Merge branch 'akpm' (Andrew's incoming)

Quoth Andrew:

 - Most of MM.  Still waiting for the poweroc guys to get off their
   butts and review some threaded hugepages patches.

 - alpha

 - vfs bits

 - drivers/misc

 - a few core kerenl tweaks

 - printk() features

 - MAINTAINERS updates

 - backlight merge

 - leds merge

 - various lib/ updates

 - checkpatch updates

* akpm: (127 commits)
  epoll: fix spurious lockdep warnings
  checkpatch: add a --strict check for utf-8 in commit logs
  kernel.h/checkpatch: mark strict_strto<foo> and simple_strto<foo> as obsolete
  llist-return-whether-list-is-empty-before-adding-in-llist_add-fix
  wireless: at76c50x: follow rename pack_hex_byte to hex_byte_pack
  fat: follow rename pack_hex_byte() to hex_byte_pack()
  security: follow rename pack_hex_byte() to hex_byte_pack()
  kgdb: follow rename pack_hex_byte() to hex_byte_pack()
  lib: rename pack_hex_byte() to hex_byte_pack()
  lib/string.c: fix strim() semantics for strings that have only blanks
  lib/idr.c: fix comment for ida_get_new_above()
  lib/percpu_counter.c: enclose hotplug only variables in hotplug ifdef
  lib/bitmap.c: quiet sparse noise about address space
  lib/spinlock_debug.c: print owner on spinlock lockup
  lib/kstrtox: common code between kstrto*() and simple_strto*() functions
  drivers/leds/leds-lp5521.c: check if reset is successful
  leds: turn the blink_timer off before starting to blink
  leds: save the delay values after a successful call to blink_set()
  drivers/leds/leds-gpio.c: use gpio_get_value_cansleep() when initializing
  drivers/leds/leds-lm3530.c: add __devexit_p where needed
  ...

1 files changed, 177 insertions, 148 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9fdfce7ba40..a90c603a8d0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -495,15 +495,6 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
 			return PAGE_ACTIVATE;
 		}
 
-		/*
-		 * Wait on writeback if requested to. This happens when
-		 * direct reclaiming a large contiguous area and the
-		 * first attempt to free a range of pages fails.
-		 */
-		if (PageWriteback(page) &&
-		    (sc->reclaim_mode & RECLAIM_MODE_SYNC))
-			wait_on_page_writeback(page);
-
 		if (!PageWriteback(page)) {
 			/* synchronous write or broken a_ops? */
 			ClearPageReclaim(page);
@@ -642,13 +633,14 @@ redo:
 		lru = LRU_UNEVICTABLE;
 		add_page_to_unevictable_list(page);
 		/*
-		 * When racing with an mlock clearing (page is
-		 * unlocked), make sure that if the other thread does
-		 * not observe our setting of PG_lru and fails
-		 * isolation, we see PG_mlocked cleared below and move
+		 * When racing with an mlock or AS_UNEVICTABLE clearing
+		 * (page is unlocked) make sure that if the other thread
+		 * does not observe our setting of PG_lru and fails
+		 * isolation/check_move_unevictable_page,
+		 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
 		 * the page back to the evictable list.
 		 *
-		 * The other side is TestClearPageMlocked().
+		 * The other side is TestClearPageMlocked() or shmem_lock().
 		 */
 		smp_mb();
 	}
@@ -759,7 +751,10 @@ static noinline_for_stack void free_page_list(struct list_head *free_pages)
  */
 static unsigned long shrink_page_list(struct list_head *page_list,
 				      struct zone *zone,
-				      struct scan_control *sc)
+				      struct scan_control *sc,
+				      int priority,
+				      unsigned long *ret_nr_dirty,
+				      unsigned long *ret_nr_writeback)
 {
 	LIST_HEAD(ret_pages);
 	LIST_HEAD(free_pages);
@@ -767,6 +762,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 	unsigned long nr_dirty = 0;
 	unsigned long nr_congested = 0;
 	unsigned long nr_reclaimed = 0;
+	unsigned long nr_writeback = 0;
 
 	cond_resched();
 
