From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D659C433FF for ; Thu, 8 Aug 2019 08:40:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 26F35214C6 for ; Thu, 8 Aug 2019 08:40:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731187AbfHHIkj (ORCPT ); Thu, 8 Aug 2019 04:40:39 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:3083 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726187AbfHHIki (ORCPT ); Thu, 8 Aug 2019 04:40:38 -0400 Received: from DGGEMM404-HUB.china.huawei.com (unknown [172.30.72.55]) by Forcepoint Email with ESMTP id F0C7E64C495EF3C2A2DF; Thu, 8 Aug 2019 16:40:36 +0800 (CST) Received: from dggeme762-chm.china.huawei.com (10.3.19.108) by DGGEMM404-HUB.china.huawei.com (10.3.20.212) with Microsoft SMTP Server (TLS) id 14.3.439.0; Thu, 8 Aug 2019 16:40:36 +0800 Received: from 138 (10.175.124.28) by dggeme762-chm.china.huawei.com (10.3.19.108) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1591.10; Thu, 8 Aug 2019 16:40:36 +0800 Date: Thu, 8 Aug 2019 16:57:45 +0800 From: Gao Xiang To: Dave Chinner CC: Goldwyn Rodrigues , "hch@lst.de" , "darrick.wong@oracle.com" , "linux-btrfs@vger.kernel.org" , "ruansy.fnst@cn.fujitsu.com" , "linux-fsdevel@vger.kernel.org" , , Subject: Re: [PATCH 10/13] iomap: use a function pointer for dio submits Message-ID: <20190808085745.GE28630@138> References: <20190802220048.16142-1-rgoldwyn@suse.de> <20190802220048.16142-11-rgoldwyn@suse.de> <20190804234321.GC7689@dread.disaster.area> <1565021323.13240.14.camel@suse.com> <20190805215458.GH7689@dread.disaster.area> <20190808042640.GA28630@138> <20190808054936.GA5319@sol.localdomain> <20190808081647.GI7689@dread.disaster.area> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20190808081647.GI7689@dread.disaster.area> User-Agent: Mutt/1.11.3 (2019-02-01) X-Originating-IP: [10.175.124.28] X-ClientProxiedBy: dggeme704-chm.china.huawei.com (10.1.199.100) To dggeme762-chm.china.huawei.com (10.3.19.108) X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hi Dave, On Thu, Aug 08, 2019 at 06:16:47PM +1000, Dave Chinner wrote: > On Wed, Aug 07, 2019 at 10:49:36PM -0700, Eric Biggers wrote: > > FWIW, the only order that actually makes sense is decrypt->decompress->verity. > > *nod* > > Especially once we get the inline encryption support for fscrypt so > the storage layer can offload the encrypt/decrypt to hardware via > the bio containing plaintext. That pretty much forces fscrypt to be > the lowest layer of the filesystem transformation stack. This > hardware offload capability also places lots of limits on what you > can do with block-based verity layers below the filesystem. e.g. > using dm-verity when you don't know if there's hardware encryption > below or software encryption on top becomes problematic... > > So really, from a filesystem and iomap perspective, What Eric says > is the right - it's the only order that makes sense... Don't be surprised there will be a decrypt/verity/decompress all-in-one hardware approach for such stuff. 30% random IO (no matter hardware or software approach) can be saved that is greatly helpful for user experience on embedded devices with too limited source. and I really got a SHA256 CPU hardware bug years ago. I don't want to talk more on tendency, it depends on real scenerio and user selection (server or embedded device). For security consideration, these approaches are all the same level --- these approaches all from the same signed key and storage source, all transformation A->B->C or A->C->B are equal. For bug-free, we can fuzzer compression/verity algorithms even the whole file-system stack. There is another case other than security consideration. Thanks, Gao Xiang > > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com