zcache: The last of the atomic reads has now an accessory function.

And now we can move the code ([inc|dec]_zcache_[*]) to their own file
with a header to make them nops or feed in debugfs.
Acked-by: NDan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/zcache/zcache-main.c

@@ -253,6 +253,14 @@ static inline void dec_zcache_pers_zpages(unsigned zpages)
 {
 	zcache_pers_zpages = atomic_sub_return(zpages, &zcache_pers_zpages_atomic);
 }
+
+static inline unsigned long curr_pageframes_count(void)
+{
+	return zcache_pageframes_alloced -
+		atomic_read(&zcache_pageframes_freed_atomic) -
+		atomic_read(&zcache_eph_pageframes_atomic) -
+		atomic_read(&zcache_pers_pageframes_atomic);
+};
 /* but for the rest of these, counting races are ok */
 static ssize_t zcache_flush_total;
 static ssize_t zcache_flush_found;
@@ -565,10 +573,7 @@ static void zcache_free_page(struct page *page)
 		BUG();
 	__free_page(page);
 	inc_zcache_pageframes_freed();
-	curr_pageframes = zcache_pageframes_alloced -
-			atomic_read(&zcache_pageframes_freed_atomic) -
-			atomic_read(&zcache_eph_pageframes_atomic) -
-			atomic_read(&zcache_pers_pageframes_atomic);
+	curr_pageframes = curr_pageframes_count();
 	if (curr_pageframes > max_pageframes)
 		max_pageframes = curr_pageframes;
 	if (curr_pageframes < min_pageframes)