FS-Cache: wake write waiter after invalidating writes

Signed-off-by: Yan, Zheng <[e-mail]>
Acked-by: David Howells <[e-mail]>

fs/fscache/page.c

···
 			put_page(results[i]);
 	}
 
+	wake_up_bit(&cookie->flags, 0);
+
 	_leave("");
 }