4 files changed, 29 insertions, 2 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3ac040f19369..ca6ca92418a6 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -317,6 +317,12 @@ struct zone {
          */
         unsigned long           lowmem_reserve[MAX_NR_ZONES];
 
+        /*
+         * This is a per-zone reserve of pages that should not be
+         * considered dirtyable memory.
+         */
+        unsigned long           dirty_balance_reserve;
+
 #ifdef CONFIG_NUMA
         int node;
         /*
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 1e22e126d2ac..06061a7f8e69 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -207,6 +207,7 @@ struct swap_list_t {
 /* linux/mm/page_alloc.c */
 extern unsigned long totalram_pages;
 extern unsigned long totalreserve_pages;
+extern unsigned long dirty_balance_reserve;
 extern unsigned int nr_free_buffer_pages(void);
 extern unsigned int nr_free_pagecache_pages(void);
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c081bf62202b..9ab6de82d8e6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -157,7 +157,7 @@ static unsigned long highmem_dirtyable_memory(unsigned long total)
                         &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
 
                 x += zone_page_state(z, NR_FREE_PAGES) +
-                     zone_reclaimable_pages(z);
+                     zone_reclaimable_pages(z) - z->dirty_balance_reserve;
         }
         /*
          * Make sure that the number of highmem pages is never larger
@@ -181,7 +181,8 @@ static unsigned long determine_dirtyable_memory(void)
 {
         unsigned long x;
 
-        x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
+        x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages() -
+            dirty_balance_reserve;
 
         if (!vm_highmem_is_dirtyable)
                 x -= highmem_dirtyable_memory(x);
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;
 }