vmscan: update isolated page counters outside of main path in shrink_inactive_list()

When shrink_inactive_list() isolates pages, it updates a number of
counters using temporary variables to gather them.  These consume stack
and it's in the main path that calls ->writepage().  This patch moves the
accounting updates outside of the main path to reduce stack usage.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -1076,7 +1076,8 @@ static unsigned long clear_active_flags(struct list_head *page_list,
 			ClearPageActive(page);
 			nr_active++;
 		}
-		count[lru]++;
+		if (count)
+			count[lru]++;
 	}
 
 	return nr_active;
@@ -1156,12 +1157,13 @@ static int too_many_isolated(struct zone *zone, int file,
  * TODO: Try merging with migrations version of putback_lru_pages
  */
 static noinline_for_stack void
-putback_lru_pages(struct zone *zone, struct zone_reclaim_stat *reclaim_stat,
+putback_lru_pages(struct zone *zone, struct scan_control *sc,
 				unsigned long nr_anon, unsigned long nr_file,
 				struct list_head *page_list)
 {
 	struct page *page;
 	struct pagevec pvec;
+	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
 
 	pagevec_init(&pvec, 1);
 
@@ -1200,6 +1202,37 @@ putback_lru_pages(struct zone *zone, struct zone_reclaim_stat *reclaim_stat,
 	pagevec_release(&pvec);
 }
 
+static noinline_for_stack void update_isolated_counts(struct zone *zone,
+					struct scan_control *sc,
+					unsigned long *nr_anon,
+					unsigned long *nr_file,
+					struct list_head *isolated_list)
+{
+	unsigned long nr_active;
+	unsigned int count[NR_LRU_LISTS] = { 0, };
+	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
+
+	nr_active = clear_active_flags(isolated_list, count);
+	__count_vm_events(PGDEACTIVATE, nr_active);
+
+	__mod_zone_page_state(zone, NR_ACTIVE_FILE,
+			      -count[LRU_ACTIVE_FILE]);
+	__mod_zone_page_state(zone, NR_INACTIVE_FILE,
+			      -count[LRU_INACTIVE_FILE]);
+	__mod_zone_page_state(zone, NR_ACTIVE_ANON,
+			      -count[LRU_ACTIVE_ANON]);
+	__mod_zone_page_state(zone, NR_INACTIVE_ANON,
+			      -count[LRU_INACTIVE_ANON]);
+
+	*nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
+	*nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
+	__mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
+	__mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
+
+	reclaim_stat->recent_scanned[0] += *nr_anon;
+	reclaim_stat->recent_scanned[1] += *nr_file;
+}
+
 /*
  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
  * of reclaimed pages
@@ -1211,10 +1244,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 	LIST_HEAD(page_list);
 	unsigned long nr_scanned;
 	unsigned long nr_reclaimed = 0;
-	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
 	unsigned long nr_taken;
 	unsigned long nr_active;
-	unsigned int count[NR_LRU_LISTS] = { 0, };
 	unsigned long nr_anon;
 	unsigned long nr_file;
 
@@ -1261,25 +1292,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 		return 0;
 	}
 
-	nr_active = clear_active_flags(&page_list, count);
+	update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
-	__count_vm_events(PGDEACTIVATE, nr_active);
-
-	__mod_zone_page_state(zone, NR_ACTIVE_FILE,
-					-count[LRU_ACTIVE_FILE]);
-	__mod_zone_page_state(zone, NR_INACTIVE_FILE,
-					-count[LRU_INACTIVE_FILE]);
-	__mod_zone_page_state(zone, NR_ACTIVE_ANON,
-					-count[LRU_ACTIVE_ANON]);
-	__mod_zone_page_state(zone, NR_INACTIVE_ANON,
-					-count[LRU_INACTIVE_ANON]);
-
-	nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
-	nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
-	__mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
-	__mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
-
-	reclaim_stat->recent_scanned[0] += nr_anon;
-	reclaim_stat->recent_scanned[1] += nr_file;
 
 	spin_unlock_irq(&zone->lru_lock);
 
@@ -1299,7 +1312,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 		 * The attempt at page out may have made some
 		 * of the pages active, mark them inactive again.
 		 */
-		nr_active = clear_active_flags(&page_list, count);
+		nr_active = clear_active_flags(&page_list, NULL);
 		count_vm_events(PGDEACTIVATE, nr_active);
 
 		nr_reclaimed += shrink_page_list(&page_list, sc, PAGEOUT_IO_SYNC);
@@ -1310,7 +1323,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
 		__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
 	__count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
 
-	putback_lru_pages(zone, reclaim_stat, nr_anon, nr_file, &page_list);
+	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
 	return nr_reclaimed;
 }