zsmalloc: change return value unit of zs_get_total_size_bytes

zs_get_total_size_bytes returns a amount of memory zsmalloc consumed with
*byte unit* but zsmalloc operates *page unit* rather than byte unit so
let's change the API so benefit we could get is that reduce unnecessary
overhead (ie, change page unit with byte unit) in zsmalloc.

Since return type is pages, "zs_get_total_pages" is better than
"zs_get_total_size_bytes".

Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: <juno.choi@lge.com>
Cc: <seungho1.park@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: David Horner <ds2horner@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/zsmalloc.c

@@ -297,7 +297,7 @@ static void zs_zpool_unmap(void *pool, unsigned long handle)
 
 static u64 zs_zpool_total_size(void *pool)
 {
-	return zs_get_total_size_bytes(pool);
+	return zs_get_total_pages(pool) << PAGE_SHIFT;
 }
 
 static struct zpool_driver zs_zpool_driver = {
@@ -1181,12 +1181,11 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
 }
 EXPORT_SYMBOL_GPL(zs_unmap_object);
 
-u64 zs_get_total_size_bytes(struct zs_pool *pool)
+unsigned long zs_get_total_pages(struct zs_pool *pool)
 {
-	u64 npages = atomic_long_read(&pool->pages_allocated);
-	return npages << PAGE_SHIFT;
+	return atomic_long_read(&pool->pages_allocated);
 }
-EXPORT_SYMBOL_GPL(zs_get_total_size_bytes);
+EXPORT_SYMBOL_GPL(zs_get_total_pages);
 
 module_init(zs_init);
 module_exit(zs_exit);