Revert "mm/vmstat.c: do not show lowmem reserve protection information of empty zone"

This reverts commit 9b9baaf8384add.

Sonny reported that one of their tests started failing on the latest
kernel on their Chrome OS platform.  The root cause is that the above
commit removed the protection line of empty zone, while the parser used in
the test relies on the protection line to mark the end of each zone.

Let's revert it to avoid breaking userspace testing or applications.

Fixes: 9b9baaf8384add ("mm/vmstat.c: do not show lowmem reserve protection information of empty zone)"
Reported-by: Sonny Rao <sonnyrao@chromium.org>
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>	[5.8.x]
Link: http://lkml.kernel.org/r/20200811075412.12872-1-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 727a26d1ec1d2d3c22f58656d2ae921582a2bcf3..e670f910cd2f3ba86ae0d75ba4a0f85b7ab907f3 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1642,12 +1642,6 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
                   zone->present_pages,
                   zone_managed_pages(zone));
 
-       /* If unpopulated, no other information is useful */
-       if (!populated_zone(zone)) {
-               seq_putc(m, '\n');
-               return;
-       }
-
        seq_printf(m,
                   "\n        protection: (%ld",
                   zone->lowmem_reserve[0]);
@@ -1655,6 +1649,12 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
                seq_printf(m, ", %ld", zone->lowmem_reserve[i]);
        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", zone_stat_name(i),
                           zone_page_state(zone, i));