From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p7KGcxAt163376 for ; Sat, 20 Aug 2011 11:38:59 -0500 Received: from mail-ww0-f41.google.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 82A59F8DFD for ; Sat, 20 Aug 2011 09:38:58 -0700 (PDT) Received: from mail-ww0-f41.google.com (mail-ww0-f41.google.com [74.125.82.41]) by cuda.sgi.com with ESMTP id BBqyPtsPqvdB6SBX for ; Sat, 20 Aug 2011 09:38:58 -0700 (PDT) Received: by wwj26 with SMTP id 26so1251939wwj.2 for ; Sat, 20 Aug 2011 09:38:57 -0700 (PDT) Message-ID: <4E4FE1B1.7010601@gmail.com> Date: Sat, 20 Aug 2011 18:32:49 +0200 From: Marco Stornelli MIME-Version: 1.0 Subject: Re: [PATCH 1/4] fs: add SEEK_HOLE and SEEK_DATA flags References: <1309275199-10801-1-git-send-email-josef@redhat.com> <4E4F814B.5070202@gmail.com> <4E4F865B.2010608@gmail.com> <4E4FD48B.8030101@oracle.com> In-Reply-To: <4E4FD48B.8030101@oracle.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Sunil Mushran Cc: linux-kernel@vger.kernel.org, Josef Bacik , xfs@oss.sgi.com, viro@ZenIV.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org Il 20/08/2011 17:36, Sunil Mushran ha scritto: > On 08/20/2011 03:03 AM, Marco Stornelli wrote: >> Il 20/08/2011 11:41, Marco Stornelli ha scritto: >>> Hi, >>> >>> Il 28/06/2011 17:33, Josef Bacik ha scritto: >>>> This just gets us ready to support the SEEK_HOLE and SEEK_DATA flags. >>>> Turns out >>>> using fiemap in things like cp cause more problems than it solves, so >>>> lets try >>>> and give userspace an interface that doesn't suck. We need to match >>>> solaris >>>> here, and the definitions are >>>> >>>> *o* If /whence/ is SEEK_HOLE, the offset of the start of the >>>> next hole greater than or equal to the supplied offset >>>> is returned. The definition of a hole is provided near >>>> the end of the DESCRIPTION. >>>> >>>> *o* If /whence/ is SEEK_DATA, the file pointer is set to the >>>> start of the next non-hole file region greater than or >>>> equal to the supplied offset. >>>> >>> >>> I'm implementing the SEEK_DATA/SEEK_HOLE management for pramfs and I've >>> got some doubts about the right behavior: >>> >>> 1) when we use SEEK_DATA/SEEK_HOLE, the offset used in lseek means >>> always the offset from the start of the file, right? >>> >>> 2) in case of a file with hole at the beginning and data at the end, if >>> I do lseek(fd, 0, SEEK_HOLE) I should receive the end of the file >>> because the idea is to search the *next* hole and we have always a >>> virtual hole at the end of the file, right? >> >> Just to be precise about this question: the alternative here, it's to >> return the same position because we are already in a hole. > > Yes, the offset is from the start of the file. > > And yes, same offset is ok. I think the word next should be > dropped from the definition. It is misleading. > Thank. Yes the word "next" is not very clear. I re-read the proposal for the standard, actually it's seems to me that if we are in the last hole we should return the file size, if we are not in the last hole than it's ok the same offset - "....except that if offset falls beyond the last byte not within a hole, then the file offset may be set to the file size instead". Marco _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs