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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 6E659C433B4 for ; Thu, 1 Apr 2021 18:37:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 467A160FDA for ; Thu, 1 Apr 2021 18:37:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235926AbhDAShP (ORCPT ); Thu, 1 Apr 2021 14:37:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36684 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239204AbhDASPm (ORCPT ); Thu, 1 Apr 2021 14:15:42 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 15637C05BD11; Thu, 1 Apr 2021 05:52:14 -0700 (PDT) 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=Yw41C/LM/CLkV/f2jz3URlFrp1rmhB03Zhe1Y9zc6w8=; b=VReZDpDt5aNf6kSFMIIU9tiZ9p 5jBuVEp/WF4EuLT2Hz8powvl9pghjOFAizPU5QqGxMcTSuk5AlVDG7Rzp7vHscBL2WL0TQuQJcoNB x0M3qRg4kpC0vTnXlJxgPn+72DK0T1eUYtuMoLu8e/A6IiEJjVLlfctuB6CPjCh5eyenHHWvzrU0L o0P6LZ0dsT4WJsi6JYfJt8nhNvLEzQAZpr4sOcMV4YaUBxdSKHBZhfHmOzrLSXhxZx45e1jrHyrBC AKzBk8cRUSNvLbtv2B6nLwhzd1qQAd5DocwjB1H1ixZjYvH5kwC1SLLmit+KJ9coSwn2UTs06N8Ya UZqijUyQ==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lRwnp-0068jn-3I; Thu, 01 Apr 2021 12:52:05 +0000 Date: Thu, 1 Apr 2021 13:52:01 +0100 From: Matthew Wilcox To: Jason Gunthorpe 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: <20210401125201.GD351017@casper.infradead.org> References: <20210331184728.1188084-1-willy@infradead.org> <20210401070537.GB1363493@infradead.org> <20210401112656.GA351017@casper.infradead.org> <20210401122803.GB2710221@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210401122803.GB2710221@ziepe.ca> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 01, 2021 at 09:28:03AM -0300, Jason Gunthorpe wrote: > 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/ > > Is that gcc structure layout randomization stuff going to be a problem > here? > > Add some > static_assert(offsetof(struct folio,..) == offsetof(struct page,..)) > > tests to force it? You sound like the kind of person who hasn't read patch 1. diff --git a/mm/util.c b/mm/util.c index 0b6dd9d81da7..521a772f06eb 100644 --- a/mm/util.c +++ b/mm/util.c @@ -686,6 +686,25 @@ struct anon_vma *page_anon_vma(struct page *page) return __page_rmapping(page); } +static inline void folio_build_bug(void) +{ +#define FOLIO_MATCH(pg, fl) \ +BUILD_BUG_ON(offsetof(struct page, pg) != offsetof(struct folio, fl)); + + FOLIO_MATCH(flags, flags); + FOLIO_MATCH(lru, lru); + FOLIO_MATCH(mapping, mapping); + FOLIO_MATCH(index, index); + FOLIO_MATCH(private, private); + FOLIO_MATCH(_mapcount, _mapcount); + FOLIO_MATCH(_refcount, _refcount); +#ifdef CONFIG_MEMCG + FOLIO_MATCH(memcg_data, memcg_data); +#endif +#undef FOLIO_MATCH + BUILD_BUG_ON(sizeof(struct page) != sizeof(struct folio)); +} + struct address_space *page_mapping(struct page *page) { struct address_space *mapping;