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/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c
index c1e599a..e065594 100644
--- a/drivers/parisc/sba_iommu.c
+++ b/drivers/parisc/sba_iommu.c
@@ -1414,7 +1414,7 @@ sba_ioc_init(struct parisc_device *sba, struct ioc *ioc, int ioc_num)
 	** for DMA hints - ergo only 30 bits max.
 	*/
 
-	iova_space_size = (u32) (totalram_pages/global_ioc_cnt);
+	iova_space_size = (u32) (totalram_pages()/global_ioc_cnt);
 
 	/* limit IOVA space size to 1MB-1GB */
 	if (iova_space_size < (1 << (20 - PAGE_SHIFT))) {
@@ -1439,7 +1439,7 @@ sba_ioc_init(struct parisc_device *sba, struct ioc *ioc, int ioc_num)
 	DBG_INIT("%s() hpa 0x%lx mem %ldMB IOV %dMB (%d bits)\n",
 			__func__,
 			ioc->ioc_hpa,
-			(unsigned long) totalram_pages >> (20 - PAGE_SHIFT),
+			(unsigned long) totalram_pages() >> (20 - PAGE_SHIFT),
 			iova_space_size>>20,
 			iov_order + PAGE_SHIFT);