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 0375FC47071 for ; Thu, 16 Nov 2023 19:40:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 856BE6B0493; Thu, 16 Nov 2023 14:40:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 806A06B0495; Thu, 16 Nov 2023 14:40:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6A7606B0496; Thu, 16 Nov 2023 14:40:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 5BB2C6B0493 for ; Thu, 16 Nov 2023 14:40:30 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 3B17BA0C9E for ; Thu, 16 Nov 2023 19:40:30 +0000 (UTC) X-FDA: 81464834220.09.8CA6EDE Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf29.hostedemail.com (Postfix) with ESMTP id 1D77E12001D for ; Thu, 16 Nov 2023 19:40:27 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Bc7Xkzk6; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf29.hostedemail.com: domain of peterx@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1700163628; 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=Bzv535wMnAruLzQr/48/AxY7g2OnZub15Z3F0evMKPM=; b=v6VhVychlvLfdtN+46TUm0REhIj6Zy/SN04JGiljon8n2Xu/evB5Mr/hVmMNg++gX6KNuP AbrpaA4c0CYwvYGLcGMJQailmLmf4QwgKpr5KAWZSIFbjt2znS5OCsG3ibkKYsDKf35rPt qyBwkQyJWE7Wunk/qF3Z3YbNJVoqVKc= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Bc7Xkzk6; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf29.hostedemail.com: domain of peterx@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=peterx@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1700163628; a=rsa-sha256; cv=none; b=ySWXBQTDim5xZjpOl3RNydNdfFubWj5BroUYTrt9FBVNm8ztHdaEw2ZBxYpuP4SiKW9ey6 HoqsxxM3v/Nw4/e6F2jo94iss1tI7aWE7fbloVSV1i7gaq3QHKWU1y4Qun0svvVxDCn7me tsNhso3yVtPa79SXGzHm8EaQ4s9kI2k= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700163627; 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: in-reply-to:in-reply-to:references:references; bh=Bzv535wMnAruLzQr/48/AxY7g2OnZub15Z3F0evMKPM=; b=Bc7Xkzk6fXiIDJypPVZ0TRP0Qejqwc8R95elAVcTDfjw3Aafawqshj1Y0SxgrjD2BzGhme XoNkYCLkVCzcrTSIpkd9rnTWWy4BKwwEBTUn/8q3yN+Tn4B6XDcCnU/ADOj4VBXGbI5VAf iiWNqwp52kUdNJAC+Dn7NwvuB4ytxIE= Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-587-evS6fHaTNQqvOCFLU5LgFw-1; Thu, 16 Nov 2023 14:40:25 -0500 X-MC-Unique: evS6fHaTNQqvOCFLU5LgFw-1 Received: by mail-qk1-f199.google.com with SMTP id af79cd13be357-77a6f87b78fso13286385a.0 for ; Thu, 16 Nov 2023 11:40:25 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1700163625; x=1700768425; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Bzv535wMnAruLzQr/48/AxY7g2OnZub15Z3F0evMKPM=; b=EDNyx2iDKzjpPxJMpvn300PZBycG9+emjdX1v/DKeD/+oQu/4FQImQRnJSvtD1zXl4 n0sCuMGf/7eE1+uV6fh8kfV2hqull768A4YiHt+cjiNKzdH6uuhvT1KApw+iiwkmN0W+ QrZbVmniqs1NXRzk6kN27dF+7Ckrb3StgJoO/r1Dw+ZhB/rqNfzcwyqThArgPm7dzFSv REACRrHNJgGJ7d9ji+5QNtXKn1RCdq4NpCXapzS+anuHL/VXuBW+rjCl+5PwrWuFo38F wknOPjQK/8+RP4kYKEj4dUBJXZ5SUU3OlviLjxnKy6gi7U8zsejU27p0Ph1SzYTQQz8N Mh8A== X-Gm-Message-State: AOJu0Yy5DnAi+XH3j/uutnLsj11kH/9qrYv/hYFG0sXGzUsCEIITJued GY0xf2WdJSXe6YPUWoDtqC8YfIUO6dWzneIWe+d+4mCMm7DFbsqZAxcgZBVlCx+Ar+RYja+CfQe xYG3gMnYLhDE= X-Received: by 2002:a05:620a:3715:b0:77b:dce8:737 with SMTP id de21-20020a05620a371500b0077bdce80737mr9794674qkb.7.1700163625227; Thu, 16 Nov 2023 11:40:25 -0800 (PST) X-Google-Smtp-Source: AGHT+IH0acypG3gt3orkwfZpo4/rFmSKRN5T9/huxRFJZfE/B/7060gtATTOv/cMrwGWBcYdUNwnHQ== X-Received: by 2002:a05:620a:3715:b0:77b:dce8:737 with SMTP id de21-20020a05620a371500b0077bdce80737mr9794659qkb.7.1700163624980; Thu, 16 Nov 2023 11:40:24 -0800 (PST) Received: from x1n (cpe688f2e2cb7c3-cm688f2e2cb7c0.cpe.net.cable.rogers.com. [99.254.121.117]) by smtp.gmail.com with ESMTPSA id rv4-20020a05620a688400b007756c8ce8f5sm44204qkn.59.2023.11.16.11.40.