@@ -803,13 +799,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
 
 		if (PageWriteback(page)) {
+			nr_writeback++;
 			/*
-			 * Synchronous reclaim is performed in two passes,
-			 * first an asynchronous pass over the list to
-			 * start parallel writeback, and a second synchronous
-			 * pass to wait for the IO to complete.  Wait here
-			 * for any page for which writeback has already
-			 * started.
+			 * Synchronous reclaim cannot queue pages for
+			 * writeback due to the possibility of stack overflow
+			 * but if it encounters a page under writeback, wait
+			 * for the IO to complete.
 			 */
 			if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
 			    may_enter_fs)
@@ -865,6 +860,25 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		if (PageDirty(page)) {
 			nr_dirty++;
 
+			/*
+			 * Only kswapd can writeback filesystem pages to
+			 * avoid risk of stack overflow but do not writeback
+			 * unless under significant pressure.
+			 */
+			if (page_is_file_cache(page) &&
+					(!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
+				/*
+				 * Immediately reclaim when written back.
+				 * Similar in principal to deactivate_page()
+				 * except we already have the page isolated
+				 * and know it's dirty
+				 */
+				inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
+				SetPageReclaim(page);
+
+				goto keep_locked;
+			}
+
 			if (references == PAGEREF_RECLAIM_CLEAN)
 				goto keep_locked;
 			if (!may_enter_fs)
@@ -999,6 +1013,8 @@ keep_lumpy:
 
 	list_splice(&ret_pages, page_list);
 	count_vm_events(PGACTIVATE, pgactivate);
+	*ret_nr_dirty += nr_dirty;
+	*ret_nr_writeback += nr_writeback;
 	return nr_reclaimed;
 }
 
@@ -1012,23 +1028,27 @@ keep_lumpy:
  *
  * returns 0 on success, -ve errno on failure.
  */
-int __isolate_lru_page(struct page *page, int mode, int file)
+int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
 {
+	bool all_lru_mode;
 	int ret = -EINVAL;
 
 	/* Only take pages on the LRU. */
 	if (!PageLRU(page))
 		return ret;
 
+	all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
+		(ISOLATE_ACTIVE|ISOLATE_INACTIVE);
+
 	/*
 	 * When checking the active state, we need to be sure we are
 	 * dealing with comparible boolean values.  Take the logical not
 	 * of each.
 	 */
-	if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
+	if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
 		return ret;
 
-	if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
+	if (!all_lru_mode && !!page_is_file_cache(page) != file)
 		return ret;
 
 	/*
@@ -1041,6 +1061,12 @@ int __isolate_lru_page(struct page *page, int mode, int file)
 
 	ret = -EBUSY;
 
+	if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
+		return ret;
+
+	if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
+		return ret;
+
 	if (likely(get_page_unless_zero(page))) {
 		/*
 		 * Be careful not to clear PageLRU until after we're
@@ -1076,7 +1102,8 @@ int __isolate_lru_page(struct page *page, int mode, int file)
  */
 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 		struct list_head *src, struct list_head *dst,
-		unsigned long *scanned, int order, int mode, int file)
+		unsigned long *scanned, int order, isolate_mode_t mode,
+		int file)
 {
 	unsigned long nr_taken = 0;
 	unsigned long nr_lumpy_taken = 0;
@@ -1201,8 +1228,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 static unsigned long isolate_pages_global(unsigned long nr,
 					struct list_head *dst,
 					unsigned long *scanned, int order,
-					int mode, struct zone *z,
-					int active, int file)
+					isolate_mode_t mode,
+					struct zone *z,	int active, int file)
 {
 	int lru = LRU_BASE;
 	if (active)
@@ -1394,7 +1421,7 @@ static noinline_for_stack void update_isolated_counts(struct zone *zone,
 }
 
 /*
- * Returns true if the caller should wait to clean dirty/writeback pages.
+ * Returns true if a direct reclaim should wait on pages under writeback.
  *
  * If we are direct reclaiming for contiguous pages and we do not reclaim
  * everything in the list, try again and wait for writeback IO to complete.
@@ -1448,6 +1475,9 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 	unsigned long nr_taken;
 	unsigned long nr_anon;
 	unsigned long nr_file;
+	unsigned long nr_dirty = 0;
+	unsigned long nr_writeback = 0;
+	isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
 
 	while (unlikely(too_many_isolated(zone, file, sc))) {
 		congestion_wait(BLK_RW_ASYNC, HZ/10);
@@ -1458,15 +1488,21 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 	}
 
 	set_reclaim_mode(priority, sc, false);
+	if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
+		reclaim_mode |= ISOLATE_ACTIVE;
+
 	lru_add_drain();
+
+	if (!sc->may_unmap)
+		reclaim_mode |= ISOLATE_UNMAPPED;
+	if (!sc->may_writepage)
+		reclaim_mode |= ISOLATE_CLEAN;
+
 	spin_lock_irq(&zone->lru_lock);
 
