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 3D98AEB64D8 for ; Wed, 14 Jun 2023 15:47:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 935BF6B0074; Wed, 14 Jun 2023 11:47:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8E6286B0075; Wed, 14 Jun 2023 11:47:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 788586B0078; Wed, 14 Jun 2023 11:47:39 -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 64A7E6B0074 for ; Wed, 14 Jun 2023 11:47:39 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 1BE0D1A071D for ; Wed, 14 Jun 2023 15:47:39 +0000 (UTC) X-FDA: 80901783438.25.81F9FDB Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf14.hostedemail.com (Postfix) with ESMTP id CBF5C100005 for ; Wed, 14 Jun 2023 15:47:36 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hNaOe1bE; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf14.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1686757656; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=8bW8qcFrRQFmvEEYodNH2D88CTYW+Ip8JaHIZ5ITPGk=; b=WAjlC9KKPda45g5MhVoihjy6l59dsVNVM6fIpKRkaU1WC2mUJNhWOYRniNZdCqOkmy0gD2 xfucgGNcKySRKq+8A5oHb59FN4/WOzTxyp2NNOrqM3qKY3/jUCrfXHf5/Me29KHawT4Lml 48WScq2NhxmvCGgn2WTPk1qORu+l4Dc= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=hNaOe1bE; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf14.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686757656; a=rsa-sha256; cv=none; b=8Txw1UJPikgZUcLtNGOrcUNwL99BVRtGaRxT926CtFrvkn0Z4/XlYEvdXz7CO6Qfp1Ogi9 q6xbCkXbYalS6408+CCbK8AZkHTfcS0cTIttoWW4yPU6INohEV4dHp0+SZgyo41L9bgpmd uEYkdlL95jDl2gMMTd+hvA5p/gBI+mE= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1686757656; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8bW8qcFrRQFmvEEYodNH2D88CTYW+Ip8JaHIZ5ITPGk=; b=hNaOe1bEKWN1VKZEkrh8RLv2dMEA05fW9EmoSl8npYplplcFFtWgNXikAaC+8b+TKUy8b6 gCiWUbookxAuAh5ekkrn9h/djsCO9gbMKwn3mEXzzJkyUQSFHgQENlpAtkU0gcCpM4t+E2 x/lkWf+ZgyG4QSmdW7MjVGl6BQPrwW8= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-573-Nps839FyMT29RtZLlsGxlA-1; Wed, 14 Jun 2023 11:47:35 -0400 X-MC-Unique: Nps839FyMT29RtZLlsGxlA-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-3f739a73ba4so3657665e9.3 for ; Wed, 14 Jun 2023 08:47:34 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686757654; x=1689349654; h=content-transfer-encoding:in-reply-to:organization:from:references :cc:to:content-language:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=8bW8qcFrRQFmvEEYodNH2D88CTYW+Ip8JaHIZ5ITPGk=; b=QGXCOKQp63Ii5N/LF37XAmkO7Asxb/+fMysS3hhhx9MLaOt1OWrsV1/uoWEmcsTINi sp6vRIiX3G/6I6srShtCXMMtqNtbD/en6zJaR89JwzqAuxjflENIxeiZGy0PzKn7+Zo1 ekaIkOrhoUbgjGAO+NrRliMMnGuQdzihCef86IVrHbadn6ahkZ+4CLCtBUfrHYbbol2l 6Hm3TOllVGmgRrt4Kh66basktTQzh5ymh/aGnKjfwjrDbcWO5mQ80Bw4FrgI/HiFkuZ5 Tpt4cw8oXUYsdGZa/mo1Dhp9jABh6zzs9vdhBM1ZHH0XrBpKs8SwZb9ywTEwpl1HRh3R selQ== X-Gm-Message-State: AC+VfDzF3iJYAEZJpMsA98aPnv44QelvZV7Gb/5pYD6LUhD3HodBLX2q I+dYo7dMsDQwSjRuc+TFw1ubtfncKpFef77Z0mmCIMAbqXQ4myUuP9HrnZboHK6n9jhVragJy6b 8ZOEV/BbEHno= X-Received: by 2002:a1c:f70a:0:b0:3f5:1728:bde9 with SMTP id v10-20020a1cf70a000000b003f51728bde9mr10045593wmh.2.1686757653912; Wed, 14 Jun 2023 08:47:33 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ5vMyBEpvendEjmQQmDpIA7ahOUPL61Q5ZmleywrLEPvlNH9zFyI/8J+qQq+DFBveSCxMebSA== X-Received: by 2002:a1c:f70a:0:b0:3f5:1728:bde9 with SMTP id v10-20020a1cf70a000000b003f51728bde9mr10045570wmh.2.1686757653365; Wed, 14 Jun 2023 08:47:33 -0700 (PDT) Received: from ?IPV6:2003:cb:c704:b200:7d03:23db:ad5:2d21? (p200300cbc704b2007d0323db0ad52d21.dip0.t-ipconnect.de. [2003:cb:c704:b200:7d03:23db:ad5:2d21]) by smtp.gmail.com with ESMTPSA id 17-20020a05600c22d100b003f8044b3436sm17453217wmg.23.2023.06.14.08.47.