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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 30005C33CA2 for ; Fri, 10 Jan 2020 12:36:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0185F20721 for ; Fri, 10 Jan 2020 12:36:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fEApSJol" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728121AbgAJMgg (ORCPT ); Fri, 10 Jan 2020 07:36:36 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:49312 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728010AbgAJMgg (ORCPT ); Fri, 10 Jan 2020 07:36:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=f/42qAPbVsW+72MUlq6/DiKhzWxy8T8Hdkwap/qT96A=; b=fEApSJolHaXmpdLYBb+Kkv8Df BGQz3JHJbvpYxwghgcQ6w2GqDx37gBdlNAcBRR2IhHq7bLXUI0kKJMEKsa0vIsqtORSOf/CH4cE5T Xwsj1uGAQtxR/yLpUOSiwVEBEYdzPgHAUs1ofiX1hdTQu1EHvg1Xy/6nf0/BV6/6Z1co1P+6cHxk4 Xnqyp0cPEwm83h6/DTRS+riPEzRcEw3vnnEH/NSQGzCNmLwpBofZFEikltSBx+l2HJgHLATqQTKvr Z23nhy3IejVYasyMnB5v/3udsJnqEdFD3lfUFeQnEoms+RUyXa2IO2K0GKHmbFdvlPMuh4SZezxpr LkSZT0k7A==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iptWh-0006RF-VG; Fri, 10 Jan 2020 12:36:31 +0000 Date: Fri, 10 Jan 2020 04:36:31 -0800 From: Christoph Hellwig To: Dan Williams Cc: 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: <20200110123631.GA16268@infradead.org> References: <20200107125159.GA15745@infradead.org> <20200107170731.GA472641@magnolia> <20200107180101.GC15920@redhat.com> <20200107183307.GD15920@redhat.com> <20200109112447.GG27035@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Jan 09, 2020 at 12:03:01PM -0800, Dan Williams wrote: > > So I'd find two options reasonably consistent: > > 1) Keep status quo where partitions are created and support DAX. > > 2) Stop partition creation altogether, if anyones wants to split pmem > > device further, he can use dm-linear for that (i.e., kpartx). > > > > But I'm not sure if the ship hasn't already sailed for option 2) to be > > feasible without angry users and Linus reverting the change. > > Christoph? I feel myself leaning more and more to the "keep pmem > partitions" camp. > > I don't see "drop partition support" effort ending well given the long > standing "ext4 fails to mount when dax is not available" precedent. Do we have any evidence of existing setups with DAX and partitions? Can we just throw in a patch to reject that case for now before actually removing the code and see if anyone screams. And fix ext4 up while we are at it. > I think the next least bad option is to have a dax_get_by_host() > variant that passes an offset and length pair rather than requiring a > later bdev_dax_pgoff() to recall the offset. This also prevents > needing to add another dax-device object representation. IFF we have to keep partition support, yes. But keeping it just seems like a really bad idea.