1 files changed, 137 insertions, 141 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b2f5deb3603c..3792dd19788c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -79,6 +79,12 @@ struct scan_control {
 	 */
 	struct mem_cgroup *target_mem_cgroup;
 
+	/*
+	 * Scan pressure balancing between anon and file LRUs
+	 */
+	unsigned long	anon_cost;
+	unsigned long	file_cost;
+
 	/* Can active pages be deactivated as part of reclaim? */
 #define DEACTIVATE_ANON 1
 #define DEACTIVATE_FILE 2
@@ -161,7 +167,7 @@ struct scan_control {
 #endif
 
 /*
- * From 0 .. 100.  Higher means more swappy.
+ * From 0 .. 200.  Higher means more swappy.
  */
 int vm_swappiness = 60;
 /*
@@ -1066,17 +1072,17 @@ static void page_check_dirty_writeback(struct page *page,
 /*
  * shrink_page_list() returns the number of reclaimed pages
  */
-static unsigned long shrink_page_list(struct list_head *page_list,
-				      struct pglist_data *pgdat,
-				      struct scan_control *sc,
-				      enum ttu_flags ttu_flags,
-				      struct reclaim_stat *stat,
-				      bool ignore_references)
+static unsigned int shrink_page_list(struct list_head *page_list,
+				     struct pglist_data *pgdat,
+				     struct scan_control *sc,
+				     enum ttu_flags ttu_flags,
+				     struct reclaim_stat *stat,
+				     bool ignore_references)
 {
 	LIST_HEAD(ret_pages);
 	LIST_HEAD(free_pages);
-	unsigned nr_reclaimed = 0;
-	unsigned pgactivate = 0;
+	unsigned int nr_reclaimed = 0;
+	unsigned int pgactivate = 0;
 
 	memset(stat, 0, sizeof(*stat));
 	cond_resched();
@@ -1295,11 +1301,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 */
 		if (page_mapped(page)) {
 			enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH;
+			bool was_swapbacked = PageSwapBacked(page);
 
 			if (unlikely(PageTransHuge(page)))
 				flags |= TTU_SPLIT_HUGE_PMD;
+
 			if (!try_to_unmap(page, flags)) {
 				stat->nr_unmap_fail += nr_pages;
+				if (!was_swapbacked && PageSwapBacked(page))
+					stat->nr_lazyfree_fail += nr_pages;
 				goto activate_locked;
 			}
 		}
@@ -1349,6 +1359,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			case PAGE_ACTIVATE:
 				goto activate_locked;
 			case PAGE_SUCCESS:
+				stat->nr_pageout += hpage_nr_pages(page);
+
 				if (PageWriteback(page))
 					goto keep;
 				if (PageDirty(page))
@@ -1438,7 +1450,7 @@ free_it:
 		 * appear not as the counts should be low
 		 */
 		if (unlikely(PageTransHuge(page)))
-			(*get_compound_page_dtor(page))(page);
+			destroy_compound_page(page);
 		else
 			list_add(&page->lru, &free_pages);
 		continue;
@@ -1483,7 +1495,7 @@ keep:
 	return nr_reclaimed;
 }
 
-unsigned long reclaim_clean_pages_from_list(struct zone *zone,
+unsigned int reclaim_clean_pages_from_list(struct zone *zone,
 					    struct list_head *page_list)
 {
 	struct scan_control sc = {
@@ -1491,8 +1503,8 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
 		.priority = DEF_PRIORITY,
 		.may_unmap = 1,
 	};
-	struct reclaim_stat dummy_stat;
-	unsigned long ret;
+	struct reclaim_stat stat;
+	unsigned int nr_reclaimed;
 	struct page *page, *next;
 	LIST_HEAD(clean_pages);
 
@@ -1504,11 +1516,21 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
 		}
 	}
 
-	ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
-			TTU_IGNORE_ACCESS, &dummy_stat, true);
+	nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
+			TTU_IGNORE_ACCESS, &stat, true);
 	list_splice(&clean_pages, page_list);
-	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret);
-	return ret;
+	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -nr_reclaimed);
+	/*
+	 * Since lazyfree pages are isolated from file LRU from the beginning,
+	 * they will rotate back to anonymous LRU in the end if it failed to
+	 * discard so isolated count will be mismatched.
+	 * Compensate the isolated count for both LRU lists.
+	 */
+	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
+			    stat.nr_lazyfree_fail);
+	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
+			    -stat.nr_lazyfree_fail);
+	return nr_reclaimed;
 }
 
