From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH 2/2 v2] debugfs: dump a sparse file as a new sparse file Date: Tue, 1 Jan 2013 15:38:58 -0500 Message-ID: <20130101203858.GB12554@thunk.org> References: <1357043415-24668-1-git-send-email-wenqing.lz@taobao.com> <1357043415-24668-3-git-send-email-wenqing.lz@taobao.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, George Spelvin , Zheng Liu To: Zheng Liu Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:41224 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751460Ab3AAUjD (ORCPT ); Tue, 1 Jan 2013 15:39:03 -0500 Content-Disposition: inline In-Reply-To: <1357043415-24668-3-git-send-email-wenqing.lz@taobao.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Jan 01, 2013 at 08:30:15PM +0800, Zheng Liu wrote: > +errcode_t ext2fs_file_read2(ext2_file_t file, void *buf, > + unsigned int wanted, unsigned int *got, > + ext2_off64_t *seek) I'm a bit concenred about this abstraction. Consider what happens if wanted is greater than a block size --- for example, consider if wanted is 16k, and every other 1k block is uninitialized. Then ext2fs_file_read2() will return *got set to 8k, and *seek set to 8k, and the buffer will contain the blocks that are initialized packed up right against each other. Worse, ext2fs_file_read() will do the same thing, so this commit changes how ext2fs_file_read() functions, and a program which expects to get the correct contents from the file will malfunction. - Ted