 	if (scanning_global_lru(sc)) {
-		nr_taken = isolate_pages_global(nr_to_scan,
-			&page_list, &nr_scanned, sc->order,
-			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
-					ISOLATE_BOTH : ISOLATE_INACTIVE,
-			zone, 0, file);
+		nr_taken = isolate_pages_global(nr_to_scan, &page_list,
+			&nr_scanned, sc->order, reclaim_mode, zone, 0, file);
 		zone->pages_scanned += nr_scanned;
 		if (current_is_kswapd())
 			__count_zone_vm_events(PGSCAN_KSWAPD, zone,
@@ -1475,12 +1511,9 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 			__count_zone_vm_events(PGSCAN_DIRECT, zone,
 					       nr_scanned);
 	} else {
-		nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
-			&page_list, &nr_scanned, sc->order,
-			sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
-					ISOLATE_BOTH : ISOLATE_INACTIVE,
-			zone, sc->mem_cgroup,
-			0, file);
+		nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
+			&nr_scanned, sc->order, reclaim_mode, zone,
+			sc->mem_cgroup, 0, file);
 		/*
 		 * mem_cgroup_isolate_pages() keeps track of
 		 * scanned pages on its own.
@@ -1496,12 +1529,14 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 
 	spin_unlock_irq(&zone->lru_lock);
 
-	nr_reclaimed = shrink_page_list(&page_list, zone, sc);
+	nr_reclaimed = shrink_page_list(&page_list, zone, sc, priority,
+						&nr_dirty, &nr_writeback);
 
 	/* Check if we should syncronously wait for writeback */
 	if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
 		set_reclaim_mode(priority, sc, true);
-		nr_reclaimed += shrink_page_list(&page_list, zone, sc);
+		nr_reclaimed += shrink_page_list(&page_list, zone, sc,
+					priority, &nr_dirty, &nr_writeback);
 	}
 
 	local_irq_disable();
@@ -1511,6 +1546,32 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 
 	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
 
+	/*
+	 * If reclaim is isolating dirty pages under writeback, it implies
+	 * that the long-lived page allocation rate is exceeding the page
+	 * laundering rate. Either the global limits are not being effective
+	 * at throttling processes due to the page distribution throughout
+	 * zones or there is heavy usage of a slow backing device. The
+	 * only option is to throttle from reclaim context which is not ideal
+	 * as there is no guarantee the dirtying process is throttled in the
+	 * same way balance_dirty_pages() manages.
+	 *
+	 * This scales the number of dirty pages that must be under writeback
+	 * before throttling depending on priority. It is a simple backoff
+	 * function that has the most effect in the range DEF_PRIORITY to
+	 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
+	 * in trouble and reclaim is considered to be in trouble.
+	 *
+	 * DEF_PRIORITY   100% isolated pages must be PageWriteback to throttle
+	 * DEF_PRIORITY-1  50% must be PageWriteback
+	 * DEF_PRIORITY-2  25% must be PageWriteback, kswapd in trouble
+	 * ...
+	 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
+	 *                     isolated page is PageWriteback
+	 */
+	if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
+		wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
+
 	trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
 		zone_idx(zone),
 		nr_scanned, nr_reclaimed,
@@ -1582,19 +1643,26 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
 	struct page *page;
 	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
 	unsigned long nr_rotated = 0;
+	isolate_mode_t reclaim_mode = ISOLATE_ACTIVE;
 
 	lru_add_drain();
+
+	if (!sc->may_unmap)
+		reclaim_mode |= ISOLATE_UNMAPPED;
+	if (!sc->may_writepage)
+		reclaim_mode |= ISOLATE_CLEAN;
+
 	spin_lock_irq(&zone->lru_lock);
 	if (scanning_global_lru(sc)) {
 		nr_taken = isolate_pages_global(nr_pages, &l_hold,
 						&pgscanned, sc->order,
-						ISOLATE_ACTIVE, zone,
+						reclaim_mode, zone,
 						1, file);
 		zone->pages_scanned += pgscanned;
 	} else {
 		nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
 						&pgscanned, sc->order,
-						ISOLATE_ACTIVE, zone,
+						reclaim_mode, zone,
 						sc->mem_cgroup, 1, file);
 		/*
 		 * mem_cgroup_isolate_pages() keeps track of
@@ -1795,12 +1863,19 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
 	enum lru_list l;
 	int noswap = 0;
 	bool force_scan = false;
-	unsigned long nr_force_scan[2];
 
