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, 26 insertions, 2 deletions

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 0690679832d4..ea5cdbd8c2c3 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -36,7 +36,31 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
 
 /* declarations for linux/mm/highmem.c */
 unsigned int nr_free_highpages(void);
-extern unsigned long totalhigh_pages;
+extern atomic_long_t _totalhigh_pages;
+static inline unsigned long totalhigh_pages(void)
+{
+        return (unsigned long)atomic_long_read(&_totalhigh_pages);
+}
+
+static inline void totalhigh_pages_inc(void)
+{
+        atomic_long_inc(&_totalhigh_pages);
+}
+
+static inline void totalhigh_pages_dec(void)
+{
+        atomic_long_dec(&_totalhigh_pages);
+}
+
+static inline void totalhigh_pages_add(long count)
+{
+        atomic_long_add(count, &_totalhigh_pages);
+}
+
+static inline void totalhigh_pages_set(long val)
+{
+        atomic_long_set(&_totalhigh_pages, val);
+}
 
 void kmap_flush_unused(void);
 
@@ -51,7 +75,7 @@ static inline struct page *kmap_to_page(void *addr)
         return virt_to_page(addr);
 }
 
-#define totalhigh_pages 0UL
+static inline unsigned long totalhigh_pages(void) { return 0UL; }
 
 #ifndef ARCH_HAS_KMAP
 static inline void *kmap(struct page *page)