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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 BA012C28CC3 for ; Fri, 7 Jun 2019 06:00:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 908A220825 for ; Fri, 7 Jun 2019 06:00:55 +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="WfyEYkZe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726795AbfFGGAr (ORCPT ); Fri, 7 Jun 2019 02:00:47 -0400 Received: from mail-ot1-f67.google.com ([209.85.210.67]:36715 "EHLO mail-ot1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726726AbfFGGAr (ORCPT ); Fri, 7 Jun 2019 02:00:47 -0400 Received: by mail-ot1-f67.google.com with SMTP id c3so826981otr.3 for ; Thu, 06 Jun 2019 23:00:47 -0700 (PDT) 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=/KxNQ9MI1VotM1MpZhO1sXWtsUgIvWtrmcpqkBhjppA=; b=WfyEYkZegPTmvynLc2fjjKs6d/TdRZHB2mGyi3svr8A4gfvWp7nBiukv2oNPMrRNu3 LF5pIX9mWCDEYPKHsg9x8FyxTEXL3Pp4DEsbFXvMjA67etlGXIbfY2hNbJLOqw4TuZAK Bxvkt2hCh3F5rpXtMyj2CBZde6MBilulGBAwGobq2TdvBZsm+WUcNaCHcTKujMNYBYzA Jz+YlbRdrvtxV6qQh4bHw4H4UOWvGsLOnQyJmjDAnpMCiSaVTnMqJomtxlE/4a38CErg OEy8Ur6MMHV2bA7bkrmZl08c3aZp2RHd2Dpw55zuwf2rl9TE1d9/sN4lvF3IDzCodhLY IFJw== 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=/KxNQ9MI1VotM1MpZhO1sXWtsUgIvWtrmcpqkBhjppA=; b=syfrsaZ+km6/SoBSOlE0Jm2BZ7fQmPGmBoN/mvGL4/eFcCujw64F6UgLDl1nCdCOyF IQon9uhO3hq/gK/WzuOfzhjDkoTDwCO4jMKmQGlPiqOCPHWVMIDJ1KZNL+PvF3oF/per PS/S2ZYasJxwb3UQ3WlbUO+/szCa0BC8eVYZlg6PrFlFAvB8PYioGnwlB6Wc7LB1hKaR LU4bpik39TUCKGVcKh9npbIkOYg6o849cq6s2cWbYT5C24W7vZ29PAZOmBGm9hFIhPS/ sxRnhnVKSVCqffS0vIwoJsNG5bh0pWSorW1vp8UCTtY4RSAIIX8yt8yI4ABKH7Konilb w1Uw== X-Gm-Message-State: APjAAAWnxUjul5vFAk93BZE07n3D3Uc3olJT8rpLuizNC86rWQjAXhXo 6mOdZSJHUR4rlPcRb5RY3T7X+bCtfVEZB/PsMxWAbg== X-Google-Smtp-Source: APXvYqwgOBlvuuzB4VOYDbIT/0knuoEr43azK6XWvG7H+/gVjkfE0RSOiURNIXMgTP5DMZNdOklRtNkV5jBX8cvgDmo= X-Received: by 2002:a9d:6e96:: with SMTP id a22mr17778966otr.207.1559887246873; Thu, 06 Jun 2019 23:00:46 -0700 (PDT) MIME-Version: 1.0 References: <20190214134622.GG4525@dhcp22.suse.cz> <20190214191013.GA3420@redhat.com> <20190214200840.GB12668@bombadil.infradead.org> <20190605162204.jzou5hry5exly5wx@fiona> In-Reply-To: <20190605162204.jzou5hry5exly5wx@fiona> From: Dan Williams Date: Thu, 6 Jun 2019 23:00:35 -0700 Message-ID: Subject: Re: [Lsf-pc] [LSF/MM TOPIC] The end of the DAX experiment To: Goldwyn Rodrigues Cc: Matthew Wilcox , Jerome Glisse , Michal Hocko , lsf-pc@lists.linux-foundation.org, linux-xfs , linux-fsdevel , linux-ext4 , Linux Kernel Mailing List , linux-nvdimm Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Jun 5, 2019 at 9:22 AM Goldwyn Rodrigues wrote: > > Hi Dan/Jerome, > > On 12:20 14/02, Dan Williams wrote: > > On Thu, Feb 14, 2019 at 12:09 PM Matthew Wilcox wrote: > > > > > > On Thu, Feb 14, 2019 at 11:31:24AM -0800, Dan Williams wrote: > > > > On Thu, Feb 14, 2019 at 11:10 AM Jerome Glisse wrote: > > > > > I am just again working on my struct page mapping patchset as well as > > > > > the generic page write protection that sits on top. I hope to be able > > > > > to post the v2 in couple weeks. You can always look at my posting last > > > > > year to see more details. > > > > > > > > Yes, I have that in mind as one of the contenders. However, it's not > > > > clear to me that its a suitable fit for filesystem-reflink. Others > > > > have floated the 'page proxy' idea, so it would be good to discuss the > > > > merits of the general approaches. > > > > > > ... and my preferred option of putting pfn entries in the page cache. > > > > Another option to include the discussion. > > > > > Or is that what you meant by "page proxy"? > > > > Page proxy would be an object that a filesystem could allocate to > > point back to a single physical 'struct page *'. The proxy would > > contain an override for page->index. > > Was there any outcome on this and its implementation? I am specifically > interested in this for DAX support on btrfs/CoW: The TODO comment on > top of dax_associate_entry() :) > > If there are patches/git tree I could use to base my patches on, it would > be nice. Half joking, but I was hoping that by the time I had circled back to finally reviewing the brtfs dax patches that a solution to this problem would be waiting. We spent more time on other DAX topics. I recall that Jerome and I were mutually skeptical of each others approaches at first glance, but we did not get into the details. So, I think it will be a matter of getting the idea coded up. I'm finally coming out from under a pile of mm work so I should have some time this cycle to push the page proxy idea forward.