vmstat: call fold_vm_zone_numa_events() before show per zone NUMA event

Since 5.14-rc1, NUMA events will only be folded from per-CPU statistics to
per zone and global statistics when the user actually needs it.

Currently, the kernel has performs the fold operation when reading
/proc/vmstat, but does not perform the fold operation in /proc/zoneinfo. 
This can lead to inaccuracies in the following statistics in zoneinfo:
- numa_hit
- numa_miss
- numa_foreign
- numa_interleave
- numa_local
- numa_other

Therefore, before printing per-zone vm_numa_event when reading
/proc/zoneinfo, we should also perform the fold operation.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: f19298b ("mm/vmstat: convert NUMA statistics to basic NUMA counters")
Signed-off-by: MengEn Sun <[email protected]>
Reviewed-by: JinLiang Zheng <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: MengEn Sun

mm/vmstat.c

@@ -1780,6 +1780,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 			   zone_page_state(zone, i));
 
 #ifdef CONFIG_NUMA
+	fold_vm_zone_numa_events(zone);
 	for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++)
 		seq_printf(m, "\n      %-12s %lu", numa_stat_name(i),
 			   zone_numa_event_state(zone, i));