible pages to look through on the list.
  * @lruvec:    The LRU vector to pull pages from.
  * @dst:       The temp list to put pages on to.
  * @nr_scanned:        The number of pages that were scanned.
@@ -1469,11 +1469,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
        unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
        unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
        unsigned long skipped = 0;
-       unsigned long scan, nr_pages;
+       unsigned long scan, total_scan, nr_pages;
        LIST_HEAD(pages_skipped);
 
-       for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan &&
-                                       !list_empty(src); scan++) {
+       scan = 0;
+       for (total_scan = 0;
+            scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src);
+            total_scan++) {
                struct page *page;
 
                page = lru_to_page(src);
@@ -1487,6 +1489,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
                        continue;
                }
 
+               /*
+                * Do not count skipped pages because that makes the function
+                * return with no isolated pages if the LRU mostly contains
+                * ineligible pages.  This causes the VM to not reclaim any
+                * pages, triggering a premature OOM.
+                */
+               scan++;
                switch (__isolate_lru_page(page, mode)) {
                case 0:
                        nr_pages = hpage_nr_pages(page);
@@ -1524,9 +1533,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
                        skipped += nr_skipped[zid];
                }
        }
-       *nr_scanned = scan;
+       *nr_scanned = total_scan;
        trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
-                                   scan, skipped, nr_taken, mode, lru);
+                                   total_scan, skipped, nr_taken, mode, lru);
        update_lru_sizes(lruvec, lru, nr_zone_taken);
        return nr_taken;
 }