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=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 4CA2CC432BE for ; Tue, 31 Aug 2021 22:16:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A0DD600CD for ; Tue, 31 Aug 2021 22:16:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240595AbhHaWQz (ORCPT ); Tue, 31 Aug 2021 18:16:55 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:55018 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232930AbhHaWQv (ORCPT ); Tue, 31 Aug 2021 18:16:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630448155; 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; bh=87x+DTynGLQU2JkIoM5X3ezVDhZ+h9VNFi3bKAp7/QQ=; b=hDoHHMe2z5XJDohIPeGeWI++lamM/e8S+sNvXjDfH4TZNrK2mlX1jNc5YcUlocnG87w5iT S/R1f6HRYfg1V2AyvRE1L09RY6kH6H/QBOGeXmGi7LobTomd5AGAGIiXx4PfTy0Ikbfzes 7fsPoh+poMyzYlcM2TL+QSxl3FDVcME= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-300-QiOs4Te1P7m56nLit_JQdA-1; Tue, 31 Aug 2021 18:15:53 -0400 X-MC-Unique: QiOs4Te1P7m56nLit_JQdA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 302021009628; Tue, 31 Aug 2021 22:15:51 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.36]) by smtp.corp.redhat.com (Postfix) with ESMTP id E57D26060F; Tue, 31 Aug 2021 22:15:47 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: torvalds@linux-foundation.org, Andrew Morton , Johannes Weiner cc: dhowells@redhat.com, Matthew Wilcox , "Theodore Ts'o" , Christoph Hellwig , Alexander Viro , Vlastimil Babka , Rasmus Villemoes , "Darrick J. Wong" , Dan Williams , Jeff Layton , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Folios: Can we resolve this please? MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3285173.1630448147.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Tue, 31 Aug 2021 23:15:47 +0100 Message-ID: <3285174.1630448147@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Linus, Andrew, Johannes, Can we come to a quick resolution on folios? I'd really like this to be solved in this merge window if at all possible as I (and others) have stuf= f that will depend on and will conflict with Willy's folio work. It would b= e great to get this sorted one way or another. As I see it, there are three issues, I think, and I think they kind of go = like this: (1) Johannes wants to get away from pages being used as the unit of memor= y currency and thinks that folios aren't helpful in this regard[1]. Th= ere seems to be some disagreement about where this is heading. (2) Linus isn't entirely keen on Willy's approach[2], with a bottom up approach hiding the page objects behind a new type from the pov of th= e filesystem, but would rather see the page struct stay the main API ty= pe and the changes be hidden transparently inside of that. I think from what Linus said, he may be in favour (if that's not too strong a word) of using a new type to make sure we don't miss the necessary changes[3]. (3) Linus isn't in favour of the name 'folio' for the new type[2]. Vario= us names have been bandied around and Linus seems okay with "pageset"[4]= , though it's already in minor(-ish) use[5][6]. Willy has an alternate patchset with "folio" changed to "pageset"[7]. With regard to (1), I think the folio concept could be used in future to h= ide at least some of the paginess from filesystems. With regard to (2), I think a top-down approach won't work until and unles= s we wrap all accesses to struct page by filesystems (and device drivers) in wrapper functions - we need to stop filesystems fiddling with page interna= ls because what page internals may mean may change. With regard to (3), I'm personally fine with the name "folio", as are othe= r people[8][9][10][11], but I could also live with a conversion to "pageset"= . Is it possible to take the folios patchset as-is and just live with the na= me, or just take Willy's rename-job (although it hasn't had linux-next soak ti= me yet)? Or is the approach fundamentally flawed and in need of redoing? Thanks, David Link: https://lore.kernel.org/r/YSQSkSOWtJCE4g8p@cmpxchg.org/ [1] Link: https://lore.kernel.org/r/CAHk-=3DwjD8i2zJVQ9SfF2t=3D_0Fkgy-i5Z=3DmQ= jCw36AHvbBTGXyg@mail.gmail.com/ [2] Link: https://lore.kernel.org/r/CAHk-=3DwgkA=3DRKJ-vke0EoOUK19Hv1f=3D47Da6= pWAWQZPhjKD6WOg@mail.gmail.com/ [3] Link: https://lore.kernel.org/r/CAHk-=3DwiZ=3Dwwa4oAA0y=3DKztafgp0n+BDTEV6= ybLoH2nvLBeJBLA@mail.gmail.com/ [4] Link: https://lore.kernel.org/r/CAHk-=3Dwhd8ugrzMS-3bupkPQz9VS+dWHPpsVssrD= fuFgfff+n5A@mail.gmail.com/ [5] Link: https://lore.kernel.org/r/CAHk-=3DwgwRW1_o6iBOxtSE+vm7uiSr98wkTLbCze= 9-7wW0ZhOLQ@mail.gmail.com/ [6] Link: https://lore.kernel.org/r/YSmtjVTqR9%2F4W1aq@casper.infradead.org/ [= 7] Link: https://lore.kernel.org/r/YSXkDFNkgAhQGB0E@infradead.org/ [8] Link: https://lore.kernel.org/r/92cbfb8f-7418-15d5-c469-d7861e860589@rasmu= svillemoes.dk/ [9] Link: https://lore.kernel.org/r/cf30c0e8d1eecf08b2651c5984ff09539e2266f9.c= amel@kernel.org/ [10] Link: https://lore.kernel.org/r/20210826005914.GG12597@magnolia/ [11]