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: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: NVlastimil 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/net/ethernet/cavium/thunder/nicvf_queues.c

@@ -23,7 +23,7 @@ static void nicvf_get_page(struct nicvf *nic)
 	if (!nic->rb_pageref || !nic->rb_page)
 		return;
 
-	atomic_add(nic->rb_pageref, &nic->rb_page->_count);
+	page_ref_add(nic->rb_page, nic->rb_pageref);
 	nic->rb_pageref = 0;
 }
 

drivers/net/ethernet/qlogic/qede/qede_main.c

@@ -920,7 +920,7 @@ static inline int qede_realloc_rx_buffer(struct qede_dev *edev,
 		 * network stack to take the ownership of the page
 		 * which can be recycled multiple times by the driver.
 		 */
-		atomic_inc(&curr_cons->data->_count);
+		page_ref_inc(curr_cons->data);
 		qede_reuse_page(edev, rxq, curr_cons);
 	}
 

mm/filemap.c

@@ -213,7 +213,7 @@ void __delete_from_page_cache(struct page *page, void *shadow)
 			 * some other bad page check should catch it later.
 			 */
 			page_mapcount_reset(page);
-			atomic_sub(mapcount, &page->_count);
+			page_ref_sub(page, mapcount);
 		}
 	}
 

net/wireless/util.c

@@ -651,7 +651,7 @@ __frame_add_frag(struct sk_buff *skb, struct page *page,
 	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);
 }