ath6kl: add tracing point for hif irqs

[cascardo/linux.git] / mm / page-writeback.c

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 6f42712..0713bfb 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -200,6 +200,18 @@ static unsigned long highmem_dirtyable_memory(unsigned long total)
                x += zone_page_state(z, NR_FREE_PAGES) +
                     zone_reclaimable_pages(z) - z->dirty_balance_reserve;
        }
+       /*
+        * Unreclaimable memory (kernel memory or anonymous memory
+        * without swap) can bring down the dirtyable pages below
+        * the zone's dirty balance reserve and the above calculation
+        * will underflow.  However we still want to add in nodes
+        * which are below threshold (negative values) to get a more
+        * accurate calculation but make sure that the total never
+        * underflows.
+        */
+       if ((long)x < 0)
+               x = 0;
+
        /*
         * Make sure that the number of highmem pages is never larger
         * than the number of the total dirtyable memory. This can only
@@ -222,8 +234,8 @@ static unsigned long global_dirtyable_memory(void)
 {
        unsigned long x;
 
-       x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages() -
-           dirty_balance_reserve;
+       x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
+       x -= min(x, dirty_balance_reserve);
 
        if (!vm_highmem_is_dirtyable)
                x -= highmem_dirtyable_memory(x);
@@ -290,9 +302,12 @@ static unsigned long zone_dirtyable_memory(struct zone *zone)
         * highmem zone can hold its share of dirty pages, so we don't
         * care about vm_highmem_is_dirtyable here.
         */
-       return zone_page_state(zone, NR_FREE_PAGES) +
-              zone_reclaimable_pages(zone) -
-              zone->dirty_balance_reserve;
+       unsigned long nr_pages = zone_page_state(zone, NR_FREE_PAGES) +
+               zone_reclaimable_pages(zone);
+
+       /* don't allow this to underflow */
+       nr_pages -= min(nr_pages, zone->dirty_balance_reserve);
+       return nr_pages;
 }
 
 /**