[PATCH v2 2/9] mm/vmstat: show start_pfn when zone spans pages

[Doug Berger <opendmb@gmail.com>]

A zone that overlaps with another zone may span a range of pages
that are not present. In this case, displaying the start_pfn of
the zone allows the zone page range to be identified.

Signed-off-by: Doug Berger <opendmb@gmail.com>
---
 mm/vmstat.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 90af9a8572f5..e2f19f2b7615 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1717,6 +1717,11 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 
 	/* If unpopulated, no other information is useful */
 	if (!populated_zone(zone)) {
+		/* Show start_pfn for empty overlapped zones */
+		if (zone->spanned_pages)
+			seq_printf(m,
+				   "\n  start_pfn:           %lu",
+				   zone->zone_start_pfn);
 		seq_putc(m, '\n');
 		return;
 	}
-- 
2.25.1