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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 92087C33CAF for ; Thu, 16 Jan 2020 19:09:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6613F206E6 for ; Thu, 16 Jan 2020 19:09:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=intel-com.20150623.gappssmtp.com header.i=@intel-com.20150623.gappssmtp.com header.b="J79PjTiw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437390AbgAPTJS (ORCPT ); Thu, 16 Jan 2020 14:09:18 -0500 Received: from mail-oi1-f196.google.com ([209.85.167.196]:46513 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388119AbgAPTJM (ORCPT ); Thu, 16 Jan 2020 14:09:12 -0500 Received: by mail-oi1-f196.google.com with SMTP id 13so19824324oij.13 for ; Thu, 16 Jan 2020 11:09:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6nsG4OiSI74VDUNjgH/EGPUC6QzQOOzMAIB017xQliU=; b=J79PjTiwui87Gtdaft875ciI4awf5xIZ2OlEVeWr6PK1j7HDrzdets/eOiB9gFbjxU N8a+VDYTOh/zAoGUZWE4w1cYgXKFMyIY5mxDDqaoQWFa6T9HxfH2fP9PLUP1uKEVP7xo SFvhifCBTkknEhBzZWrz1h+yDcMOzcy1CAiSWM1LLzIaCNgg2JOGV1Bsk6VwLRFyGzsl 3oI19Df8dP3bwMD1fbOXbUBm44Ixpu94cRB2oRYOQ/+C0gKdgTy/EpALksKs5ue92Nlt bvnoL/8n6PK1nwQDhUpD7aFZSXwTnAcIEDKECZAVt2HboWTI3XccHsyHaJHIW0AO8xHe C2gg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6nsG4OiSI74VDUNjgH/EGPUC6QzQOOzMAIB017xQliU=; b=CsRu2g7814WwqSf1nTcZ6gOU3Th1DEalGAUyIJ1n93OmV/PfSJmZMjyXSdg0nB7TJ+ T8iia8gR6DOZAqlDSFMz08+y3SIiTJMdgxUOAtl6QHCp2SK2z1CTf9UCqGMX+0Wg9PPq tjSdBgaJroy0QJLv6ZTghmFg5jdSV612UosuC2gx2wGbYsHx7VEXFrokCQx49gP75NkV hK5L72/hjv+YVv9ztw9yvPONj2/zDWhI4suwQHWHad0BmdjPygPiBVSibNo/89MIGZgh cwjSala56vhN2bsytGwa7nURrb3OI3KoncPXhaFgcxhoTzOjepuFswHDuOdX2KdIlri2 LXSw== X-Gm-Message-State: APjAAAWwZ4WKkMwd0lC8jaa7VgKOiIdelycp8CvvR2NgGDM2mm77Bz0C vaQPWNUt5raA1+opta/q5SzU/V38W7ghEjdLefuqKw== X-Google-Smtp-Source: APXvYqxWT+/8vZf0zWr1Yl/badv1TRvP/1k5BqWSq6/+HNdAxAD63JMtXrBctEvUY7L00GT1BthDGiNYcFZ4grHpWxY= X-Received: by 2002:aca:3f54:: with SMTP id m81mr427008oia.73.1579201751684; Thu, 16 Jan 2020 11:09:11 -0800 (PST) MIME-Version: 1.0 References: <20200109112447.GG27035@quack2.suse.cz> <20200114203138.GA3145@redhat.com> <20200114212805.GB3145@redhat.com> <20200115195617.GA4133@redhat.com> <20200116183900.GC25291@redhat.com> In-Reply-To: <20200116183900.GC25291@redhat.com> From: Dan Williams Date: Thu, 16 Jan 2020 11:09:00 -0800 Message-ID: Subject: Re: [PATCH 01/19] dax: remove block device dependencies To: Vivek Goyal 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 Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 16, 2020 at 10:39 AM Vivek Goyal wrote: > > 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. > > So udev rules will trigger when a /dev/pmemX device shows up and run > kpartx which in turn will create dm-linear devices and device nodes > will show up in /dev/mapper/pmemXpY. > > IOW, /dev/pmemXpY device nodes will be gone. So if any of the scripts or > systemd unit files are depenent on /dev/pmemXpY, these will still be > broken out of the box and will have to be modified to use device nodes > in /dev/mapper/ directory instead. Do I understand it right, Or I missed > the idea completely. No, I'd write the udev rule to create links from /dev/pmemXpY to the /dev/mapper device, and that rule would be gated by a new pmem device attribute to trigger when kpartx needs to run vs the kernel native partitions.