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>

1 files changed, 11 insertions, 9 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4b5c4ff68f18..eb2027892ef9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -16,6 +16,7 @@
 
 #include <linux/stddef.h>
 #include <linux/mm.h>
+#include <linux/highmem.h>
 #include <linux/swap.h>
 #include <linux/interrupt.h>
 #include <linux/pagemap.h>
@@ -124,7 +125,8 @@ EXPORT_SYMBOL(node_states);
 /* Protect totalram_pages and zone->managed_pages */
 static DEFINE_SPINLOCK(managed_page_count_lock);
 
-unsigned long totalram_pages __read_mostly;
+atomic_long_t _totalram_pages __read_mostly;
+EXPORT_SYMBOL(_totalram_pages);
 unsigned long totalreserve_pages __read_mostly;
 unsigned long totalcma_pages __read_mostly;
 
@@ -4747,11 +4749,11 @@ EXPORT_SYMBOL_GPL(si_mem_available);
 
 void si_meminfo(struct sysinfo *val)
 {
-	val->totalram = totalram_pages;
+	val->totalram = totalram_pages();
 	val->sharedram = global_node_page_state(NR_SHMEM);
 	val->freeram = global_zone_page_state(NR_FREE_PAGES);
 	val->bufferram = nr_blockdev_pages();
-	val->totalhigh = totalhigh_pages;
+	val->totalhigh = totalhigh_pages();
 	val->freehigh = nr_free_highpages();
 	val->mem_unit = PAGE_SIZE;
 }
@@ -7077,10 +7079,10 @@ void adjust_managed_page_count(struct page *page, long count)
 {
 	spin_lock(&managed_page_count_lock);
 	atomic_long_add(count, &page_zone(page)->managed_pages);
-	totalram_pages += count;
+	totalram_pages_add(count);
 #ifdef CONFIG_HIGHMEM
 	if (PageHighMem(page))
-		totalhigh_pages += count;
+		totalhigh_pages_add(count);
 #endif
 	spin_unlock(&managed_page_count_lock);
 }
@@ -7123,9 +7125,9 @@ EXPORT_SYMBOL(free_reserved_area);
 void free_highmem_page(struct page *page)
 {
 	__free_reserved_page(page);
-	totalram_pages++;
+	totalram_pages_inc();
 	atomic_long_inc(&page_zone(page)->managed_pages);
-	totalhigh_pages++;
+	totalhigh_pages_inc();
 }
 #endif
 
@@ -7174,10 +7176,10 @@ void __init mem_init_print_info(const char *str)
 		physpages << (PAGE_SHIFT - 10),
 		codesize >> 10, datasize >> 10, rosize >> 10,
 		(init_data_size + init_code_size) >> 10, bss_size >> 10,
-		(physpages - totalram_pages - totalcma_pages) << (PAGE_SHIFT - 10),
+		(physpages - totalram_pages() - totalcma_pages) << (PAGE_SHIFT - 10),
 		totalcma_pages << (PAGE_SHIFT - 10),
 #ifdef	CONFIG_HIGHMEM
-		totalhigh_pages << (PAGE_SHIFT - 10),
+		totalhigh_pages() << (PAGE_SHIFT - 10),
 #endif
 		str ? ", " : "", str ? str : "");
 }