[patch -mm] mm, vmstat: suppress pcp stats for unpopulated zones in zoneinfo

[David Rientjes <rientjes@google.com>]

After "mm, vmstat: print non-populated zones in zoneinfo", /proc/zoneinfo 
will show unpopulated zones.

The per-cpu pageset statistics are not relevant for unpopulated zones and 
can be potentially lengthy, so supress them when they are not interesting.

Also moves lowmem reserve protection information above pcp stats since it 
is relevant for all zones per vm.lowmem_reserve_ratio.

Signed-off-by: David Rientjes <rientjes@google.com>
---
 mm/vmstat.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1392,18 +1392,24 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 		   zone->present_pages,
 		   zone->managed_pages);
 
-	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
-		seq_printf(m, "\n      %-12s %lu", vmstat_text[i],
-				zone_page_state(zone, i));
-
 	seq_printf(m,
 		   "\n        protection: (%ld",
 		   zone->lowmem_reserve[0]);
 	for (i = 1; i < ARRAY_SIZE(zone->lowmem_reserve); i++)
 		seq_printf(m, ", %ld", zone->lowmem_reserve[i]);
-	seq_printf(m,
-		   ")"
-		   "\n  pagesets");
+	seq_putc(m, ')');
+
+	/* If unpopulated, no other information is useful */
+	if (!populated_zone(zone)) {
+		seq_putc(m, '\n');
+		return;
+	}
+
+	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
+		seq_printf(m, "\n      %-12s %lu", vmstat_text[i],
+				zone_page_state(zone, i));
+
+	seq_printf(m, "\n  pagesets");
 	for_each_online_cpu(i) {
 		struct per_cpu_pageset *pageset;