[PATCH 4.19.y 1/2] mm: hide incomplete nr_indirectly_reclaimable in /proc/zoneinfo

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

From: Roman Gushchin <guro@fb.com>

[ commit c29f9010a35604047f96a7e9d6cbabfa36d996d1 from 4.14.y ]

Yongqin reported that /proc/zoneinfo format is broken in 4.14
due to commit 7aaf77272358 ("mm: don't show nr_indirectly_reclaimable
in /proc/vmstat")

Node 0, zone      DMA
  per-node stats
      nr_inactive_anon 403
      nr_active_anon 89123
      nr_inactive_file 128887
      nr_active_file 47377
      nr_unevictable 2053
      nr_slab_reclaimable 7510
      nr_slab_unreclaimable 10775
      nr_isolated_anon 0
      nr_isolated_file 0
      <...>
      nr_vmscan_write 0
      nr_vmscan_immediate_reclaim 0
      nr_dirtied   6022
      nr_written   5985
                   74240
      ^^^^^^^^^^
  pages free     131656

The problem is caused by the nr_indirectly_reclaimable counter,
which is hidden from the /proc/vmstat, but not from the
/proc/zoneinfo. Let's fix this inconsistency and hide the
counter from /proc/zoneinfo exactly as from /proc/vmstat.

BTW, in 4.19+ the counter has been renamed and exported by
the commit b29940c1abd7 ("mm: rename and change semantics of
nr_indirectly_reclaimable_bytes"), so there is no such a problem
anymore.

Cc: <stable@vger.kernel.org> # 4.19.y
Fixes: 7aaf77272358 ("mm: don't show nr_indirectly_reclaimable in /proc/vmstat")
Reported-by: Yongqin Liu <yongqin.liu@linaro.org>
Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 mm/vmstat.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 72ef3936d15d..7b8937cb2876 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1550,6 +1550,10 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 	if (is_zone_first_populated(pgdat, zone)) {
 		seq_printf(m, "\n  per-node stats");
 		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
+			/* Skip hidden vmstat items. */
+			if (*vmstat_text[i + NR_VM_ZONE_STAT_ITEMS +
+					 NR_VM_NUMA_STAT_ITEMS] == '\0')
+				continue;
 			seq_printf(m, "\n      %-12s %lu",
 				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS +
 				NR_VM_NUMA_STAT_ITEMS],