1 files changed, 8 insertions, 76 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ac644fe85589..3886b0bd7869 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3417,66 +3417,12 @@ void scan_mapping_unevictable_pages(struct address_space *mapping)
 
 }
 
-/**
- * scan_zone_unevictable_pages - check unevictable list for evictable pages
- * @zone - zone of which to scan the unevictable list
- *
- * Scan @zone's unevictable LRU lists to check for pages that have become
- * evictable.  Move those that have to @zone's inactive list where they
- * become candidates for reclaim, unless shrink_inactive_zone() decides
- * to reactivate them.  Pages that are still unevictable are rotated
- * back onto @zone's unevictable list.
- */
-#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
-static void scan_zone_unevictable_pages(struct zone *zone)
+static void warn_scan_unevictable_pages(void)
 {
-        struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
-        unsigned long scan;
-        unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
-
-        while (nr_to_scan > 0) {
-                unsigned long batch_size = min(nr_to_scan,
-                                                SCAN_UNEVICTABLE_BATCH_SIZE);
-
-                spin_lock_irq(&zone->lru_lock);
-                for (scan = 0;  scan < batch_size; scan++) {
-                        struct page *page = lru_to_page(l_unevictable);
-
-                        if (!trylock_page(page))
-                                continue;
-
-                        prefetchw_prev_lru_page(page, l_unevictable, flags);
-
-                        if (likely(PageLRU(page) && PageUnevictable(page)))
-                                check_move_unevictable_page(page, zone);
-
-                        unlock_page(page);
-                }
-                spin_unlock_irq(&zone->lru_lock);
-
-                nr_to_scan -= batch_size;
-        }
-}
-
-
-/**
- * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
- *
- * A really big hammer:  scan all zones' unevictable LRU lists to check for
- * pages that have become evictable.  Move those back to the zones'
- * inactive list where they become candidates for reclaim.
- * This occurs when, e.g., we have unswappable pages on the unevictable lists,
- * and we add swap to the system.  As such, it runs in the context of a task
- * that has possibly/probably made some previously unevictable pages
- * evictable.
- */
-static void scan_all_zones_unevictable_pages(void)
-{
-        struct zone *zone;
-
-        for_each_zone(zone) {
-                scan_zone_unevictable_pages(zone);
-        }
+        printk_once(KERN_WARNING
+                    "The scan_unevictable_pages sysctl/node-interface has been "
+                    "disabled for lack of a legitimate use case.  If you have "
+                    "one, please send an email to linux-mm@kvack.org.\n");
 }
 
 /*
@@ -3489,11 +3435,8 @@ int scan_unevictable_handler(struct ctl_table *table, int write,
                            void __user *buffer,
                            size_t *length, loff_t *ppos)
 {
+        warn_scan_unevictable_pages();
         proc_doulongvec_minmax(table, write, buffer, length, ppos);
-
-        if (write && *(unsigned long *)table->data)
-                scan_all_zones_unevictable_pages();
-
         scan_unevictable_pages = 0;
         return 0;
 }
@@ -3508,6 +3451,7 @@ static ssize_t read_scan_unevictable_node(struct sys_device *dev,
                                           struct sysdev_attribute *attr,
                                           char *buf)
 {
+        warn_scan_unevictable_pages();
         return sprintf(buf, "0\n");     /* always zero; should fit... */
 }
 
@@ -3515,19 +3459,7 @@ static ssize_t write_scan_unevictable_node(struct sys_device *dev,
                                            struct sysdev_attribute *attr,
                                         const char *buf, size_t count)
 {
-        struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
-        struct zone *zone;
-        unsigned long res;
-        unsigned long req = strict_strtoul(buf, 10, &res);
-
-        if (req || !res)
-                return 1; /* Invalid input or zero is no-op */
-
-        for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
-                if (!populated_zone(zone))
-                        continue;
-                scan_zone_unevictable_pages(zone);
-        }
+        warn_scan_unevictable_pages();
         return 1;
 }