Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262031AbUD1UPj (ORCPT ); Wed, 28 Apr 2004 16:15:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262035AbUD1UPU (ORCPT ); Wed, 28 Apr 2004 16:15:20 -0400 Received: from nn2.excitenetwork.com ([207.159.120.56]:8467 "EHLO excite.com") by vger.kernel.org with ESMTP id S262031AbUD1UOJ (ORCPT ); Wed, 28 Apr 2004 16:14:09 -0400 To: linux-kernel@vger.kernel.org Subject: How can I allocate few bytes to a file to store info about that file? X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: ID = ce179fefc057f62eef8bd4d0182cc843 Reply-To: vintya@excite.com From: "Vineet Joglekar" MIME-Version: 1.0 X-Mailer: PHP Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <20040428201405.5CC7EC01E@xprdmailfe13.nwk.excite.com> Date: Wed, 28 Apr 2004 16:14:05 -0400 (EDT) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2131 Lines: 27 Hi all, I was going through the functions like generic_file_write, generic_file_direct_IO, generic_direct_IO and filemap_fdatasync. I was thinking about calling these functions or calling functions written on similar lines to add new few bytes to the file when the inode is created by "ext2_create()". Can any1 please tell me how to do this? What I mean is, I want to add few bytes to the file as soon as it is created. I want to store some information regarding the file in that area. I guess it would have been simpler to call these functions in the call sys_open() when a new file is created, but I want to make changes in kernel code only in ext2 module. playing with sys_open will be like modifying kernel code apart from the ext2 fs module which I dont want. Thanks and regards, Vineet --- On Mon 04/26, Vineet Joglekar < vintya@excite.com > wrote: From: Vineet Joglekar [mailto: vintya@excite.com] To: linux-fsf@vger.kernel.org Date: Mon, 26 Apr 2004 10:31:19 -0400 Subject: Can I allocate few bytes in a file to store info about that file; not visible to user? Hi all,

In ext2fs, while creating a file, can I allocate a number of bytes for that file in advance, such that those bytes are not seen by the user? that is,

suppose I am creating a new file temp, then allocate 50 bytes immediately after creating the file. I want to use those bytes to store the file related info; accessible only to kernel. Whatever data user wants to add, will be added after the these 50 bytes. If user does lseek(fd,0,SEEK_SET), then the file pointer should point to the 51st byte. The 1st 50 bytes shouldnt be visible to user. I dont care if the file size is shown as userdata+50. Is it possible to achieve? If yes, how?

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