Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752443Ab2HSXtg (ORCPT ); Sun, 19 Aug 2012 19:49:36 -0400 Received: from mail-vb0-f46.google.com ([209.85.212.46]:44981 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751616Ab2HSXte (ORCPT ); Sun, 19 Aug 2012 19:49:34 -0400 MIME-Version: 1.0 In-Reply-To: <5030BE93.50909@gmail.com> References: <1345283361-7802-1-git-send-email-linkinjeon@gmail.com> <20120819021757.GB16796@localhost> <5030BE93.50909@gmail.com> Date: Mon, 20 Aug 2012 08:49:33 +0900 Message-ID: Subject: Re: [PATCH 2/3] writeback: fix incorrect return value type of bdi_dirty_limit From: Namjae Jeon To: Marco Stornelli Cc: Fengguang Wu , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1026 Lines: 30 2012/8/19, Marco Stornelli : > Il 19/08/2012 04:17, Fengguang Wu ha scritto: >> On Sat, Aug 18, 2012 at 05:49:21AM -0400, Namjae Jeon wrote: >>> unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long >>> dirty) >>> >>> Above function return type is unsigned long, but return value is >>> kept in "u64 bdi_dirty". >>> It can return incorrect value by type casting. >> >> I don't see how the cast can return wrong value. >> The u64 is necessary for the intermediate calculations. >> >> Thanks, >> Fengguang >> > > We are sure u64 is 8byte long, but unsigned long is 4byte long on 32-bit > machine, so if bdi_dirty can assume values bigger than 2^32 there is an > implicit truncate of its value, isn't it? Yes, right. Thanks. > > Marco > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/