From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266124AbUBQMAr (ORCPT ); Tue, 17 Feb 2004 07:00:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266145AbUBQMAq (ORCPT ); Tue, 17 Feb 2004 07:00:46 -0500 Received: from gprs155-60.eurotel.cz ([160.218.155.60]:47233 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S266124AbUBQMAp (ORCPT ); Tue, 17 Feb 2004 07:00:45 -0500 Date: Tue, 17 Feb 2004 13:00:21 +0100 From: Pavel Machek To: Robert White Cc: "'Theodore Ts'o'" , "'the grugq'" , linux-kernel@vger.kernel.org Subject: Re: PATCH - ext2fs privacy (i.e. secure deletion) patch Message-ID: <20040217120021.GB392@elf.ucw.cz> References: <20040204062936.GA2663@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > At which point, in the presence of the theoretical mount option, it becomes > easy to reduce the work load to "a long list of block operations" by making > the shredding unconditional. > > That is, instead of thinking of it as shredding a file, the (arbitrarily > named) "zerofree" mount option is passed and every block that is released > from active file system use is zeroed. E.g. file blocks, directory blocks, > attribute blocks, everything. That just takes (at the worst) a list/queue > and a block-write of a block-sized page containing all zeros (or, better > yet, an optionally-user-supplied squeegee pattern.) So take/make the > free_block() routine and make it submit a "dirty block" to the I/O buffering > system. If the block is immediately re-used then even the write expense > amortizes to near zero for clearing that block (or unwritten > fragment). I see a small problem with that: some "interesting" data, such as file names, are smaller than a block. With this kind of implementation, you'd never wipe those. Pavel [un-erase no longer works even on ext3, that's nothing new] -- When do you have a heart between your knees? [Johanka's followup: and *two* hearts?]