mm: remove vm_total_pages

The global variable "vm_total_pages" is a relic from older days.  There is
only a single user that reads the variable - build_all_zonelists() - and
the first thing it does is update it.

Use a local variable in build_all_zonelists() instead and remove the
global variable.

Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Minchan Kim <minchan@kernel.org>
Link: http://lkml.kernel.org/r/20200619132410.23859-2-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -170,11 +170,6 @@ struct scan_control {
  * From 0 .. 200.  Higher means more swappy.
  */
 int vm_swappiness = 60;
-/*
- * The total number of pages which are beyond the high watermark within all
- * zones.
- */
-unsigned long vm_total_pages;
 
 static void set_task_reclaim_state(struct task_struct *task,
 				   struct reclaim_state *rs)