mm: rename global_page_state to global_zone_page_state

global_page_state is error prone as a recent bug report pointed out [1].
It only returns proper values for zone based counters as the enum it
gets suggests.  We already have global_node_page_state so let's rename
global_page_state to global_zone_page_state to be more explicit here.
All existing users seems to be correct:

$ git grep "global_page_state(NR_" | sed 's@.*(\(NR_[A-Z_]*\)).*@\1@' | sort | uniq -c
      2 NR_BOUNCE
      2 NR_FREE_CMA_PAGES
     11 NR_FREE_PAGES
      1 NR_KERNEL_STACK_KB
      1 NR_MLOCK
      2 NR_PAGETABLE

This patch shouldn't introduce any functional change.

[1] http://lkml.kernel.org/r/201707260628.v6Q6SmaS030814@www262.sakura.ne.jp

Link: http://lkml.kernel.org/r/20170801134256.5400-2-hannes@cmpxchg.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mmap.c b/mm/mmap.c
index f19efcf..9800e29 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3514,7 +3514,7 @@ static int init_user_reserve(void)
 {
 	unsigned long free_kbytes;
 
-	free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
 
 	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
 	return 0;
@@ -3535,7 +3535,7 @@ static int init_admin_reserve(void)
 {
 	unsigned long free_kbytes;
 
-	free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
 
 	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
 	return 0;
@@ -3579,7 +3579,7 @@ static int reserve_mem_notifier(struct notifier_block *nb,
 
 		break;
 	case MEM_OFFLINE:
-		free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
+		free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
 
 		if (sysctl_user_reserve_kbytes > free_kbytes) {
 			init_user_reserve();