CHROMIUM: vmscan: add min_filelist_kbytes sysctl for protecting the working set

mm/vmscan.c

Index: mm/vmscan.c
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4649929401f888e87814ae35d87a106a9db410ae..045e8299b4ace3e3694e09c9fea32c8b09b40fb1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -130,6 +130,11 @@ struct scan_control {
 int vm_swappiness = 60;
 long vm_total_pages;	/* The total number of pages which the VM controls */
 
+/*
+ * Low watermark used to prevent fscache thrashing during low memory.
+ */
+int min_filelist_kbytes = 0;
+
 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
 
@@ -1510,11 +1515,31 @@ static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
 		return inactive_anon_is_low(zone, sc);
 }
 
+/*
+ * Check low watermark used to prevent fscache thrashing during low memory.
+ */
+static int file_is_low(struct zone *zone, struct scan_control *sc)
+{
+	unsigned long pages_min, active, inactive;
+
+	if (!scanning_global_lru(sc))
+		return false;
+
+	pages_min = min_filelist_kbytes >> (PAGE_SHIFT - 10);
+	active = zone_page_state(zone, NR_ACTIVE_FILE);
+	inactive = zone_page_state(zone, NR_INACTIVE_FILE);
+
+	return ((active + inactive) < pages_min);
+}
+
 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
 	struct zone *zone, struct scan_control *sc, int priority)
 {
 	int file = is_file_lru(lru);
 
+	if (file && file_is_low(zone, sc))
+		return 0;
+
 	if (is_active_lru(lru)) {
 		if (inactive_list_is_low(zone, sc, file))
 		    shrink_active_list(nr_to_scan, zone, sc, priority, file);