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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 14BA4C433ED for ; Fri, 2 Apr 2021 14:38:12 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1F85C610D1 for ; Fri, 2 Apr 2021 14:38:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F85C610D1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6EE2C8D0002; Fri, 2 Apr 2021 10:38:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 69DD86B0072; Fri, 2 Apr 2021 10:38:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 565558D0002; Fri, 2 Apr 2021 10:38:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0087.hostedemail.com [216.40.44.87]) by kanga.kvack.org (Postfix) with ESMTP id 37F0B6B0071 for ; Fri, 2 Apr 2021 10:38:10 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id DDDB4EFC8 for ; Fri, 2 Apr 2021 14:38:09 +0000 (UTC) X-FDA: 77987681898.07.855C750 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf05.hostedemail.com (Postfix) with ESMTP id A4FF7E000105 for ; Fri, 2 Apr 2021 14:38:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=IWrrySydU1/oVFGzV/01gHMnlvSDnEBCyFAKBNPbXMQ=; b=QqMeM2AuPHvGbfyV9wRQVNM9Ot HlSIsyvwULnCxg6yeJDvnAz4Vk4gxR6GtNNsb8+EVx0zMfGX7SZvRfSLwdRXJi+cFVl+Jr9B6VoRD PS7Qvs+plQiHH3xE+aD86YOHWR059aKwwblgEI0sCQKVQYpVjypwngD9faNWlTm+aG+S64rq+Qs6q 2EX25gt7pixvKE1OMi9mvDr8WcCLqFWiHsu/Fcjdy/4hT3vOK1vEeDbajhZM6fs4axnzSgzSklC8z XkX/9QF8vFgiTKpI75Mj+5FylRHpL5F33mLI7+czjD/lsim0ghd6z5AP3r9UzNc9yaLFDBGjp9bca Y81fkO5Q==; Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lSKvr-007k8s-W3; Fri, 02 Apr 2021 14:37:57 +0000 Date: Fri, 2 Apr 2021 15:37:55 +0100 From: Christoph Hellwig To: Matthew Wilcox Cc: Christoph Hellwig , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-cachefs@redhat.com, linux-afs@lists.infradead.org Subject: Re: [PATCH v6 00/27] Memory Folios Message-ID: <20210402143755.GA1843620@infradead.org> References: <20210331184728.1188084-1-willy@infradead.org> <20210401070537.GB1363493@infradead.org> <20210401112656.GA351017@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210401112656.GA351017@casper.infradead.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: A4FF7E000105 X-Stat-Signature: 6qz7trc8dz9zawpsau5jzxk6nqqm1gxn X-Rspamd-Server: rspam02 Received-SPF: none (casper.srs.infradead.org>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617374288-549025 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 Thu, Apr 01, 2021 at 12:26:56PM +0100, Matthew Wilcox wrote: > On Thu, Apr 01, 2021 at 08:05:37AM +0100, Christoph Hellwig wrote: > > On Wed, Mar 31, 2021 at 07:47:01PM +0100, Matthew Wilcox (Oracle) wrote: > > > - Mirror members of struct page (for pagecache / anon) into struct folio, > > > so (eg) you can use folio->mapping instead of folio->page.mapping > > > > Eww, why? > > So that eventually we can rename page->mapping to page->_mapping and > prevent the bugs from people doing page->mapping on a tail page. eg > https://lore.kernel.org/linux-mm/alpine.LSU.2.11.2103102214170.7159@eggly.anvils/ I'm not sure I like this. This whole concept of structures that do need the same layout is very problematic, even with the safe guards you've added. So if it was up to me I'd prefer the folio as a simple container as it was in the previous revisions. At some point members should move from the page to the folio, but I'd rather do that over a shorter period an in targeted series. We need the basic to go in first.