mm/page_ref: use page_ref helper instead of direct modification of _count

page_reference manipulation functions are introduced to track down
reference count change of the page.  Use it instead of direct
modification of _count.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Sunil Goutham <sgoutham@cavium.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/net/wireless/util.c b/net/wireless/util.c
index 219bd19..4e809e9 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -651,7 +651,7 @@
 	struct skb_shared_info *sh = skb_shinfo(skb);
 	int page_offset;
 
-	atomic_inc(&page->_count);
+	page_ref_inc(page);
 	page_offset = ptr - page_address(page);
 	skb_add_rx_frag(skb, sh->nr_frags, page, page_offset, len, size);
 }