-	/* kswapd does zone balancing and needs to scan this zone */
+	/*
+	 * If the zone or memcg is small, nr[l] can be 0.  This
+	 * results in no scanning on this priority and a potential
+	 * priority drop.  Global direct reclaim can go to the next
+	 * zone and tends to have no problems. Global kswapd is for
+	 * zone balancing and it needs to scan a minimum amount. When
+	 * reclaiming for a memcg, a priority drop can cause high
+	 * latencies, so it's better to scan a minimum amount there as
+	 * well.
+	 */
 	if (scanning_global_lru(sc) && current_is_kswapd())
 		force_scan = true;
-	/* memcg may have small limit and need to avoid priority drop */
 	if (!scanning_global_lru(sc))
 		force_scan = true;
 
@@ -1810,8 +1885,6 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
 		fraction[0] = 0;
 		fraction[1] = 1;
 		denominator = 1;
-		nr_force_scan[0] = 0;
-		nr_force_scan[1] = SWAP_CLUSTER_MAX;
 		goto out;
 	}
 
@@ -1828,8 +1901,6 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
 			fraction[0] = 1;
 			fraction[1] = 0;
 			denominator = 1;
-			nr_force_scan[0] = SWAP_CLUSTER_MAX;
-			nr_force_scan[1] = 0;
 			goto out;
 		}
 	}
@@ -1878,11 +1949,6 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
 	fraction[0] = ap;
 	fraction[1] = fp;
 	denominator = ap + fp + 1;
-	if (force_scan) {
-		unsigned long scan = SWAP_CLUSTER_MAX;
-		nr_force_scan[0] = div64_u64(scan * ap, denominator);
-		nr_force_scan[1] = div64_u64(scan * fp, denominator);
-	}
 out:
 	for_each_evictable_lru(l) {
 		int file = is_file_lru(l);
@@ -1891,20 +1957,10 @@ out:
 		scan = zone_nr_lru_pages(zone, sc, l);
 		if (priority || noswap) {
 			scan >>= priority;
+			if (!scan && force_scan)
+				scan = SWAP_CLUSTER_MAX;
 			scan = div64_u64(scan * fraction[file], denominator);
 		}
-
-		/*
-		 * If zone is small or memcg is small, nr[l] can be 0.
-		 * This results no-scan on this priority and priority drop down.
-		 * For global direct reclaim, it can visit next zone and tend
-		 * not to have problems. For global kswapd, it's for zone
-		 * balancing and it need to scan a small amounts. When using
-		 * memcg, priority drop can cause big latency. So, it's better
-		 * to scan small amount. See may_noscan above.
-		 */
-		if (!scan && force_scan)
-			scan = nr_force_scan[file];
 		nr[l] = scan;
 	}
 }
@@ -1983,12 +2039,14 @@ static void shrink_zone(int priority, struct zone *zone,
 	enum lru_list l;
 	unsigned long nr_reclaimed, nr_scanned;
 	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
+	struct blk_plug plug;
 
 restart:
 	nr_reclaimed = 0;
 	nr_scanned = sc->nr_scanned;
 	get_scan_count(zone, sc, nr, priority);
 
+	blk_start_plug(&plug);
 	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
 					nr[LRU_INACTIVE_FILE]) {
 		for_each_evictable_lru(l) {
@@ -2012,6 +2070,7 @@ restart:
 		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
 			break;
 	}
+	blk_finish_plug(&plug);
 	sc->nr_reclaimed += nr_reclaimed;
 
 	/*
@@ -2044,14 +2103,19 @@ restart:
  *
  * If a zone is deemed to be full of pinned pages then just give it a light
  * scan then give up on it.
+ *
+ * This function returns true if a zone is being reclaimed for a costly
+ * high-order allocation and compaction is either ready to begin or deferred.
+ * This indicates to the caller that it should retry the allocation or fail.
  */
-static void shrink_zones(int priority, struct zonelist *zonelist,
+static bool shrink_zones(int priority, struct zonelist *zonelist,
 					struct scan_control *sc)
 {
 	struct zoneref *z;
 	struct zone *zone;
 	unsigned long nr_soft_reclaimed;
 	unsigned long nr_soft_scanned;
+	bool should_abort_reclaim = false;
 
