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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 6A8F6C33C8C for ; Tue, 7 Jan 2020 18:01:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4131F20715 for ; Tue, 7 Jan 2020 18:01:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MhzG/3+u" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728476AbgAGSBP (ORCPT ); Tue, 7 Jan 2020 13:01:15 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:55845 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728459AbgAGSBN (ORCPT ); Tue, 7 Jan 2020 13:01:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578420072; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PCioPbrHOnFEeTCk1vgQEdBJULoDBPQbI4x0bUxfuB4=; b=MhzG/3+uZjPRj2Ux8J4t4UYKXQ3fW3qdWjsC/U1rM0rMOsTi5YNymJuLsyTPppXogNlypn LhTIKP/CiTUJgtmNv6qLP8mA6MFT0vJJjMmjbtXTcrjpeqn+mzQxuK7sw2sNvQ2twwjs7+ L4URlrU6Y4Cy+MGY/Ci5rpteItvKEmA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-356-Nxn0akJlOCG4ursA8-8saw-1; Tue, 07 Jan 2020 13:01:08 -0500 X-MC-Unique: Nxn0akJlOCG4ursA8-8saw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 54EC0593A4; Tue, 7 Jan 2020 18:01:07 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.35]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4B58E60C88; Tue, 7 Jan 2020 18:01:02 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id CA8892202E9; Tue, 7 Jan 2020 13:01:01 -0500 (EST) Date: Tue, 7 Jan 2020 13:01:01 -0500 From: Vivek Goyal To: Dan Williams Cc: "Darrick J. Wong" , Christoph Hellwig , Dave Chinner , Miklos Szeredi , linux-nvdimm , Linux Kernel Mailing List , "Dr. David Alan Gilbert" , virtio-fs@redhat.com, Stefan Hajnoczi , linux-fsdevel Subject: Re: [PATCH 01/19] dax: remove block device dependencies Message-ID: <20200107180101.GC15920@redhat.com> References: <20190827163828.GA6859@redhat.com> <20190828065809.GA27426@infradead.org> <20190828175843.GB912@redhat.com> <20190828225322.GA7777@dread.disaster.area> <20191216181014.GA30106@redhat.com> <20200107125159.GA15745@infradead.org> <20200107170731.GA472641@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 07, 2020 at 09:29:17AM -0800, Dan Williams wrote: > On Tue, Jan 7, 2020 at 9:08 AM Darrick J. Wong wrote: > > > > On Tue, Jan 07, 2020 at 06:22:54AM -0800, Dan Williams wrote: > > > On Tue, Jan 7, 2020 at 4:52 AM Christoph Hellwig wrote: > > > > > > > > On Mon, Dec 16, 2019 at 01:10:14PM -0500, Vivek Goyal wrote: > > > > > > Agree. In retrospect it was my laziness in the dax-device > > > > > > implementation to expect the block-device to be available. > > > > > > > > > > > > It looks like fs_dax_get_by_bdev() is an intercept point where a > > > > > > dax_device could be dynamically created to represent the subset range > > > > > > indicated by the block-device partition. That would open up more > > > > > > cleanup opportunities. > > > > > > > > > > Hi Dan, > > > > > > > > > > After a long time I got time to look at it again. Want to work on this > > > > > cleanup so that I can make progress with virtiofs DAX paches. > > > > > > > > > > I am not sure I understand the requirements fully. I see that right now > > > > > dax_device is created per device and all block partitions refer to it. If > > > > > we want to create one dax_device per partition, then it looks like this > > > > > will be structured more along the lines how block layer handles disk and > > > > > partitions. (One gendisk for disk and block_devices for partitions, > > > > > including partition 0). That probably means state belong to whole device > > > > > will be in common structure say dax_device_common, and per partition state > > > > > will be in dax_device and dax_device can carry a pointer to > > > > > dax_device_common. > > > > > > > > > > I am also not sure what does it mean to partition dax devices. How will > > > > > partitions be exported to user space. > > > > > > > > Dan, last time we talked you agreed that partitioned dax devices are > > > > rather pointless IIRC. Should we just deprecate partitions on DAX > > > > devices and then remove them after a cycle or two? > > > > > > That does seem a better plan than trying to force partition support > > > where it is not needed. > > > > Question: if one /did/ have a partitioned DAX device and used kpartx to > > create dm-linear devices for each partition, will DAX still work through > > that? > > The device-mapper support will continue, but it will be limited to > whole device sub-components. I.e. you could use kpartx to carve up > /dev/pmem0 and still have dax, but not partitions of /dev/pmem0. So we can't use fdisk/parted to partition /dev/pmem0. Given /dev/pmem0 is a block device, I thought tools will expect it to be partitioned. Sometimes I create those partitions and use /dev/pmem0. So what's the replacement for this. People often have tools/scripts which might want to partition the device and these will start failing. IOW, I do not understand that why being able to partition /dev/pmem0 (which is a block device from user space point of view), is pointless. Thanks Vivek