 /*
@@ -1602,10 +1624,7 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,
 		if (!nr_zone_taken[zid])
 			continue;
 
-		__update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
-#ifdef CONFIG_MEMCG
-		mem_cgroup_update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
-#endif
+		update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
 	}
 
 }
@@ -1859,7 +1878,7 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
 
 			if (unlikely(PageCompound(page))) {
 				spin_unlock_irq(&pgdat->lru_lock);
-				(*get_compound_page_dtor(page))(page);
+				destroy_compound_page(page);
 				spin_lock_irq(&pgdat->lru_lock);
 			} else
 				list_add(&page->lru, &pages_to_free);
@@ -1899,13 +1918,12 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 {
 	LIST_HEAD(page_list);
 	unsigned long nr_scanned;
-	unsigned long nr_reclaimed = 0;
+	unsigned int nr_reclaimed = 0;
 	unsigned long nr_taken;
 	struct reclaim_stat stat;
-	int file = is_file_lru(lru);
+	bool file = is_file_lru(lru);
 	enum vm_event_item item;
 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
-	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
 	bool stalled = false;
 
 	while (unlikely(too_many_isolated(pgdat, file, sc))) {
@@ -1929,12 +1947,12 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 				     &nr_scanned, sc, lru);
 
 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
-	reclaim_stat->recent_scanned[file] += nr_taken;
-
 	item = current_is_kswapd() ? PGSCAN_KSWAPD : PGSCAN_DIRECT;
 	if (!cgroup_reclaim(sc))
 		__count_vm_events(item, nr_scanned);
 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
+	__count_vm_events(PGSCAN_ANON + file, nr_scanned);
+
 	spin_unlock_irq(&pgdat->lru_lock);
 
 	if (nr_taken == 0)
@@ -1945,16 +1963,15 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 	spin_lock_irq(&pgdat->lru_lock);
 
+	move_pages_to_lru(lruvec, &page_list);
+
+	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+	lru_note_cost(lruvec, file, stat.nr_pageout);
 	item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
 	if (!cgroup_reclaim(sc))
 		__count_vm_events(item, nr_reclaimed);
 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
-	reclaim_stat->recent_rotated[0] += stat.nr_activate[0];
-	reclaim_stat->recent_rotated[1] += stat.nr_activate[1];
-
-	move_pages_to_lru(lruvec, &page_list);
-
-	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
 
 	spin_unlock_irq(&pgdat->lru_lock);
 
@@ -2001,7 +2018,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	LIST_HEAD(l_active);
 	LIST_HEAD(l_inactive);
 	struct page *page;
-	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
 	unsigned nr_deactivate, nr_activate;
 	unsigned nr_rotated = 0;
 	int file = is_file_lru(lru);
@@ -2015,7 +2031,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
 				     &nr_scanned, sc, lru);
 
 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
-	reclaim_stat->recent_scanned[file] += nr_taken;
 
 	__count_vm_events(PGREFILL, nr_scanned);
 	__count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
@@ -2042,7 +2057,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
 
 		if (page_referenced(page, 0, sc->target_mem_cgroup,
 				    &vm_flags)) {
-			nr_rotated += hpage_nr_pages(page);
 			/*
 			 * Identify referenced, file-backed active pages and
 			 * give them one more trip around the active list. So
@@ -2053,6 +2067,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
 			 * so we ignore them here.
 			 */
 			if ((vm_flags & VM_EXEC) && page_is_file_lru(page)) {
+				nr_rotated += hpage_nr_pages(page);
 				list_add(&page->lru, &l_active);
 				continue;
 			}
@@ -2067,13 +2082,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	 * Move pages back to the lru list.
 	 */
 	spin_lock_irq(&pgdat->lru_lock);
-	/*
-	 * Count referenced pages from currently used mappings as rotated,
-	 * even though only some of them are actually re-activated.  This
-	 * helps balance scan pressure between file and anonymous pages in
-	 * get_scan_count.
-	 */
-	reclaim_stat->recent_rotated[file] += nr_rotated;
 
