mm: convert totalram_pages and totalhigh_pages variables to atomic

totalram_pages and totalhigh_pages are made static inline function.

Main motivation was that managed_page_count_lock handling was complicating
things.  It was discussed in length here,
https://lore.kernel.org/patchwork/patch/995739/#1181785 So it seemes
better to remove the lock and convert variables to atomic, with preventing
poteintial store-to-read tearing as a bonus.

[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/1542090790-21750-4-git-send-email-arunks@codeaurora.org
Signed-off-by: Arun KS <arunks@codeaurora.org>
Suggested-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/shmem.c b/mm/shmem.c
index b1f0f54..6ece1e2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -109,13 +109,14 @@ struct shmem_falloc {
 #ifdef CONFIG_TMPFS
 static unsigned long shmem_default_max_blocks(void)
 {
-	return totalram_pages / 2;
+	return totalram_pages() / 2;
 }
 
 static unsigned long shmem_default_max_inodes(void)
 {
-	unsigned long nr_pages = totalram_pages;
-	return min(nr_pages - totalhigh_pages, nr_pages / 2);
+	unsigned long nr_pages = totalram_pages();
+
+	return min(nr_pages - totalhigh_pages(), nr_pages / 2);
 }
 #endif
 
@@ -3302,7 +3303,7 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
 			size = memparse(value,&rest);
 			if (*rest == '%') {
 				size <<= PAGE_SHIFT;
-				size *= totalram_pages;
+				size *= totalram_pages();
 				do_div(size, 100);
 				rest++;
 			}