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 					gfp_zone(sc->gfp_mask), sc->nodemask) {
@@ -2066,6 +2130,23 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
 				continue;
 			if (zone->all_unreclaimable && priority != DEF_PRIORITY)
 				continue;	/* Let kswapd poll it */
+			if (COMPACTION_BUILD) {
+				/*
+				 * If we already have plenty of memory free for
+				 * compaction in this zone, don't free any more.
+				 * Even though compaction is invoked for any
+				 * non-zero order, only frequent costly order
+				 * reclamation is disruptive enough to become a
+				 * noticable problem, like transparent huge page
+				 * allocations.
+				 */
+				if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
+					(compaction_suitable(zone, sc->order) ||
+					 compaction_deferred(zone))) {
+					should_abort_reclaim = true;
+					continue;
+				}
+			}
 			/*
 			 * This steals pages from memory cgroups over softlimit
 			 * and returns the number of reclaimed pages and
@@ -2083,6 +2164,8 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
 
 		shrink_zone(priority, zone, sc);
 	}
+
+	return should_abort_reclaim;
 }
 
 static bool zone_reclaimable(struct zone *zone)
@@ -2147,7 +2230,9 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 		sc->nr_scanned = 0;
 		if (!priority)
 			disable_swap_token(sc->mem_cgroup);
-		shrink_zones(priority, zonelist, sc);
+		if (shrink_zones(priority, zonelist, sc))
+			break;
+
 		/*
 		 * Don't shrink slabs when reclaiming memory from
 		 * over limit cgroups
@@ -2690,6 +2775,8 @@ out:
 
 			/* If balanced, clear the congested flag */
 			zone_clear_flag(zone, ZONE_CONGESTED);
+			if (i <= *classzone_idx)
+				balanced += zone->present_pages;
 		}
 	}
 
@@ -2763,7 +2850,9 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
 static int kswapd(void *p)
 {
 	unsigned long order, new_order;
+	unsigned balanced_order;
 	int classzone_idx, new_classzone_idx;
+	int balanced_classzone_idx;
 	pg_data_t *pgdat = (pg_data_t*)p;
 	struct task_struct *tsk = current;
 
@@ -2794,7 +2883,9 @@ static int kswapd(void *p)
 	set_freezable();
 
 	order = new_order = 0;
+	balanced_order = 0;
 	classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
+	balanced_classzone_idx = classzone_idx;
 	for ( ; ; ) {
 		int ret;
 
@@ -2803,7 +2894,8 @@ static int kswapd(void *p)
 		 * new request of a similar or harder type will succeed soon
 		 * so consider going to sleep on the basis we reclaimed at
 		 */
-		if (classzone_idx >= new_classzone_idx && order == new_order) {
+		if (balanced_classzone_idx >= new_classzone_idx &&
+					balanced_order == new_order) {
 			new_order = pgdat->kswapd_max_order;
 			new_classzone_idx = pgdat->classzone_idx;
 			pgdat->kswapd_max_order =  0;
@@ -2818,9 +2910,12 @@ static int kswapd(void *p)
 			order = new_order;
 			classzone_idx = new_classzone_idx;
 		} else {
-			kswapd_try_to_sleep(pgdat, order, classzone_idx);
+			kswapd_try_to_sleep(pgdat, balanced_order,
+						balanced_classzone_idx);
 			order = pgdat->kswapd_max_order;
 			classzone_idx = pgdat->classzone_idx;
+			new_order = order;
+			new_classzone_idx = classzone_idx;
 			pgdat->kswapd_max_order = 0;
 			pgdat->classzone_idx = pgdat->nr_zones - 1;
 		}
@@ -2835,7 +2930,9 @@ static int kswapd(void *p)
 		 */
 		if (!ret) {
 			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
-			order = balance_pgdat(pgdat, order, &classzone_idx);
+			balanced_classzone_idx = classzone_idx;
+			balanced_order = balance_pgdat(pgdat, order,
+						&balanced_classzone_idx);
 		}
 	}
 	return 0;
@@ -3347,66 +3444,12 @@ 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");
 }
 
 /*
@@ -3419,11 +3462,8 @@ 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;
 }
@@ -3438,6 +3478,7 @@ 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... */
 }
 
@@ -3445,19 +3486,7 @@ 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)
-		return 1;	/* 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;
 }