 	nr_activate = move_pages_to_lru(lruvec, &l_active);
 	nr_deactivate = move_pages_to_lru(lruvec, &l_inactive);
@@ -2095,7 +2103,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
 unsigned long reclaim_pages(struct list_head *page_list)
 {
 	int nid = NUMA_NO_NODE;
-	unsigned long nr_reclaimed = 0;
+	unsigned int nr_reclaimed = 0;
 	LIST_HEAD(node_page_list);
 	struct reclaim_stat dummy_stat;
 	struct page *page;
@@ -2229,14 +2237,11 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 			   unsigned long *nr)
 {
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+	unsigned long anon_cost, file_cost, total_cost;
 	int swappiness = mem_cgroup_swappiness(memcg);
-	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
 	u64 fraction[2];
 	u64 denominator = 0;	/* gcc */
-	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
-	unsigned long anon_prio, file_prio;
 	enum scan_balance scan_balance;
-	unsigned long anon, file;
 	unsigned long ap, fp;
 	enum lru_list lru;
 
@@ -2286,57 +2291,35 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 	}
 
 	scan_balance = SCAN_FRACT;
-
-	/*
-	 * With swappiness at 100, anonymous and file have the same priority.
-	 * This scanning priority is essentially the inverse of IO cost.
-	 */
-	anon_prio = swappiness;
-	file_prio = 200 - anon_prio;
-
 	/*
-	 * OK, so we have swap space and a fair amount of page cache
-	 * pages.  We use the recently rotated / recently scanned
-	 * ratios to determine how valuable each cache is.
+	 * Calculate the pressure balance between anon and file pages.
+	 *
+	 * The amount of pressure we put on each LRU is inversely
+	 * proportional to the cost of reclaiming each list, as
+	 * determined by the share of pages that are refaulting, times
+	 * the relative IO cost of bringing back a swapped out
+	 * anonymous page vs reloading a filesystem page (swappiness).
 	 *
-	 * Because workloads change over time (and to avoid overflow)
-	 * we keep these statistics as a floating average, which ends
-	 * up weighing recent references more than old ones.
+	 * Although we limit that influence to ensure no list gets
+	 * left behind completely: at least a third of the pressure is
+	 * applied, before swappiness.
 	 *
-	 * anon in [0], file in [1]
+	 * With swappiness at 100, anon and file have equal IO cost.
 	 */
+	total_cost = sc->anon_cost + sc->file_cost;
+	anon_cost = total_cost + sc->anon_cost;
+	file_cost = total_cost + sc->file_cost;
+	total_cost = anon_cost + file_cost;
 
-	anon  = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON, MAX_NR_ZONES) +
-		lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, MAX_NR_ZONES);
-	file  = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES) +
-		lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES);
+	ap = swappiness * (total_cost + 1);
+	ap /= anon_cost + 1;
 
-	spin_lock_irq(&pgdat->lru_lock);
-	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
-		reclaim_stat->recent_scanned[0] /= 2;
-		reclaim_stat->recent_rotated[0] /= 2;
-	}
-
-	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
-		reclaim_stat->recent_scanned[1] /= 2;
-		reclaim_stat->recent_rotated[1] /= 2;
-	}
-
-	/*
-	 * The amount of pressure on anon vs file pages is inversely
-	 * proportional to the fraction of recently scanned pages on
-	 * each list that were recently referenced and in active use.
-	 */
-	ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
-	ap /= reclaim_stat->recent_rotated[0] + 1;
-
-	fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
-	fp /= reclaim_stat->recent_rotated[1] + 1;
-	spin_unlock_irq(&pgdat->lru_lock);
+	fp = (200 - swappiness) * (total_cost + 1);
+	fp /= file_cost + 1;
 
 	fraction[0] = ap;
 	fraction[1] = fp;
-	denominator = ap + fp + 1;
+	denominator = ap + fp;
 out:
 	for_each_evictable_lru(lru) {
 		int file = is_file_lru(lru);
@@ -2566,7 +2549,7 @@ static bool in_reclaim_compaction(struct scan_control *sc)
  * Reclaim/compaction is used for high-order allocation requests. It reclaims
  * order-0 pages before compacting the zone. should_continue_reclaim() returns
  * true if more pages should be reclaimed such that when the page allocator
- * calls try_to_compact_zone() that it will have enough free pages to succeed.
+ * calls try_to_compact_pages() that it will have enough free pages to succeed.
  * It will give up earlier than that if there is difficulty reclaiming pages.
  */
 static inline bool should_continue_reclaim(struct pglist_data *pgdat,
@@ -2697,6 +2680,14 @@ again:
 	nr_scanned = sc->nr_scanned;
 