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Jun 2023 08:47:32 -0700 (PDT) Message-ID: <38574ed3-ea96-a72e-00dd-4e6204413a86@redhat.com> Date: Wed, 14 Jun 2023 17:47:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH 4/7] mm/hugetlb: Prepare hugetlb_follow_page_mask() for FOLL_PIN To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox , Andrea Arcangeli , John Hubbard , Mike Rapoport , Vlastimil Babka , "Kirill A . Shutemov" , Andrew Morton , Mike Kravetz , James Houghton , Hugh Dickins References: <20230613215346.1022773-1-peterx@redhat.com> <20230613215346.1022773-5-peterx@redhat.com> <533c32cf-9a18-1590-4d29-f076d6bd58c1@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: CBF5C100005 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: d33e35y7azx6kzp1kx6yqmwibshi1zpd X-HE-Tag: 1686757656-990422 X-HE-Meta: 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 7sE8gSDH 4mVc6A6QYpb6VfDtGn1Wg1XyHX3O2SQlYIJVBAcIlVvKpu3eSD+YaZQ7nrPFhGH5LGl5NvaDYlOMcMDiRjaf7lumtWpyQupjnkxAN2RZpMkznSzBZX+hg5EZ8dWcLJjjSWUI53VzKRLBSXw5vyoe1S/v+ZPZ5t8dxsTMMDDp94bLq9HqhmNgUQbWLcfEJMm7fnawSxPTCQhaYp4LtwubfOIoTXfm11pUm3VYROajzdaesde8HKOicsUiXwRJmNi+FYaQnc8fbvkRYSo/sJccgKmVlw1xc8kj7lCx0hn7ZO6hK6ntWNsKJHLvUnHhiQON8SuLrDt4ogCIyaK36FGa46A8nyb6zipwqU+1nv1Euiy7Xd5ALtu4D+BVgx0b7XdE/iRainvFy13kL2GjO35VJlfn7AQj7m8fw9p8ZnyW5nju8q1sVbQ+ez1XErnIP7+bF9JmdfKfEaabq4p4= 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 14.06.23 17:31, Peter Xu wrote: > On Wed, Jun 14, 2023 at 05:17:13PM +0200, David Hildenbrand wrote: >> On 14.06.23 17:11, Peter Xu wrote: >>> On Wed, Jun 14, 2023 at 04:57:37PM +0200, David Hildenbrand wrote: >>>> On 13.06.23 23:53, Peter Xu wrote: >>>>> It's coming, not yet, but soon. Loose the restriction. >>>>> >>>>> Signed-off-by: Peter Xu >>>>> --- >>>>> mm/hugetlb.c | 7 ------- >>>>> 1 file changed, 7 deletions(-) >>>>> >>>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>>> index f037eaf9d819..31d8f18bc2e4 100644 >>>>> --- a/mm/hugetlb.c >>>>> +++ b/mm/hugetlb.c >>>>> @@ -6467,13 +6467,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, >>>>> spinlock_t *ptl; >>>>> pte_t *pte, entry; >>>>> - /* >>>>> - * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via >>>>> - * follow_hugetlb_page(). >>>>> - */ >>>>> - if (WARN_ON_ONCE(flags & FOLL_PIN)) >>>>> - return NULL; >>>>> - >>>>> hugetlb_vma_lock_read(vma); >>>>> pte = hugetlb_walk(vma, haddr, huge_page_size(h)); >>>>> if (!pte) >>>> Did you fix why the warning was placed there in the first place? (IIRC, at >>>> least unsharing support needs to be added, maybe more) >>> >>> Feel free to have a look at patch 2 - it should be done there, hopefully in >>> the right way. And IIUC it could be a bug to not do that before (besides >>> CoR there was also the pgtable permission checks that was missing). More >>> details in patch 2's commit message. Thanks, >> >> Oh, that slipped my eyes (unsharing is not really a permission check) -- and > > I think it is still a "permission check"? It means, we forbid anyone R/O > taking the page if it's not exclusively owned, just like we forbid anyone > RW taking the page if it's not writable? Agreed, just not in the traditional PTE-protection case. > > It's just that the permission check only applies to PIN which follow_page() > doesn't yet care, so it won't ever trigger. > >> the patch description could have been more explicit about why we can now >> lift the restrictions. >> >> For the records: we don't use CoR terminology upstream. As suggested by >> John, we use "GUP-triggered unsharing". > > Sure. > >> >> As unsharing only applies to FOLL_PIN, it doesn't quite fit into patch #2. >> Either move that to this patch or squash both. > > Sure, no strong opinions here. > > The plan is _if_ someone wants to backport patch 2, this patch should not > be part of it. But then maybe it makes more sense to move the CoR change > there into this one, not because "it's not permission check", but because > CoR is not relevant in follow_page(), so not relevant to a backport. Right. Then just call patch #2 "Add missing write-permission check" and this patch "Support FOLL_PIN in hugetlb_follow_page_mask()" or sth. like that. Regarding the backport, I really wonder if patch #2 is required at all, because I didn't sport any applicable FOLL_WRITE users. Maybe there were some? Hm. If it's not applicable, a single "Support FOLL_PIN in hugetlb_follow_page_mask()" patch might be cleanest. -- Cheers, David / dhildenb