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 B6D10C352A3 for ; Tue, 11 Feb 2020 17:33:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E7E5214DB for ; Tue, 11 Feb 2020 17:33:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Xw063yE2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729644AbgBKRdl (ORCPT ); Tue, 11 Feb 2020 12:33:41 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:29182 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729031AbgBKRdl (ORCPT ); Tue, 11 Feb 2020 12:33:41 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581442420; 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=4X0xfWONZNxuOkpbq3f8Jv0lG2stok0ct4V7XvEvhEQ=; b=Xw063yE2SCnIEXtG7JmV9n1NJPe6Ju/E3MSdKhWI/MDryAV59UBizO5m+oZ/aVPcFoOMfD LgiPmben91IcjieIMQi2Ms0lYMgAXDgmKaMp/fROz7NXNS3JyEgrqX5VWwdJAYojlU+sy8 3X9EACDHaj2dMTulEoRR7WXjzWHhmBE= 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-28-h0GrCcpQOAi3KCxts--_oA-1; Tue, 11 Feb 2020 12:33:38 -0500 X-MC-Unique: h0GrCcpQOAi3KCxts--_oA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 391D9100550E; Tue, 11 Feb 2020 17:33:37 +0000 (UTC) Received: from horse.redhat.com (ovpn-123-66.rdu2.redhat.com [10.10.123.66]) by smtp.corp.redhat.com (Postfix) with ESMTP id C807D26FB2; Tue, 11 Feb 2020 17:33:31 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 4579E220A24; Tue, 11 Feb 2020 12:33:31 -0500 (EST) Date: Tue, 11 Feb 2020 12:33:31 -0500 From: Vivek Goyal To: Dan Williams Cc: Jeff Moyer , Jan Kara , "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: <20200211173331.GC8590@redhat.com> References: <20200109112447.GG27035@quack2.suse.cz> <20200114203138.GA3145@redhat.com> <20200114212805.GB3145@redhat.com> <20200115195617.GA4133@redhat.com> 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 2.84 on 10.5.11.23 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Jan 16, 2020 at 10:09:46AM -0800, Dan Williams wrote: > On Wed, Jan 15, 2020 at 1:08 PM Jeff Moyer wrote: > > > > Hi, Dan, > > > > Dan Williams writes: > > > > > I'm going to take a look at how hard it would be to develop a kpartx > > > fallback in udev. If that can live across the driver transition then > > > maybe this can be a non-event for end users that already have that > > > udev update deployed. > > > > I just wanted to remind you that label-less dimms still exist, and are > > still being shipped. For those devices, the only way to subdivide the > > storage is via partitioning. > > True, but if kpartx + udev can make this transparent then I don't > think users lose any functionality. They just gain a device-mapper > dependency. Hi Dan, Are you planning to look into making this work? We can easily disable partition scanning by specifying gendisk GENHD_FL_NO_PART_SCAN flag. But what about partition additiona path, ioctl(BLKPG_ADD_PARTITION). That does not seem to do any checks whether block device supports in kernel partitions or not. So kernel partitions (hence /dev/pmemXpY) objects are created anyway and this will conflict with all the new planned udev rules. If you block ioctl(BLKPG_ADD_PARTITION), then user space tools like parted and fdisk started breaking when trying to create a partition on /dev/pmeme0. IIUC, we have to allow partition table creation on /dev/pmem0 so that later kpartx can parse it and create dm-linear partitions. Thanks Vivek