Now that XFS is no longer using find_trylock_page, the interface can
be easily changed so as to take a reference as well. This looks
questionable now, but streamlines the lockless implementation.

Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c
@@ -534,7 +534,7 @@ struct page * find_get_page(struct addre
 EXPORT_SYMBOL(find_get_page);
 
 /*
- * Same as above, but trylock it instead of incrementing the count.
+ * Same as above, but trylock it as well.
  */
 struct page *find_trylock_page(struct address_space *mapping, unsigned long offset)
 {
@@ -542,8 +542,12 @@ struct page *find_trylock_page(struct ad
 
 	read_lock_irq(&mapping->tree_lock);
 	page = radix_tree_lookup(&mapping->page_tree, offset);
-	if (page && TestSetPageLocked(page))
-		page = NULL;
+	if (page) {
+		if (unlikely(TestSetPageLocked(page)))
+			page = NULL;
+		else
+			get_page(page);
+	}
 	read_unlock_irq(&mapping->tree_lock);
 	return page;
 }
Index: linux-2.6/mm/swapfile.c
===================================================================
--- linux-2.6.orig/mm/swapfile.c
+++ linux-2.6/mm/swapfile.c
@@ -402,7 +402,6 @@ void free_swap_and_cache(swp_entry_t ent
 	}
 	if (page) {
 		BUG_ON(PagePrivate(page));
-		page_cache_get(page);
 		/* No users, or swap space full? Free it! */
 		if (!PageWriteback(page) &&
 				(page_mapcount(page) == 0 || vm_swap_full())) {