Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753458Ab0ARCNL (ORCPT ); Sun, 17 Jan 2010 21:13:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752855Ab0ARCNJ (ORCPT ); Sun, 17 Jan 2010 21:13:09 -0500 Received: from mail.parknet.co.jp ([210.171.160.6]:35529 "EHLO mail.parknet.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753212Ab0ARCNH (ORCPT ); Sun, 17 Jan 2010 21:13:07 -0500 From: OGAWA Hirofumi To: KAMEZAWA Hiroyuki Cc: Wu Fengguang , Andrew Morton , Al Viro , Heiko Carstens , Christoph Hellwig , LKML , Eric Paris , Nick Piggin , Andi Kleen , David Howells , Jonathan Corbet , Subject: Re: [PATCH 6/6] vfs: introduce FMODE_NEG_OFFSET for allowing negative f_pos References: <20100115013954.311049665@intel.com> <20100115014422.959401729@intel.com> <87bpgurz00.fsf@devron.myhome.or.jp> <20100118091527.7a0e2c6e.kamezawa.hiroyu@jp.fujitsu.com> <87y6jwnrcz.fsf@devron.myhome.or.jp> <20100118102544.3e897525.kamezawa.hiroyu@jp.fujitsu.com> <87pr58kx9o.fsf@devron.myhome.or.jp> <20100118110019.c55ad88a.kamezawa.hiroyu@jp.fujitsu.com> Date: Mon, 18 Jan 2010 11:13:04 +0900 In-Reply-To: <20100118110019.c55ad88a.kamezawa.hiroyu@jp.fujitsu.com> (KAMEZAWA Hiroyuki's message of "Mon, 18 Jan 2010 11:00:19 +0900") Message-ID: <87y6jwjh3j.fsf@devron.myhome.or.jp> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.91 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1173 Lines: 35 KAMEZAWA Hiroyuki writes: > On Mon, 18 Jan 2010 10:38:27 +0900 > OGAWA Hirofumi wrote: > >> KAMEZAWA Hiroyuki writes: >> >> >> So, lseek() returns (uses) it? >> > >> > lseek can return negative value, as far as I know. >> >> Umm..., how do you know the difference of -EOVERFLOW and fpos == -75? >> > > Ah, sorry. I read wrong. > > For /dev/mem, it uses its own lseek function which allows negative f_pos > value. Other usual file system doesn't allow negative f_pos. > > It's ok not to return -EOVEFLOW for /dev/mem because there is no file end. No, no. I think it has the problem. E.g. /dev/mem returns -75 as fpos, so, lseek(2) returns -75 to userland. Then the userland (e.g. glibc) convert it as error. I.e. finally, errno == -75, and lseek(3) returns -1, right? Thanks. -- OGAWA Hirofumi -- 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/