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

commit a8a4b7aeaf841311cb13ff0f6c4710c7a00e68d4 upstream.

This reverts commit 26e7deadaae175.

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: 26e7deadaae175 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 3fb23a21f6dd6cb6b2a663b607a511e172a8da19..7fb01d2253371f31ee37da2b65352bfc5150a72f 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1596,12 +1596,6 @@ 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]);
@@ -1609,6 +1603,12 @@ 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));