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, 1 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b4d01969e700..1d2be4c2d34a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -48,7 +48,32 @@ static inline void set_max_mapnr(unsigned long limit)
 static inline void set_max_mapnr(unsigned long limit) { }
 #endif
 
-extern unsigned long totalram_pages;
+extern atomic_long_t _totalram_pages;
+static inline unsigned long totalram_pages(void)
+{
+	return (unsigned long)atomic_long_read(&_totalram_pages);
+}
+
+static inline void totalram_pages_inc(void)
+{
+	atomic_long_inc(&_totalram_pages);
+}
+
+static inline void totalram_pages_dec(void)
+{
+	atomic_long_dec(&_totalram_pages);
+}
+
+static inline void totalram_pages_add(long count)
+{
+	atomic_long_add(count, &_totalram_pages);
+}
+
+static inline void totalram_pages_set(long val)
+{
+	atomic_long_set(&_totalram_pages, val);
+}
+
 extern void * high_memory;
 extern int page_cluster;