1 files changed, 19 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 93baebcc06f3..2cb9eb71e282 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -97,6 +97,14 @@ EXPORT_SYMBOL(node_states);
 
 unsigned long totalram_pages __read_mostly;
 unsigned long totalreserve_pages __read_mostly;
+/*
+ * When calculating the number of globally allowed dirty pages, there
+ * is a certain number of per-zone reserves that should not be
+ * considered dirtyable memory.  This is the sum of those reserves
+ * over all existing zones that contribute dirtyable memory.
+ */
+unsigned long dirty_balance_reserve __read_mostly;
+
 int percpu_pagelist_fraction;
 gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
 
@@ -4822,8 +4830,19 @@ static void calculate_totalreserve_pages(void)
                         if (max > zone->present_pages)
                                 max = zone->present_pages;
                         reserve_pages += max;
+                        /*
+                         * Lowmem reserves are not available to
+                         * GFP_HIGHUSER page cache allocations and
+                         * kswapd tries to balance zones to their high
+                         * watermark.  As a result, neither should be
+                         * regarded as dirtyable memory, to prevent a
+                         * situation where reclaim has to clean pages
+                         * in order to balance the zones.
+                         */
+                        zone->dirty_balance_reserve = max;
                 }
         }
+        dirty_balance_reserve = reserve_pages;
         totalreserve_pages = reserve_pages;
 }