mm/page-writeback.c: make determine_dirtyable_memory static again

The tracing ring-buffer used this function briefly, but not anymore.
Make it local to the writeback code again.

Also, move the function so that no forward declaration needs to be
reintroduced.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 60 insertions, 62 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 8616ef3025a4..c081bf62202b 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -130,6 +130,66 @@ unsigned long global_dirty_limit;
 static struct prop_descriptor vm_completions;
 
 /*
+ * Work out the current dirty-memory clamping and background writeout
+ * thresholds.
+ *
+ * The main aim here is to lower them aggressively if there is a lot of mapped
+ * memory around.  To avoid stressing page reclaim with lots of unreclaimable
+ * pages.  It is better to clamp down on writers than to start swapping, and
+ * performing lots of scanning.
+ *
+ * We only allow 1/2 of the currently-unmapped memory to be dirtied.
+ *
+ * We don't permit the clamping level to fall below 5% - that is getting rather
+ * excessive.
+ *
+ * We make sure that the background writeout level is below the adjusted
+ * clamping level.
+ */
+static unsigned long highmem_dirtyable_memory(unsigned long total)
+{
+#ifdef CONFIG_HIGHMEM
+        int node;
+        unsigned long x = 0;
+
+        for_each_node_state(node, N_HIGH_MEMORY) {
+                struct zone *z =
+                        &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
+
+                x += zone_page_state(z, NR_FREE_PAGES) +
+                     zone_reclaimable_pages(z);
+        }
+        /*
+         * Make sure that the number of highmem pages is never larger
+         * than the number of the total dirtyable memory. This can only
+         * occur in very strange VM situations but we want to make sure
+         * that this does not occur.
+         */
+        return min(x, total);
+#else
+        return 0;
+#endif
+}
+
+/**
+ * determine_dirtyable_memory - amount of memory that may be used
+ *
+ * Returns the numebr of pages that can currently be freed and used
+ * by the kernel for direct mappings.
+ */
+static unsigned long determine_dirtyable_memory(void)
+{
+        unsigned long x;
+
+        x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
+
+        if (!vm_highmem_is_dirtyable)
+                x -= highmem_dirtyable_memory(x);
+
+        return x + 1;   /* Ensure that we never return 0 */
+}
+
+/*
  * couple the period to the dirty_ratio:
  *
  *   period/2 ~ roundup_pow_of_two(dirty limit)
@@ -196,7 +256,6 @@ int dirty_ratio_handler(struct ctl_table *table, int write,
         return ret;
 }
 
-
 int dirty_bytes_handler(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp,
                 loff_t *ppos)
@@ -291,67 +350,6 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
 }
 EXPORT_SYMBOL(bdi_set_max_ratio);
 
-/*
- * Work out the current dirty-memory clamping and background writeout
- * thresholds.
- *
- * The main aim here is to lower them aggressively if there is a lot of mapped
- * memory around.  To avoid stressing page reclaim with lots of unreclaimable
- * pages.  It is better to clamp down on writers than to start swapping, and
- * performing lots of scanning.
- *
- * We only allow 1/2 of the currently-unmapped memory to be dirtied.
- *
- * We don't permit the clamping level to fall below 5% - that is getting rather
- * excessive.
- *
- * We make sure that the background writeout level is below the adjusted
- * clamping level.
- */
-
-static unsigned long highmem_dirtyable_memory(unsigned long total)
-{
-#ifdef CONFIG_HIGHMEM
-        int node;
-        unsigned long x = 0;
-
-        for_each_node_state(node, N_HIGH_MEMORY) {
-                struct zone *z =
-                        &NODE_DATA(node)->node_zones[ZONE_HIGHMEM];
-
-                x += zone_page_state(z, NR_FREE_PAGES) +
-                     zone_reclaimable_pages(z);
-        }
-        /*
-         * Make sure that the number of highmem pages is never larger
-         * than the number of the total dirtyable memory. This can only
-         * occur in very strange VM situations but we want to make sure
-         * that this does not occur.
-         */
-        return min(x, total);
-#else
-        return 0;
-#endif
-}
-
-/**
- * determine_dirtyable_memory - amount of memory that may be used
- *
- * Returns the numebr of pages that can currently be freed and used
- * by the kernel for direct mappings.
- */
-unsigned long determine_dirtyable_memory(void)
-{
-        unsigned long x;
-
-        x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages();
-
-        if (!vm_highmem_is_dirtyable)
-                x -= highmem_dirtyable_memory(x);
-
-        return x + 1;   /* Ensure that we never return 0 */
-}
-
 static unsigned long dirty_freerun_ceiling(unsigned long thresh,
                                            unsigned long bg_thresh)
 {