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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B65CEEB64DD for ; Fri, 28 Jul 2023 20:50:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 19AC38D0005; Fri, 28 Jul 2023 16:50:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 14B108D0001; Fri, 28 Jul 2023 16:50:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F2E678D0005; Fri, 28 Jul 2023 16:50:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id E594E8D0001 for ; Fri, 28 Jul 2023 16:50:25 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id C34011607E3 for ; Fri, 28 Jul 2023 20:50:25 +0000 (UTC) X-FDA: 81062213610.15.DB862F6 Received: from mail-ed1-f54.google.com (mail-ed1-f54.google.com [209.85.208.54]) by imf21.hostedemail.com (Postfix) with ESMTP id B49691C0004 for ; Fri, 28 Jul 2023 20:50:23 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b="W/LbinD4"; dmarc=none; spf=pass (imf21.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.54 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1690577423; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=E17cPNd2JHzAg3XLoM3Zw1DUtM3X2m+hWgsCVuqmSVk=; b=36J2nX6dfo1uCnwvdwD4gRRRGZ1eNGHxWU6qJGdk06gU7wBPT7rH4BRvsUnqht4sbQWxJ0 ZEvropLx6L6NXBUqwncrFV7wpFbJxFpxvQWboEUq0EB8PoZzCAgHYnIlQe2mIYBY6tEjp0 lI8dTEY7yGa/uJyxFoUv9p5DBzo9lFY= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b="W/LbinD4"; dmarc=none; spf=pass (imf21.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.54 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1690577423; a=rsa-sha256; cv=none; b=xcK8LPn9eduUKnxg22syZoEMkq/rUvtutc6jJsFi0tA84F+UbVLJHh54OdPpVwowN8Pj3i 05f9Yepuv5KyAViSj/onwmrYEwKLy3K5V6FsH0/Fha5/hJO5M5rLa5uJoOiPZ42QPj/VS/ AN5Qruin8MlxF3DPWQJ1h77rH8Dkn6c= Received: by mail-ed1-f54.google.com with SMTP id 4fb4d7f45d1cf-5221ee899a0so3209388a12.1 for ; Fri, 28 Jul 2023 13:50:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; t=1690577422; x=1691182222; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=E17cPNd2JHzAg3XLoM3Zw1DUtM3X2m+hWgsCVuqmSVk=; b=W/LbinD4Enfk+95f1i9+07bWEIlxhNOTGdsSp2hvp+q9c+rQOMicWs73b9Wav3eRi4 i+0mpmlDo82O4Uv72peL1MmBNa65WF7ZTBM/hcm86AWEdA8cQBljEK56rYh9QIHQQXqv U7yCW/iA41LuPgI06QQPzMk7IKzj0+nxu+Hu8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690577422; x=1691182222; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=E17cPNd2JHzAg3XLoM3Zw1DUtM3X2m+hWgsCVuqmSVk=; b=AlT1ikM/OIOG8VuX+n14/A8hoQph4FH+0VJ8LNDvOngDWacI6xJpR6oaBTf9WOiQWz vtW2X12DsuBzI7JUZm6lVeEm0m8eUAwnvAo9OnIlFmKSNzFP8MmBthcAuPN0VQ48chVI MeA3Lw6LiFn+uSuLx1daimcOVEZNRt0gXwHJZSuq/OghLYUzeKpahfRIUJuwlwJ7hVlT sU6NNJEtKKBBz2MhIEJ3UzKqwVcf+EA3sakqAq0WfJALbOaqfGtbIGzz0nZ6NHCb1SxH XusUU3NGUJNBJg3jsMIx4uSypqeGbYyWo+Wj3AlfIfK0Z2LsBTpqIFpevqE0cNhgC1sl DNyA== X-Gm-Message-State: ABy/qLZOdIBaAa9xyADVidpDzti/ajGfpcYPI4njJ/KJBMZx9O2pMopO cuC6XSpeQvVtT6yEFuTDkoHOb0G6jXyOHWsegHrkYnE1 X-Google-Smtp-Source: APBJJlFxe8axkSP7Qz2b3Y33TpgaDCHPt3X+7YMng5zwnkDzcz6vCHQMCvL9Ytt5WiwCfqJZyr3QgQ== X-Received: by 2002:a05:6402:1b0e:b0:522:4d16:752 with SMTP id by14-20020a0564021b0e00b005224d160752mr2328205edb.21.1690577421910; Fri, 28 Jul 2023 13:50:21 -0700 (PDT) Received: from mail-ed1-f52.google.com (mail-ed1-f52.google.com. [209.85.208.52]) by smtp.gmail.com with ESMTPSA id b8-20020aa7c908000000b0052255cbad8dsm2172959edt.94.2023.07.28.13.50.21 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Jul 2023 13:50:21 -0700 (PDT) Received: by mail-ed1-f52.google.com with SMTP id 4fb4d7f45d1cf-51d95aed33aso3190909a12.3 for ; Fri, 28 Jul 2023 13:50:21 -0700 (PDT) X-Received: by 2002:aa7:dcc6:0:b0:51e:2a1b:6de with SMTP id w6-20020aa7dcc6000000b0051e2a1b06demr2181151edu.40.1690577420993; Fri, 28 Jul 2023 13:50:20 -0700 (PDT) MIME-Version: 1.0 References: <20230727212845.135673-1-david@redhat.com> In-Reply-To: From: Linus Torvalds Date: Fri, 28 Jul 2023 13:50:03 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v1 0/4] smaps / mm/gup: fix gup_can_follow_protnone fallout To: David Hildenbrand Cc: Peter Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Andrew Morton , liubo , Matthew Wilcox , Hugh Dickins , Jason Gunthorpe , John Hubbard Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Stat-Signature: wc67z38ki3k5euybe97gnjbuotmratse X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B49691C0004 X-HE-Tag: 1690577423-946605 X-HE-Meta: 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 2+Hpq3ON 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 28 Jul 2023 at 13:33, David Hildenbrand wrote: > > So would you rather favor a FOLL_NUMA that has to be passed from the > outside by selected callers or a FOLL_NUMA that is set on the GUP path > unconditionally (but left clear for follow_page())? I'd rather see the FOLL_NUMA that has to be set by odd cases, and that is never set by any sane user. And it should not be called FOLL_NUMA. It should be called something else. Because *not* having it doesn't disable following pages across NUMA boundaries, and the name is actively misleading. It sounds like what KVM actually wants is a "Do NOT follow NUMA pages, I'll force a page fault". And the fact that KVM wants a fault for NUMA pages shouldn't mean that others - who clearly cannot care - get that insane behavior by default. The name should reflect that, instead of being the misleading mess of FOLL_FORCE and bad naming that it is now. So maybe it can be called "FOLL_HONOR_NUMA_FAULT" or something, to make it clear that it's the *opposite* of FOLL_FORCE, and that it honors the NUMA faulting that nobody should care about. Then the KVM code can have a big comment about *why* it sets that bit. Hmm? Can we please aim for something that is understandable and documented? No odd implicit rules. No "force NUMA fault even when it makes no sense". No tie-in with FOLL_FORCE. Linus