 	/*
+	 * Determine the scan balance between anon and file LRUs.
+	 */
+	spin_lock_irq(&pgdat->lru_lock);
+	sc->anon_cost = target_lruvec->anon_cost;
+	sc->file_cost = target_lruvec->file_cost;
+	spin_unlock_irq(&pgdat->lru_lock);
+
+	/*
 	 * Target desirable inactive:active list ratios for the anon
 	 * and file LRU lists.
 	 */
@@ -3131,8 +3122,8 @@ static bool allow_direct_reclaim(pg_data_t *pgdat)
 
 	/* kswapd must be awake if processes are being throttled */
 	if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) {
-		if (READ_ONCE(pgdat->kswapd_classzone_idx) > ZONE_NORMAL)
-			WRITE_ONCE(pgdat->kswapd_classzone_idx, ZONE_NORMAL);
+		if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL)
+			WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL);
 
 		wake_up_interruptible(&pgdat->kswapd_wait);
 	}
@@ -3385,7 +3376,7 @@ static void age_active_anon(struct pglist_data *pgdat,
 	} while (memcg);
 }
 
-static bool pgdat_watermark_boosted(pg_data_t *pgdat, int classzone_idx)
+static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx)
 {
 	int i;
 	struct zone *zone;
@@ -3397,7 +3388,7 @@ static bool pgdat_watermark_boosted(pg_data_t *pgdat, int classzone_idx)
 	 * start prematurely when there is no boosting and a lower
 	 * zone is balanced.
 	 */
-	for (i = classzone_idx; i >= 0; i--) {
+	for (i = highest_zoneidx; i >= 0; i--) {
 		zone = pgdat->node_zones + i;
 		if (!managed_zone(zone))
 			continue;
@@ -3411,9 +3402,9 @@ static bool pgdat_watermark_boosted(pg_data_t *pgdat, int classzone_idx)
 
 /*
  * Returns true if there is an eligible zone balanced for the request order
- * and classzone_idx
+ * and highest_zoneidx
  */
-static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
+static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx)
 {
 	int i;
 	unsigned long mark = -1;
@@ -3423,19 +3414,19 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
 	 * Check watermarks bottom-up as lower zones are more likely to
 	 * meet watermarks.
 	 */
-	for (i = 0; i <= classzone_idx; i++) {
+	for (i = 0; i <= highest_zoneidx; i++) {
 		zone = pgdat->node_zones + i;
 
 		if (!managed_zone(zone))
 			continue;
 
 		mark = high_wmark_pages(zone);
-		if (zone_watermark_ok_safe(zone, order, mark, classzone_idx))
+		if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx))
 			return true;
 	}
 
 	/*
-	 * If a node has no populated zone within classzone_idx, it does not
+	 * If a node has no populated zone within highest_zoneidx, it does not
 	 * need balancing by definition. This can happen if a zone-restricted
 	 * allocation tries to wake a remote kswapd.
 	 */
@@ -3461,7 +3452,8 @@ static void clear_pgdat_congested(pg_data_t *pgdat)
  *
  * Returns true if kswapd is ready to sleep
  */
-static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx)
+static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order,
+				int highest_zoneidx)
 {
 	/*
 	 * The throttled processes are normally woken up in balance_pgdat() as
@@ -3483,7 +3475,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx)
 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES)
 		return true;
 
