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=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 ABEC5C04EB9 for ; Wed, 5 Dec 2018 05:53:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DBBA20672 for ; Wed, 5 Dec 2018 05:53:09 +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="ceMEcUYA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6DBBA20672 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726990AbeLEFxI (ORCPT ); Wed, 5 Dec 2018 00:53:08 -0500 Received: from mail-oi1-f193.google.com ([209.85.167.193]:38609 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726092AbeLEFxI (ORCPT ); Wed, 5 Dec 2018 00:53:08 -0500 Received: by mail-oi1-f193.google.com with SMTP id a77so16522895oii.5 for ; Tue, 04 Dec 2018 21:53:07 -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=VSZQnPI0FBoEqglt9fZ3DmEr6tIcOBET7Whd6RBYZ2c=; b=ceMEcUYACj06PrSERxWENhlZxTZgy0iZFPghHZybh+9VoOmxEJeCgZtbwQp80l75ui TyxS4Qr7AYQMq1HKE/+S4Ha3oaJg8SA6cSifbtNskDL9pKxRmsqiZqIe6HvXZgmhp8eX XffBUg2Aq7Ob/ooEEJt4ndIt6pG9bo4AwNiU4r6Qa1va0+5qGXkI3waIVCZSwfsMOMD+ gtVv4SkvjpiCSDPyh7vlPrCexIAhaLgDJivvL4XXfWNEQfausA2bMD9RbXYHF59NXi7s Cpm1a+bEe7pbm2xuSvVNJynHsX1OBvw30ATi+hnBnXmgUqaSQ5t5qvuU2GEM8GcN0UMT yo1Q== 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=VSZQnPI0FBoEqglt9fZ3DmEr6tIcOBET7Whd6RBYZ2c=; b=pjbNT1RoHPZw4XCzvQ3KeY+tyxjCMOY6+V1BD68yIEDe6ZycHr9yN2IiNdOGAq8oza nernBFC0GYOgGwsVFpuuUpemFCze+M8y0Aq4pDIT6WhIofNdjjTQBIK9qc3UheQfum5X vDGL+Hpb+/X3P4IVhUPwAc2T5GhdAw2eNUPeE94REMKFDegdypvVhmTfVmhlKR55Zi6I LsAPzsUEuPeOhtKYOsCx6fbji66UbSsXVcEcH5m5A8wBFs3b3Zz3TBuX2PoGNYXEoitY +tpJ4jSBBTNGA9atTKO6HwOobEsbZ8i2nnYSa52Mki730fy+loE/ZLWhBR3Rz8d+VgLb wCzg== X-Gm-Message-State: AA+aEWYHGpvinxAzNHVm+eQ+G1ZbOL6JouzgAeId6+xZYFdnik2KjZcW P9HN9teJh9qRLLH8kXdZn70wAYm61Ow3/ZJ20CkKIQ== X-Google-Smtp-Source: AFSGD/WaQXDwqfHGL70m5iWhhPfizJ/tKJiZgpXKZG45gD/OxZL2QxUdHmVU1uoNO+uxI+krKeUTPQps7TtYfKsoEwY= X-Received: by 2002:aca:d78b:: with SMTP id o133mr8279595oig.232.1543989186763; Tue, 04 Dec 2018 21:53:06 -0800 (PST) MIME-Version: 1.0 References: <20181204001720.26138-1-jhubbard@nvidia.com> <20181204001720.26138-2-jhubbard@nvidia.com> <3c91d335-921c-4704-d159-2975ff3a5f20@nvidia.com> <20181205011519.GV10377@bombadil.infradead.org> In-Reply-To: <20181205011519.GV10377@bombadil.infradead.org> From: Dan Williams Date: Tue, 4 Dec 2018 21:52:54 -0800 Message-ID: Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions To: Matthew Wilcox Cc: John Hubbard , John Hubbard , Andrew Morton , Linux MM , Jan Kara , tom@talpey.com, Al Viro , benve@cisco.com, Christoph Hellwig , Christopher Lameter , "Dalessandro, Dennis" , Doug Ledford , Jason Gunthorpe , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Michal Hocko , mike.marciniszyn@intel.com, rcampbell@nvidia.com, Linux Kernel Mailing List , 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 Tue, Dec 4, 2018 at 5:15 PM Matthew Wilcox wrote: > > On Tue, Dec 04, 2018 at 04:58:01PM -0800, John Hubbard wrote: > > On 12/4/18 3:03 PM, Dan Williams wrote: > > > Except the LRU fields are already in use for ZONE_DEVICE pages... how > > > does this proposal interact with those? > > > > Very badly: page->pgmap and page->hmm_data both get corrupted. Is there an entire > > use case I'm missing: calling get_user_pages() on ZONE_DEVICE pages? Said another > > way: is it reasonable to disallow calling get_user_pages() on ZONE_DEVICE pages? > > > > If we have to support get_user_pages() on ZONE_DEVICE pages, then the whole > > LRU field approach is unusable. > > We just need to rearrange ZONE_DEVICE pages. Please excuse the whitespace > damage: > > +++ b/include/linux/mm_types.h > @@ -151,10 +151,12 @@ struct page { > #endif > }; > struct { /* ZONE_DEVICE pages */ > + unsigned long _zd_pad_2; /* LRU */ > + unsigned long _zd_pad_3; /* LRU */ > + unsigned long _zd_pad_1; /* uses mapping */ > /** @pgmap: Points to the hosting device page map. */ > struct dev_pagemap *pgmap; > unsigned long hmm_data; > - unsigned long _zd_pad_1; /* uses mapping */ > }; > > /** @rcu_head: You can use this to free a page by RCU. */ > > You don't use page->private or page->index, do you Dan? I don't use page->private, but page->index is used by the memory-failure path to do an rmap.