1 files changed, 29 insertions, 13 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 87e4d6a6dc11..ae3bf0a09cdd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1642,18 +1642,6 @@ static void move_active_pages_to_lru(struct zone *zone,
         unsigned long pgmoved = 0;
         struct page *page;
 
-        if (buffer_heads_over_limit) {
-                spin_unlock_irq(&zone->lru_lock);
-                list_for_each_entry(page, list, lru) {
-                        if (page_has_private(page) && trylock_page(page)) {
-                                if (page_has_private(page))
-                                        try_to_release_page(page, 0);
-                                unlock_page(page);
-                        }
-                }
-                spin_lock_irq(&zone->lru_lock);
-        }
-
         while (!list_empty(list)) {
                 struct lruvec *lruvec;
 
@@ -1735,6 +1723,14 @@ static void shrink_active_list(unsigned long nr_to_scan,
                         continue;
                 }
 
+                if (unlikely(buffer_heads_over_limit)) {
+                        if (page_has_private(page) && trylock_page(page)) {
+                                if (page_has_private(page))
+                                        try_to_release_page(page, 0);
+                                unlock_page(page);
+                        }
+                }
+
                 if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
                         nr_rotated += hpage_nr_pages(page);
                         /*
@@ -2238,6 +2234,14 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
         unsigned long nr_soft_scanned;
         bool aborted_reclaim = false;
 
+        /*
+         * If the number of buffer_heads in the machine exceeds the maximum
+         * allowed level, force direct reclaim to scan the highmem zone as
+         * highmem pages could be pinning lowmem pages storing buffer_heads
+         */
+        if (buffer_heads_over_limit)
+                sc->gfp_mask |= __GFP_HIGHMEM;
+
         for_each_zone_zonelist_nodemask(zone, z, zonelist,
                                         gfp_zone(sc->gfp_mask), sc->nodemask) {
                 if (!populated_zone(zone))
@@ -2727,6 +2731,17 @@ loop_again:
                          */
                         age_active_anon(zone, &sc, priority);
 
+                        /*
+                         * If the number of buffer_heads in the machine
+                         * exceeds the maximum allowed level and this node
+                         * has a highmem zone, force kswapd to reclaim from
+                         * it to relieve lowmem pressure.
+                         */
+                        if (buffer_heads_over_limit && is_highmem_idx(i)) {
+                                end_zone = i;
+                                break;
+                        }
+
                         if (!zone_watermark_ok_safe(zone, order,
                                         high_wmark_pages(zone), 0, 0)) {
                                 end_zone = i;
@@ -2802,7 +2817,8 @@ loop_again:
                                                 COMPACT_SKIPPED)
                                 testorder = 0;
 
-                        if (!zone_watermark_ok_safe(zone, testorder,
+                        if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
+                                    !zone_watermark_ok_safe(zone, order,
                                         high_wmark_pages(zone) + balance_gap,
                                         end_zone, 0)) {
                                 shrink_zone(priority, zone, &sc);