-	if (pgdat_balanced(pgdat, order, classzone_idx)) {
+	if (pgdat_balanced(pgdat, order, highest_zoneidx)) {
 		clear_pgdat_congested(pgdat);
 		return true;
 	}
@@ -3547,7 +3539,7 @@ static bool kswapd_shrink_node(pg_data_t *pgdat,
  * or lower is eligible for reclaim until at least one usable zone is
  * balanced.
  */
-static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
+static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
 {
 	int i;
 	unsigned long nr_soft_reclaimed;
@@ -3575,7 +3567,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 	 * stall or direct reclaim until kswapd is finished.
 	 */
 	nr_boost_reclaim = 0;
-	for (i = 0; i <= classzone_idx; i++) {
+	for (i = 0; i <= highest_zoneidx; i++) {
 		zone = pgdat->node_zones + i;
 		if (!managed_zone(zone))
 			continue;
@@ -3593,7 +3585,7 @@ restart:
 		bool balanced;
 		bool ret;
 
-		sc.reclaim_idx = classzone_idx;
+		sc.reclaim_idx = highest_zoneidx;
 
 		/*
 		 * If the number of buffer_heads exceeds the maximum allowed
@@ -3623,7 +3615,7 @@ restart:
 		 * on the grounds that the normal reclaim should be enough to
 		 * re-evaluate if boosting is required when kswapd next wakes.
 		 */
-		balanced = pgdat_balanced(pgdat, sc.order, classzone_idx);
+		balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx);
 		if (!balanced && nr_boost_reclaim) {
 			nr_boost_reclaim = 0;
 			goto restart;
@@ -3723,7 +3715,7 @@ out:
 	if (boosted) {
 		unsigned long flags;
 
-		for (i = 0; i <= classzone_idx; i++) {
+		for (i = 0; i <= highest_zoneidx; i++) {
 			if (!zone_boosts[i])
 				continue;
 
@@ -3738,7 +3730,7 @@ out:
 		 * As there is now likely space, wakeup kcompact to defragment
 		 * pageblocks.
 		 */
-		wakeup_kcompactd(pgdat, pageblock_order, classzone_idx);
+		wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx);
 	}
 
 	snapshot_refaults(NULL, pgdat);
@@ -3756,22 +3748,22 @@ out:
 }
 
 /*
- * The pgdat->kswapd_classzone_idx is used to pass the highest zone index to be
- * reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is not
- * a valid index then either kswapd runs for first time or kswapd couldn't sleep
- * after previous reclaim attempt (node is still unbalanced). In that case
- * return the zone index of the previous kswapd reclaim cycle.
+ * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to
+ * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
+ * not a valid index then either kswapd runs for first time or kswapd couldn't
+ * sleep after previous reclaim attempt (node is still unbalanced). In that
+ * case return the zone index of the previous kswapd reclaim cycle.
  */
-static enum zone_type kswapd_classzone_idx(pg_data_t *pgdat,
-					   enum zone_type prev_classzone_idx)
+static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat,
+					   enum zone_type prev_highest_zoneidx)
 {
-	enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_classzone_idx);
+	enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
 
-	return curr_idx == MAX_NR_ZONES ? prev_classzone_idx : curr_idx;
+	return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx;
 }
 
 static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order,
-				unsigned int classzone_idx)
+				unsigned int highest_zoneidx)
 {
 	long remaining = 0;
 	DEFINE_WAIT(wait);
@@ -3788,7 +3780,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_o
 	 * eligible zone balanced that it's also unlikely that compaction will
 	 * succeed.
 	 */
-	if (prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) {
+	if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
 		/*
 		 * Compaction records what page blocks it recently failed to
 		 * isolate pages from and skips them in the future scanning.
@@ -3801,18 +3793,19 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_o
 		 * We have freed the memory, now we should compact it to make
 		 * allocation of the requested order possible.
 		 */
-		wakeup_kcompactd(pgdat, alloc_order, classzone_idx);
+		wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx);
 
 		remaining = schedule_timeout(HZ/10);
 
 		/*
-		 * If woken prematurely then reset kswapd_classzone_idx and
+		 * If woken prematurely then reset kswapd_highest_zoneidx and
 		 * order. The values will either be from a wakeup request or
 		 * the previous request that slept prematurely.
 		 */
 		if (remaining) {
-			WRITE_ONCE(pgdat->kswapd_classzone_idx,
-				   kswapd_classzone_idx(pgdat, classzone_idx));
+			WRITE_ONCE(pgdat->kswapd_highest_zoneidx,
+					kswapd_highest_zoneidx(pgdat,
+							highest_zoneidx));
 
 			if (READ_ONCE(pgdat->kswapd_order) < reclaim_order)
 				WRITE_ONCE(pgdat->kswapd_order, reclaim_order);
@@ -3827,7 +3820,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_o
 	 * go fully to sleep until explicitly woken up.
 	 */
 	if (!remaining &&
-	    prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) {
+	    prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) {
 		trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
 
