1 files changed, 86 insertions, 16 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 4d4074cff300..b493db7841dc 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -69,6 +69,12 @@ static inline long sync_writeback_pages(void)
 int dirty_background_ratio = 5;
 
 /*
+ * dirty_background_bytes starts at 0 (disabled) so that it is a function of
+ * dirty_background_ratio * the amount of dirtyable memory
+ */
+unsigned long dirty_background_bytes;
+
+/*
  * free highmem will not be subtracted from the total free memory
  * for calculating free ratios if vm_highmem_is_dirtyable is true
  */
@@ -80,6 +86,12 @@ int vm_highmem_is_dirtyable;
 int vm_dirty_ratio = 10;
 
 /*
+ * vm_dirty_bytes starts at 0 (disabled) so that it is a function of
+ * vm_dirty_ratio * the amount of dirtyable memory
+ */
+unsigned long vm_dirty_bytes;
+
+/*
  * The interval between `kupdate'-style writebacks, in jiffies
  */
 int dirty_writeback_interval = 5 * HZ;
@@ -135,23 +147,75 @@ static int calc_period_shift(void)
 {
 	unsigned long dirty_total;
 
-	dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / 100;
+	if (vm_dirty_bytes)
+		dirty_total = vm_dirty_bytes / PAGE_SIZE;
+	else
+		dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
+				100;
 	return 2 + ilog2(dirty_total - 1);
 }
 
 /*
- * update the period when the dirty ratio changes.
+ * update the period when the dirty threshold changes.
  */
+static void update_completion_period(void)
+{
+	int shift = calc_period_shift();
+	prop_change_shift(&vm_completions, shift);
+	prop_change_shift(&vm_dirties, shift);
+}
+
+int dirty_background_ratio_handler(struct ctl_table *table, int write,
+		struct file *filp, void __user *buffer, size_t *lenp,
+		loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+	if (ret == 0 && write)
+		dirty_background_bytes = 0;
+	return ret;
+}
+
+int dirty_background_bytes_handler(struct ctl_table *table, int write,
+		struct file *filp, void __user *buffer, size_t *lenp,
+		loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
+	if (ret == 0 && write)
+		dirty_background_ratio = 0;
+	return ret;
+}
+
 int dirty_ratio_handler(struct ctl_table *table, int write,
 		struct file *filp, void __user *buffer, size_t *lenp,
 		loff_t *ppos)
 {
 	int old_ratio = vm_dirty_ratio;
-	int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
 	if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
-		int shift = calc_period_shift();
-		prop_change_shift(&vm_completions, shift);
-		prop_change_shift(&vm_dirties, shift);
+		update_completion_period();
+		vm_dirty_bytes = 0;
+	}
+	return ret;
+}
+
+
+int dirty_bytes_handler(struct ctl_table *table, int write,
+		struct file *filp, void __user *buffer, size_t *lenp,
+		loff_t *ppos)
+{
+	int old_bytes = vm_dirty_bytes;
+	int ret;
+
+	ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
+	if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
+		update_completion_period();
+		vm_dirty_ratio = 0;
 	}
 	return ret;
 }
@@ -365,23 +429,29 @@ void
 get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty,
 		 unsigned long *pbdi_dirty, struct backing_dev_info *bdi)
 {
-	int background_ratio;		/* Percentages */
-	int dirty_ratio;
 	unsigned long background;
 	unsigned long dirty;
 	unsigned long available_memory = determine_dirtyable_memory();
 	struct task_struct *tsk;
 
-	dirty_ratio = vm_dirty_ratio;
-	if (dirty_ratio < 5)
-		dirty_ratio = 5;
+	if (vm_dirty_bytes)
+		dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
+	else {
+		int dirty_ratio;
 
-	background_ratio = dirty_background_ratio;
-	if (background_ratio >= dirty_ratio)
-		background_ratio = dirty_ratio / 2;
+		dirty_ratio = vm_dirty_ratio;
+		if (dirty_ratio < 5)
+			dirty_ratio = 5;
+		dirty = (dirty_ratio * available_memory) / 100;
+	}
+
+	if (dirty_background_bytes)
+		background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
+	else
+		background = (dirty_background_ratio * available_memory) / 100;
 
-	background = (background_ratio * available_memory) / 100;
-	dirty = (dirty_ratio * available_memory) / 100;
+	if (background >= dirty)
+		background = dirty / 2;
 	tsk = current;
 	if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
 		background += background / 4;