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 6C75FC33CB8 for ; Thu, 16 Jan 2020 19:24:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46CCC207FF for ; Thu, 16 Jan 2020 19:24:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VcEOirFK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389580AbgAPTYG (ORCPT ); Thu, 16 Jan 2020 14:24:06 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:51890 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731007AbgAPTYF (ORCPT ); Thu, 16 Jan 2020 14:24:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579202644; 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=e8HBHJP/uq6LLcUiW9DMmgfjF72wvEE4C0oRW83XDZw=; b=VcEOirFKhZ/qGMHCRLahr+bltd2l1gTxwfk5EDwDmKEoDSyWqgJEWy7o1n6L7SEvhvykxz hE6uzNQaU+jZx3E9qOdEBE1+E1NV4ECevJvap0VSJnxtEuADcPMLB5NyAcL/q8EG4JOPuC FWwffG4wDRPc+hjx2L9hdGdZ7pPsrdQ= 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-246-Wpe1cMcoOoGBY_oRiv4oYg-1; Thu, 16 Jan 2020 14:24:00 -0500 X-MC-Unique: Wpe1cMcoOoGBY_oRiv4oYg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 119012F2E; Thu, 16 Jan 2020 19:23:59 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.35]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3BC035D9C9; Thu, 16 Jan 2020 19:23:54 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id C1B6B220A24; Thu, 16 Jan 2020 14:23:53 -0500 (EST) Date: Thu, 16 Jan 2020 14:23:53 -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: <20200116192353.GD25291@redhat.com> References: <20200114203138.GA3145@redhat.com> <20200114212805.GB3145@redhat.com> <20200115195617.GA4133@redhat.com> <20200116183900.GC25291@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 2.79 on 10.5.11.14 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 11:09:00AM -0800, Dan Williams wrote: [..] > > > 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. Got it. This sounds much better. Vivek