[PATCH] vmsplice: restrict stealing a little more

Apply the same rules as the anon pipe pages, only allow stealing
if no one else is using the page.

Signed-off-by: Jens Axboe <axboe@suse.de>

fs/splice.c

@@ -141,7 +141,7 @@ static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 		return 1;
 
-	return 0;
+	return generic_pipe_buf_steal(pipe, buf);
 }
 
 static struct pipe_buf_operations user_page_pipe_buf_ops = {