 		/*
@@ -3869,7 +3862,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_o
 static int kswapd(void *p)
 {
 	unsigned int alloc_order, reclaim_order;
-	unsigned int classzone_idx = MAX_NR_ZONES - 1;
+	unsigned int highest_zoneidx = MAX_NR_ZONES - 1;
 	pg_data_t *pgdat = (pg_data_t*)p;
 	struct task_struct *tsk = current;
 	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
@@ -3893,22 +3886,24 @@ static int kswapd(void *p)
 	set_freezable();
 
 	WRITE_ONCE(pgdat->kswapd_order, 0);
-	WRITE_ONCE(pgdat->kswapd_classzone_idx, MAX_NR_ZONES);
+	WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
 	for ( ; ; ) {
 		bool ret;
 
 		alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
-		classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
+		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
+							highest_zoneidx);
 
 kswapd_try_sleep:
 		kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order,
-					classzone_idx);
+					highest_zoneidx);
 
-		/* Read the new order and classzone_idx */
+		/* Read the new order and highest_zoneidx */
 		alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
-		classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx);
+		highest_zoneidx = kswapd_highest_zoneidx(pgdat,
+							highest_zoneidx);
 		WRITE_ONCE(pgdat->kswapd_order, 0);
-		WRITE_ONCE(pgdat->kswapd_classzone_idx, MAX_NR_ZONES);
+		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES);
 
 		ret = try_to_freeze();
 		if (kthread_should_stop())
@@ -3929,9 +3924,10 @@ kswapd_try_sleep:
 		 * but kcompactd is woken to compact for the original
 		 * request (alloc_order).
 		 */
-		trace_mm_vmscan_kswapd_wake(pgdat->node_id, classzone_idx,
+		trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx,
 						alloc_order);
-		reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx);
+		reclaim_order = balance_pgdat(pgdat, alloc_order,
+						highest_zoneidx);
 		if (reclaim_order < alloc_order)
 			goto kswapd_try_sleep;
 	}
@@ -3949,7 +3945,7 @@ kswapd_try_sleep:
  * needed.
  */
 void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
-		   enum zone_type classzone_idx)
+		   enum zone_type highest_zoneidx)
 {
 	pg_data_t *pgdat;
 	enum zone_type curr_idx;
@@ -3961,10 +3957,10 @@ void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
 		return;
 
 	pgdat = zone->zone_pgdat;
-	curr_idx = READ_ONCE(pgdat->kswapd_classzone_idx);
+	curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx);
 
-	if (curr_idx == MAX_NR_ZONES || curr_idx < classzone_idx)
-		WRITE_ONCE(pgdat->kswapd_classzone_idx, classzone_idx);
+	if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx)
+		WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx);
 
 	if (READ_ONCE(pgdat->kswapd_order) < order)
 		WRITE_ONCE(pgdat->kswapd_order, order);
@@ -3974,8 +3970,8 @@ void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
 
 	/* Hopeless node, leave it to direct reclaim if possible */
 	if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ||
-	    (pgdat_balanced(pgdat, order, classzone_idx) &&
-	     !pgdat_watermark_boosted(pgdat, classzone_idx))) {
+	    (pgdat_balanced(pgdat, order, highest_zoneidx) &&
+	     !pgdat_watermark_boosted(pgdat, highest_zoneidx))) {
 		/*
 		 * There may be plenty of free memory available, but it's too
 		 * fragmented for high-order allocations.  Wake up kcompactd
@@ -3984,11 +3980,11 @@ void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
 		 * ratelimit its work.
 		 */
 		if (!(gfp_flags & __GFP_DIRECT_RECLAIM))
-			wakeup_kcompactd(pgdat, order, classzone_idx);
+			wakeup_kcompactd(pgdat, order, highest_zoneidx);
 		return;
 	}
 
-	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, classzone_idx, order,
+	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order,
 				      gfp_flags);
 	wake_up_interruptible(&pgdat->kswapd_wait);
 }