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=-5.2 required=3.0 tests=BAYES_00, 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 1948AC4743C for ; Wed, 23 Jun 2021 07:21:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB53A6102A for ; Wed, 23 Jun 2021 07:21:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229913AbhFWHYA (ORCPT ); Wed, 23 Jun 2021 03:24:00 -0400 Received: from verein.lst.de ([213.95.11.211]:49632 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229660AbhFWHX7 (ORCPT ); Wed, 23 Jun 2021 03:23:59 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 409B567373; Wed, 23 Jun 2021 09:21:40 +0200 (CEST) Date: Wed, 23 Jun 2021 09:21:40 +0200 From: Christoph Hellwig To: Coly Li Cc: Christoph Hellwig , "Huang, Ying" , Dan Williams , Jan Kara , Hannes Reinecke , linux-bcache@vger.kernel.org, linux-block@vger.kernel.org, Jianpeng Ma , Qiaowei Ren , axboe@kernel.dk Subject: Re: Ask help for code review (was Re: [PATCH 03/14] bcache: add initial data structures for nvm pages) Message-ID: <20210623072140.GA837@lst.de> References: <20210615054921.101421-1-colyli@suse.de> <20210615054921.101421-4-colyli@suse.de> <24ad3795-813c-b50b-e983-56dccef1b0db@suse.de> <875yy6l2a1.fsf@yhuang6-desk2.ccr.corp.intel.com> <87czsdhy0u.fsf@yhuang6-desk2.ccr.corp.intel.com> <20210623070405.GA537@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On Wed, Jun 23, 2021 at 03:19:11PM +0800, Coly Li wrote: > Bcache does not support endian clean indeed, Then we need to fix that eventually rather than making it worse. Which means any _new_ data structure should start that way. > and libnvdimm only works with > 64bit physical address width. Maybe it does right now. But ther is nothing fundamental in that, so please don't design stupid on-disk formats to encode that are going to come back to bite us sooner or later. Be that by adding 32-bit support for any Linux DAX device, or by new 96 or 128bit CPUs. > The only restriction here by using pointer is > the CPU register word should be 64bits, because we use the NVDIMM as memory. > > Is it one of the way how NVDIMM (especially Intel AEP) designed to use ? > As a non-volatiled memory. Not for on-disk data structures. > Does the already mapped DAX base address change in runtime during memory > hot plugable ? > If not, it won't be a problem here for this specific use case. It could change between one use and another.