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Nov 2023 11:40:24 -0800 (PST) Date: Thu, 16 Nov 2023 14:40:21 -0500 From: Peter Xu To: Matthew Wilcox Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mike Kravetz , "Kirill A . Shutemov" , Lorenzo Stoakes , Axel Rasmussen , John Hubbard , Mike Rapoport , Hugh Dickins , David Hildenbrand , Andrea Arcangeli , Rik van Riel , James Houghton , Yang Shi , Jason Gunthorpe , Vlastimil Babka , Andrew Morton Subject: Re: [PATCH RFC 07/12] mm/gup: Refactor record_subpages() to find 1st small page Message-ID: References: <20231116012908.392077-1-peterx@redhat.com> <20231116012908.392077-8-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Stat-Signature: qt881n631md8uix53aeb7shducr7bg8b X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1D77E12001D X-HE-Tag: 1700163627-149014 X-HE-Meta: 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 kDNbaRQC /ROcxV821/3AsbtBfjCGJ380d5VV8hZX8OEFe+Fe1IqC2I/KbA1tmvV6MKNrnpIjZHQeH8m0NvN6CBEkcbsMKLCtk0nNOz0c3Kz+2r+8psK20NpSX2/y/sd3kH1JcJrqX1KN//wJn5wxLIXPUbCqwwqWCNApcYNqQBctYCTdX2dS0RLzSzxM2RSWH5AQibZUEvvPLbD+V7N7TUxJF+PE8OQgs82CCEvw+rQK+4Hmc1g9UW4JS+zX5zCotY3jbSTtopKFaR9VkeZp4uE7tnDpUxdGC8bHMqaOccfzMw6Wp3KAZbjhJ2cy2o4VXFwMaQdNOP5GF+10eI+4ARLF9q11mZXMC9bT+eqTStz8paCGVc7VhoPz6QMWt/6ozkbqYWpv9p19Rr4CyKOkV0rcVg4m2I+9OuJnvMlvXLdmC 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: List-Subscribe: List-Unsubscribe: On Thu, Nov 16, 2023 at 02:51:52PM +0000, Matthew Wilcox wrote: > On Wed, Nov 15, 2023 at 08:29:03PM -0500, Peter Xu wrote: > > All the fast-gup functions take a tail page to operate, always need to do > > page mask calculations before feeding that into record_subpages(). > > > > Merge that logic into record_subpages(), so that we always take a head > > page, and leave the rest calculation to record_subpages(). > > This is a bit fragile. You're assuming that pmd_page() always returns > a head page, and that's only true today because I looked at the work > required vs the reward and decided to cap the large folio size at PMD > size. If we allowed 2*PMD_SIZE (eg 4MB on x86), pmd_page() would not > return a head page. There is a small amount of demand for > PMD size > large folio support, so I suspect we will want to do this eventually. > I'm not particularly trying to do these conversions, but it would be > good to not add more assumptions that pmd_page() returns a head page. Makes sense. Actually, IIUC arm64's CONT_PMD pages can already make that not a head page. The code should still be correct, though. AFAIU what I need to do then is renaming the first field of record_subpages() (s/head/base/) in the next version, or just keep it the old one ("page"), then update the commit message. Thanks, -- Peter Xu